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Self-excited vibrations are observed in many technical applications. Frictional contacts are often involved in the mechanism which generates vibrations. Reasons for the excitation mechanisms are decreasing friction characteristics depending on the sliding velocity, fluctuating normal loads or different geometrical effects. First, the mechanisms are explained using simple examples. The practical relevance of self-excited, frictioninduced vibrations is exemplified with three technical systems: a system with an axial seal; a tread block of a tyre; and a disc brake.The knowledge of the excitation mechanism is necessary to introduce successfully design countermeasures. These measures to avoid self-excited vibrations are important to solve practical problems. They are the main focus of this work. Further, additional passive and active subsystems are described and validated experimentally. Therefore, a large range of design, active and passive solutions are given.

Piezoelectric shunt damping with mechanical structures has been an active research topic for several years. Standard passive techniques suffer from a very limited and frequency-dependent damping performance. Recently, semi-active switching techniques-namely SSDI (synchronized switch damping on inductor) and SSDV (synchronized switch damping on voltage source) techniques-have been proposed, which are capable of adapting to variations of the excitation frequency without reduction in performance. Crucial for the damping performance is the tuning of the shunt parameters and the precise switching sequence.In this paper, an analytical analysis of the switching technique is presented, which includes the influence of all shunt parameters and the switching times. New results concerning the optimal tuning of the inductance and the switching sequence are obtained, and it is shown that the enhanced SSDV technique can be equated with the SSDI technique, albeit with an increased effective piezoelectric force factor. Measurements are conducted to validate the theoretical results.

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