Audi Develops Innovative Shock Absorber System

Audi is leading the way when it comes to improving fuel economy through modifications to a car’s suspension. The company is currently working on a prototype named “eROT,” which differs from a conventional shock absorber system by using electromechanical rotary dampers instead of hydraulic dampers. This will go a long way towards improving fuel economy and enhancing ride comfort.

According to Dr.-Ing. Stefan Knirsch, Board Member for Technical Development at AUDI AG, when vehicles go over bumps, curves and potholes, kinetic energy is created and this energy is dissipated in the form of heat. The new electromechanical damper system in the 48-volt electrical system will minimize the dissipation of this energy and convert it into a usable form. It also gives rise to new ways in which the suspension could be adjested to make the ride smoother.

The eROT system is highly responsive and offers minimal inertia. It is an actively controlled suspension that easily adapts to even highly irregular road surfaces and to individual driving styles. The characteristics for the damper can also be defined through software thus giving it greater functional scope. One of the characteristics of the conventional hydraulic dampers that are currently used is the mutual dependence of the rebound and compression strokes. In the eROT system it is possible to configure the compression stroke so that it is soft without compromising the taut damping of the rebound stroke. Another defining characteristic of the new damper system is its shape and dimensions. Upright telescopic shock absorbers are replaced by the horizontally arranged electric motors in the rear axle area freeing up additional space in the luggage compartment.

In addition to the freely programmable damper characteristic, the eROT system can convert the kinetic energy during compression and rebound into electricity through a lever arm that absorbs the motion of the wheel carrier. The lever arm transmits this force through an arrangement of gears to an electric motor, that converts this kinetic energy into electricity. During tests conducted on German roads, the recuperation output is an average of 100 to 150 watts, ranging from 3 watts on a smooth freeway to 613 watts on a rough inner road. This can correspond to a CO2 savings of up to three grams per kilometer.

As its basis, the new eROT technology uses a high-output 48-volt electrical system. 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.

The first test results for the eROT technology show a lot of promise and it definitely looks like this will soon be seen in future Audi production models. One of the roadblocks is proper development of the the 48-volt electrical system, which is a central component of Audi’s electrification strategy. In the next version of the system that is planned for 2017, the 48-volt system be the primary electrical system for a new model from Audi and will also be one of the components of a high-performance mild hybrid drive. It will offer potential fuel savings of up to 0.7 liters per 100 kilometers.