Audi sends a charge through suspension thinking

Future eROT suspension system replaces shocks with electric motors

Published: August 11, 2016, 1:15 PM
Updated: October 11, 2021, 10:02 AM

Audi eROT system rear axle

Audi is experimenting with a new suspension system that replaces the traditional shock absorber we know with an electric motor.

Called eROT (for Electromechanical ROTary), the system applies the principles of energy recuperation to the suspension system, with the aforementioned electromechanical rotary dampers replacing the hydraulic dampers common today, with the end result being better adjustment of damping for an amazingly comfortable ride.

“Every pothole, every bump, every curve induces kinetic energy in the car. Today’s dampers absorb this energy, which is lost in the form of heat,” explained Dr.-Ing. Stefan Knirsch, Board Member for Technical Development at AUDI AG. “With the new electromechanical damper system in the 48-volt electrical system, we put this energy to use. It also presents us and our customers with entirely new possibilities for adjusting the suspension.”

The system is able to respond far more quickly than fluid-filled shocks (even the electrically charged ones of active suspensions). It adapts freely to road imperfections and to the driving style, with that control then defined by software, while eliminating the correlation between compression and rebound strokes of a traditional shock (that “what goes up must come down” or “for every action, there’s an opposite reaction” principle of physics).

With eROT, Audi can soften the compression stroke without the compromising firmness of the rebound stroke. And as a bonus, the horizontal arrangement of the electric motors in the chassis allows increased space in the luggage and engine compartments over that used by conventional upright telescopic shocks.

But there are more benefits. It would become an important component of an automated driving experience, with yet another “drive by wire” component that could be controlled by a computer entrusted with the operation of a vehicle. And, it might also help recover energy for use in other vehicular functions.

The lever arm that absorbs the motion of the wheel, does it through a series of gears and transmits the force to an electric motor to turn it into electricity. Audi figures the recuperation output is in the neighbourhood of 100-150 watts (depending on the level of roughness), figuring the system could recover 3 watts on a freshly paved highway and upwards of 600 watts on a country road. The company extrapolates those figures to a CO2 savings of up to 3 g/km.

The technology is part of a high-output 48-volt electrical system, with a lithium ion battery offering energy capacity of 0.5 kWh and putting out a peak of 13 kW. A direct current converter connects the electrical system to the vehicle’s 12-volt primary system (which also includes an enhanced output generator).

The electrical system is a central component in Audi’s future electrification plans, with the next vehicle (coming in 2017) having the 48-volt electrical system as the primary electrical system that will be used for a mild hybrid drive system (to potentially reduce fuel consumption by 0.7 L/100km).