A Return to Rotary Dampers?
Friday, August 12, 2016 at 12:00AM ;)
If you own an old British sports car, you may be familiar with lever-arm rotary dampers. These shock absorbers did an okay job, but did not have the broadband control of today’s upright hydraulic telescopic dampers. So why would Audi be looking at replacing today’s design with one from the past? Two words: energy recuperation.
Audi calls the prototype eROT. In it a lever arm absorbs the motion of the wheel hub, and transfers it by means of a series of gears to an electric motor that turns this motion into electrical energy. Audi says the average recuperation output is 100 to 150 watts on German roads. This varies from three watts on a freshly paved surface to 613 watts on a rough secondary road. Central to this system is a high-output 48-volt electrical system that is connected to the car’s 12-volt electrical system by a DC converter. A lithium-ion battery with an energy capacity of 0.5 kWh and peak output of 13 kilowatts stores and releases the energy produced by the dampers.
That output is needed because eROT is an active suspension that decouples the compression and rebound strokes, and uses the recovered energy to control wheel movement. This, Audi claims, increases the functional scope of damper control, which is freely definable via software. Thus, the compression stroke can be kept comfortably soft while the rebound stroke is taut. And, with the high system output, real-time millisecond control of wheel travel can be achieved.
In addition, because the electromechanical dampers package horizontally and are physically connected to the wheel at the lowest point of the hub carrier, the space reserved for conventional upright telescopic dampers can be eliminated, and the new design packaged behind the rear axle line. Similarly, a front eROT unit would take the place of a suspension lower arm. — CAS