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The advent of quieter-running machines

Adaptronics is seen as one of the key technologies of the 21st century. Now that the fundamental research has been done, Fraunhofer researchers are ready to tackle real-life projects.

At the joint Fraunhofer stand devoted to Adaptronics (D24/1) in Hall 2 of the Hannover Messe (April 16 to 20), they will be presenting the Quiet Car project, which demonstrates to the industrial world what adaptronic systems are capable of achieving. It’s every driver’s nightmare – a tire burst when you’re traveling at maximum speed along the freeway. In theory, any car owner can reckon on having to change a burst tire after driving between 100,000 and 150,000 kilometers. This explains why the leading auto magazines and tire manufacturers recommend twice-monthly tire checks. So-called run-flat tires are a safer option, for they serve as a normal tire and spare tire rolled into one. They allow the driver to continue driving for a certain distance with a burst tire, thanks to an additional rubber lining that prevents the damaged tire from totally deflating. Run-flat tires have been available on the market since 2001, but they have been slow to attract customers because they are more expensive than standard tires and also generate more noise. This is where the adaptronics solutions developed by Fraunhofer researchers could provide help, for instance by reducing the noise level inside the vehicle by actively damping the propagation of vibration-induced noise. “In a factory, noise is generated by the metal cladding of the machines, machine tools generate vibrations, and power generators and motors use oscillating frequencies that create a noise disturbance for workers and interfere with other equipment: there is a direct correlation between technological progress, lightweight construction, vibration, reliability and noise,” explains Tobias Melz of the Fraunhofer Institute for Structural Durability and System Reliability LBF in Darmstadt, who also manages the business activities of the Fraunhofer Adaptronics Alliance. “Active adaptronic structures help to reduce the vibrations caused by machines and vehicles – and hence the noise they produce. Manufacturers of run-flat tires are not the only ones to benefit from the advantages of adaptronics. Manufacturing processes can be run more efficiently when the machines operate with greater precision. This opens up a whole range of new possibilities, especially for components and products used in lightweight construction. In general terms, adaptronics is capable of furnishing more comfort, functionality and safety in all areas of engineering.” In the Fraunhofer Adaptronics Alliance, project teams from different Fraunhofer Institutes are developing solutions for mechanical structures, covering all stages of the engineering process, from materials science to system reliability. “Our project results are improving all the time in terms of quality, speed and costs, and we have now reached the stage of working on pre-production manufacturing processes,” reports Professor Holger Hanselka, director of the LBF and spokesman for the Alliance. The researchers’ method of reducing vibrations involves combining sensor and actuator functions with electronic feedback control circuits. The sensors and actuators are designed to respond in a defined way to parametric changes in their operating environment. An object’s mechanical properties, such as damping capacity or stiffness, can be synthetically modified by software. This makes it possible to reduce vibration, cut down noise, or even regulate the shape of certain components. This capacity of adaptronic devices to adapt in a defined way to their environment sometimes earns them the label of being “intelligent”. In the Quiet Car project, two adaptronics solutions have been integrated in a compact-class car. The researchers have equipped a Volkswagen Lupo with four active mounting units in the rear part of the chassis, and are testing its road behavior. At the same time, they are elaborating an active damping mechanism for the “firewall” that separates the passenger and engine compartments. Later this spring, the vehicle will undergo trials on a test circuit operated by the Fraunhofer LBF and Technische Universität Darmstadt at the disused airfield in Griesheim. The research objective of the Quiet Car project is to answer questions related to system integration in a complex engineering context. It also provides an opportunity for the engineers to publicize the new technology, given that they are obliged to keep much of their everyday research and development work under strict confidentiality.

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