Smart vibration damping improves comfort, reduces weight

March 13, 2014 // By Christoph Hammerschmidt
Vehicles without a solid roof construction such as roadsters and convertibles are inherently prone to torsional vibrations. To make the body more rigid and to reduce the vibrations, carmakers frequently use additional stiffenings along with passive vibration absorbers. Their disadvantage: They make the vehicle heavy. Fraunhofer LBF and company Trelleborg Vibracoustic - both entities based in Darmstadt, Germany - developed an intelligent active damper that does away with these drawbacks.

The active system saves weight and improves vibration behaviour at critical points such as steering wheel, driver's seat and A column. In addition, an adaptive control algorithm enables the vehicle to adjust itself to changing road and load conditions.

The "adaptronic" system devised by the Fraunhofer researchers and the Swedish engineers consists of an actuator, sensors, and a power amplifier with embedded signal processing. The actuator, an active vibration damper, had been developed before by Trelleborg Vibracoustics. In a first project step, the researchers analysed the vibration behaviour of a cabriolet on a test stand and measured the forces achievable by the actuators. The data acquired at the test stand then were used to create a numerical model that describes the vibration behaviour at various points. This model enabled the engineers to implement multiple model-based control algorithms for dampening the vibrations at key points in the vehicle such as seats, rear-view mirror or steering wheel and to evaluate them under the aspect of comfort.

As a conclusion, the Fraunhofer researchers say that in the context of integrating adaptronic systems increasingly embedded signal processing platforms obtain a crucial role. For this reason, they decided to further optimise the system by implementing the control algorithm on a powerful 32-bit microprocessor. The signal processing unit developed at Fraunhofer can be programmed through Matlab/Simulink. In a hardware-in-the-loop (HiL) test that describes the vehicle behaviour in real-time, the algorithm has been validated; during real-world driving trials it also has been verified.

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