System uses piezoceramics to dampen vibrations in cars

Engineers in Germany are hoping to reduce noisy vibrations in cars by using ‘smart materials’ that automatically change their shape.

A team from 11 of the Fraunhofer institutes is developing a system to dampen vibrations with piezoceramic electromechanical transducers that expand and contract as electric current is applied and removed.

The technology is designed to counter background noise generated from high-frequency (between 30 and 200Hz) vibrations in a car, rather than act as an additional suspension system softening bumps from uneven roads.

‘We want to decouple the chassis from the suspension,’ Dr Sven Herold, deputy head of the Fraunhofer Institute for Structural Durability and System Reliability LBF, told The Engineer.

‘The piezoceramics lie between them and are contracting and elongating in a way that the vibrations can be cancelled.

‘The vibration of the wheel is measured by acceleration sensors and processed in a control system that consists of adaptive control algorithms known as filters.’

The system was developed over the last three years in partnership with a consortium of eight industrial partners, including a car manufacturer.

So far, the team has tested a laboratory-scale demonstrator version of the technology but plans to fully integrate it into a working car and trial it using road simulations over the next six months.

The project is part of Fraunhofer’s ‘Adaptronics Alliance’, which is looking at a variety of ways of using so-called smart materials.

In a related project, researchers are using piezoceramics in the opposite way, developing components that convert the oscillations in a structure — such as a high-traffic bridge — to electrical energy.

This energy can be used to supply tiny sensors that can monitor the condition of the bridge and notify a control centre of any damage.

Another programme is studying magneto-rheological fluids, which solidify as a magnetic field is applied because they contain tiny particles that align to form fixed chains. These fluids are being used to develop a safety clutch for milling machines.

With the magnetic field activated, the substance creates a solid link between the drive shaft and cutter head. Removing the field by using an emergency shutoff returns the substance to a fluid state, breaking the connection to stop the machine.