New technology from Audi aims to ease the pain of driving on rough roads, in more ways than one. The company is working on a prototype called eROT, in which electromechanical rotary dampers replace the hydraulic dampers used today for an even more comfortable ride.
The principle behind eROT is explained by Dr.-Ing. Stefan Knirsch, board member for technical development : “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. 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 technology is based on a high-output 48 V 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 V electrical subsystem to the 12 V primary electrical system, which includes a high-efficiency, enhanced output generator.
eROT 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.
The system allows Audi to configure 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.
The eROT system enables a second function besides the freely programmable damper characteristic: It can convert the kinetic energy during compression and rebound into electricity. To do this, a lever arm absorbs 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 W on average during testing on German roads – from 3 W on a freshly paved freeway to 613 W on a rough secondary road. Under customer driving conditions, this corresponds to CO2 savings of up to three grams per kilometre.
Audi says that, since initial test results for eROT technology are promising, its use in future production models is plausible. A prerequisite for this is the 48 V electrical system, which is a central component of the company’s electrification strategy. In the next version planned for 2017, the 48 V 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 litres per 100 kilometres.