Fraunhofer Adaptronics Alliance

Development and test of an active engine mount

Image 1: Active engine mount 2nd Generation

In vehicles, engines cause vibrations that are transferred from the mounts and the adjacent structures to the interior whe­re they typically result in unwanted sound emissions. Current developments in the automotive industry such as three-cylinder engines and the use of cylinder deactivation are leading to an increase in vibration levels that passive systems can no longer compensate for. The implementation of active systems is a promising approach to improve vibration comfort and the acoustic impression. In vehicles the loads acting on the mounts can be divided into dynamic and static or quasi-static components. The quasi-static components consist of the en­gine-mass as well as the driving torque. These loads may exceed the dynamic loads, which are most significant in terms of dri­ving comfort and primarily result from the combustion process as well as inertia forces, by orders of magnitude. However, the static loads do not have any effect on the vibration of the car body.

Existing active mounting systems often utilize a serial arrangement of an actuator and a passive elastic coupling element. However, such a serial arrangement of the actuator with the suspension spring carries the disadvantage that the actuator is fully exposed to the static loads. This usually results in both, an unnecessarily large actu­ator and high power requirement. A smart arrangement of the suspension compo­nents that divides the loads into two sepa­rate paths has been developed and success­fully tested in a real vehicle. The decoupling from the static loads is realized by means of a serial arrangement of the actuator and a viscous damper.