Fraunhofer Adaptronics Alliance
Distributed adaptive vibration absorbers
As a demonstration for the distributedvibration absorbers a segment of a 10m rescue boat was chosen. The aim is to reduce the structure-borne sound entry through the contact points of the internal combustion engine. The test structure shows an elastic behavior in the relevant frequency range. The excitation is provided by a multi-axis unbalance exciter. This iscapable to replicate the forces of the built-in 6-cylinder diesel engine in the dominant third engine order in the frequency range up to about 150 Hz.
The adaptive vibration absorbers are attached between the unbalance exciter and the boat segment. Via a control algorithm they can be tuned independently to the rotational frequency of the unbalance exciter. For this purpose the phase difference between the acceleration on the seismic mass and the connection point of the vibration absorber is determined. By a specific shift of the absorber masses using stepper motors the phase difference is set to 90°. As accelerometers low-cost MEMS sensors are used. The signal processing is performed on a dSPACE real-time system.