Audi spoke about all-wheel drive quattro for electric carsAugust 12, 2020
For four decades, Audi has been setting the pace with quattro permanent all-wheel drive and thus pioneering a paradigm shift in powertrain technology in the automotive world and in motorsport. Audi is now using the knowledge it has accumulated in this area since 1980 to take the next step.
The electric quattro in the e-tron range marks another step for Audi in the era of electromobility. Driving pleasure and efficiency combined in one package. The company mass-produces an all-wheel-drive system that is highly variable, agile and precise, while making efficient use of available energy.
“For us, the electric quattro is the perfect combination of performance and high efficiency. We combine the benefits of drive axle efficiency with the traction and dynamic performance of an AWD system, ”says Michael Vine, Project Manager for Four Wheel Drive Control Systems.
In the current e-tron models, all of the torque is transferred to the rear wheels, while the engine on the front axle is simultaneously de-energized. Since the motor is an induction type, there is no internal electrical resistance loss, so this drive circuit consumes little power. The front axle – within milliseconds and unnoticed by the driver – is activated only as needed, for example, when high driving dynamics, high torque transmission are required or in case of a low coefficient of friction due to dirt or snow under the wheels.
Audi engineers combine features such as electric torque vectoring on the rear axle, selective wheel torque control via mechanical differential braking and high recuperation efficiency in an electric powertrain. In addition, drivers can customize the high variability of the system according to their personal preferences through individual program selection.
Compared to mechanical four-wheel drive, the presence of an electric motor on each axle provides a faster response of the drive system. For example, the delay in the case of electric torque vectoring – in other words, the time interval between sensor measurement and active torque distribution – is only 30 milliseconds. This is almost 75% faster than the response time of a mechanical system. In addition, electric actuators provide clearly higher levels of torque. Up to 220 Nm more torque can be transmitted to the outer wheel in a corner.
When the coefficient of friction on snow or ice is low, traction can also be optimized with great precision: the corresponding coefficient of friction of the driven wheels is measured and, thanks to the distribution of the torque, is used optimally, thereby increasing the overall thrust.
Smart control is a prerequisite for this software function. The Drive Control Unit (DCU) distributes the torque to the motors. The electronic chassis platform (ECP) integrating control unit uses the sensor signals to monitor the vehicle’s driving conditions and calculates the ideal longitudinal and lateral torque distribution.
Traction Control (TCR) operates at one millisecond intervals. This is made possible by transferring the individual functional components of the Electronic Stability Control (ESC) to the power electronics directly on the electric motors. The drive control unit coordinates the traction control and the all-wheel drive controller, with the engineers prioritizing agility and a sporty base layout.
Drivers can customize the electric quattro to their liking using two controllers. The Audi drive select system, which is standard on e-tron models, offers 7 pre-configured profiles: Comfort, Automatic, Dynamic, Economy, Individual, Allroad and Offroad. Thus, among other things, the electric all-wheel drive, as well as the suspension and other systems, can be adapted to the road conditions and personal preferences of the driver.
Electronic Stability Control (ESC) has 4 programs: Normal, Sport, Offroad and Off. Off-road, it optimizes stability, traction and brake management, and activates the standard hill descent control. In addition, drivers can select three levels of recuperation: at level 0, the car is coasting, at level 1, the car slows down a little, and at level 2, which has a deceleration range of up to 0.13 g and recovers the most energy, the driver will feel significant braking. equivalent to pressing hard on the brake pedal. In manual mode, the vehicle retains the previously selected recuperation level.
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