Audi developing electromechanical rotary dampers; potential for energy recuperation from suspension; 48V
Audi is developing a prototype electromechanical rotary dampening system called “eROT,” in which electromechanical rotary dampers replace the hydraulic dampers used today for an even more comfortable ride. The eROT system also offers the potential for energy recuperation from the suspension.
Every pothole, bump, and curve in the road induces kinetic energy during compression and rebound of the car’s suspension, observes Dr.-Ing. Stefan Knirsch, Board Member for Technical Development at AUDI AG. “Today’s dampers absorb this energy, which is lost in the form of heat. 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.”
|Audi’s prototype eROT system. Click to enlarge.|
The eROT system responds quickly and with minimal inertia. As an actively controlled suspension, it adapts ideally to irregularities in the road surface and the driver’s driving style.
A damper characteristic that is virtually freely definable via software increases the functional scope. It eliminates the mutual dependence of the rebound and compression strokes that limits conventional hydraulic dampers. With eROT, Audi configures the compression stroke to be comfortably soft without compromising the taut damping of the rebound stroke.
Another advantage of the new damper system is its geometry. The horizontally arranged electric motors in the rear axle area replace the upright telescopic shock absorbers, which allows for additional space in the luggage compartment.
To convert the kinetic energy during compression and rebound into electricity, eROT uses a lever arm to absorb the motion of the wheel carrier. The lever arm transmits this force via a series of gears to an electric motor, which converts it into electricity.
The recuperation output is 100 to 150 watts on average during testing on German roads—from 3 watts on a freshly paved freeway to 613 watts on a rough secondary road. Under customer driving conditions, this corresponds to a CO2 savings of up to three grams per kilometer (4.8 g/mi).
The new eROT technology is based on a high-output 48-volt electrical system. As currently configured, its lithium-ion battery offers an energy capacity of 0.5 kilowatt hours and peak output of 13 kilowatts. A DC converter connects the 48-volt electrical subsystem to the 12-volt primary electrical system, which includes a high-efficiency, enhanced output generator.
Audi said that initial test results for the eROT technology are promising, and thus its use in future Audi production models is “certainly plausible.” A prerequisite for this is the 48-volt electrical system, which is a central component of Audi’s electrification strategy.
In the next version planned for 2017, the 48-volt system will serve as the primary electrical system in a new Audi model and feed a high-performance mild hybrid drive. It will offer potential fuel savings of up to 0.7 liters per 100 kilometers.