In the mobility of the future, energy recovery plays an increasingly important role, including that which can be achieved through the suspension of a car. Audi is working on a prototype called "eROT", in which electromechanical rotary shock absorbers replace the telescopic hydraulic shock absorbers used today, to save fuel and provide even greater comfort.
The principle behind the eROT is easily explained: “Every bump, every bump, every curve induces kinetic energy in the car. Today's shock absorbers absorb that energy, which is lost as heat, ”explains Stefan Knirsch, Director of Technical Development at AUDI AG. “With the new electromechanical damper together with the 48-volt electrical system, we put that energy to use. The system also gives us and our customers entirely new possibilities when it comes to adjusting the suspension. "
The eROT system responds quickly and with minimal inertia. As an actively controlled suspension, it is ideally suited to the unevenness of the tread surface and the user's riding style. A damping setting that can be defined virtually unlimitedly by software increases the functional possibilities. Eliminates the mutual dependence on extension and compression displacements that limits conventional hydraulic shock absorbers.
With the eROT, Audi configures the compression movement for comfort without compromising rebound travel. Another advantage of the new damping system is its geometry. Electric motors arranged horizontally in the area of the rear axle replace the vertical telescopic shock absorbers, allowing additional space in the trunk.
The eROT system enables a second function, in addition to the ability to freely program damping: it can convert the kinetic energy created in compression and extension into electricity. To achieve this, an arm absorbs the movement of the wheel. This arm transmits the force through a group of gears to an electric motor, which converts it into electricity.
The recovery capacity is, on average, between 100 and 150 watts in tests carried out on German roads - from 3 watts on well paved motorways to 613 watts on a bumpy secondary road - which in normal use conditions corresponds to CO2 savings of up to three grams per kilometer.
The new eROT technology is based on a 48 volt electrical subsystem. In the prototype configuration, its lithium-ion battery offers a capacity of 0,5 kilowatt-hours and a maximum power output of 13 kilowatts. A DC converter connects the 48-volt subsystem to the main 12-volt electrical system, which includes a high-efficiency generator.
Initial test results for eROT technology are promising, and it would therefore be possible to use it in future Audi series models. A prerequisite for this is the 48-volt electrical system, currently a key technology in Audi's electrification strategy.
In the next evolution, planned for 2017, the 48-volt system will serve as the primary electrical system in a new model from the brand with the four rings, which will use a high-performance light hybrid system, offering potential fuel savings of up to 0,7 liters per 100 kilometers.