Audi comes up with a new way to recuperate energy from suspension systems

Car electrification isn’t something that is going to go away. In fact, it’s something automakers are striving to increase on a wide scale every day. See, we’re actually working against ourselves when you really think about it. As our technology evolves so does our demand for power, which is a serious problem when it comes to electrification of cars. To put it simply, the more electronics, the more power is used, and ultimately, the fewer all-electric miles we can travel with an electrified vehicle. So, we need to come up with new innovations and solutions to help store energy more efficiently and recuperate energy that is lost during braking and other scenarios. The latest company to come up with a breakthrough in energy recuperation is Audi with its “eROT” system.

eROT is basically an electrical suspension system that uses electric motors and electrical dampers (shocks) to absorb energy as our cars travel over bumps and holes in the road. With the traditional, hydraulic dampers used on cars today, the energy from bumps and potholes is converted to heat and dispersed by the metal housing of the damper itself. But, eROT, uses a combination of electric motors and a 48-volt electrical system to absorb the energy and turn it into electrical power.

Stephen Knirsch, Board Member for Technical Development at Audi AG, said, “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.”

There are multiple benefits to the eROT system. First, the unique mounting of the system allows for more cargo room in the rear, plus the eROT system is actively controlled. This means it adapts to irregularities in the road as well as the driver’s specific driving style to supply the best ride possible. According to Audi, the average rate of recuperation during testing thus far comes in at an average of 100 to 150 watts. Freshly paved highway offers the least – around 3 watts – while rough secondary roads can increase recuperation up to as much as 613 watts. The system’s current configuration includes a 0.5-kilowatt hour lithium ion battery that has a peak output of 13 kilowatts. The energy is then passed through a DC Converter which drops the voltage down to be passed into the 12-volt primary electrical system.

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Why it matters

At this point, the eROT system is still in the prototype stages, but Audi has seen pretty spectacular results so far. It’s certainly plausible that we could see this system move into production and eventually into various Audi models. The most important thing about the system is that 48-volt electrical system, which is the foundation of Audi’s electrification strategy anyway.

By 2017, Audi will be testing this system on a model with a 48-volt primary system (as opposed to the 12-volt system in most cars today) with the eROT system supplying power to a high-performance mild hybrid drive system. Audi claims that the system can offer a fuel savings of 0.7 liters per 100 kilometers, however, we’ll hold judgment of that one until we see some real world testing results.

Press Release

In the mobility of the future, the recuperation of energy plays an increasingly important role, including in a car’s suspension. Audi 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 easily explained: “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,” said 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 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.

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 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.

Initial test results for the eROT technology are promising, 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.

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