Audi's new magnetic semi-active suspension system

June 18, 2006 The Audi TT is a cult car, an icon –from the day it made its debut, in autumn 1998, it took the sports coupe segment by storm, sharpening the brand's profile in the process. We reported on the coming of the second generation of this successful model in April but overlooked one of the most interesting facets of the new machine which uses a completely new form of damping technology developed in conjunction with Delphi that resolves the age-old conflict between comfort and driving dynamics without countenancing any of the otherwise unavoidable compromises. As a continuously adaptive system, it adapts the damping characteristic to the profile of the road and the driver's gear-shifting habits within just a few milliseconds. The shock absorber pistons on the TT do not contain conventional oil, but a magneto-rheological fluid – a synthetic hydrocarbon oil in which microscopically small magnetic particles measuring between three and ten microns are enclosed. When a voltage is applied to a coil – by means of a pulse delivered by a control unit – a magnetic field is created in which the alignment of the particles changes. They position themselves transversely to the direction of flow of the oil, and so inhibit its flow through the piston channels. This alters the characteristic of the damping characteristic much faster than is the case in conventional adaptive dampers.

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