With progress in technology, the problem of protecting human-beings, ma-
chines and technological processes from !>Ources of vibration and
impact has become of utmost importance. Traditional "classical" methods
of pro- tection, based upon utilising elastic passive and dissipative
elements, turn out to be inefficient in many situations and can not
completely satisfy the complex and often contradictory claims imposed on
modern vibration protection systems which must provide high performance
at minimum di- mensions. For these reasons, active vibration protection
systems, which are actually systems of automatic control with
independent power sources, are widely used nowadays. Appearing and
developing active systems require that traditional ap- proaches to the
analysis and synthesis of vibration protection systems must be revised.
Firstly, there exists the necessity to re-state the problem of vi-
bration protection from mechanical actions as an equivalent problem in
closed-loop control systems design, which is to be solved by the methods
of control theory. Furthermore, it turns out that certain inherent
proper- ties of active systems must be taken into account for a proper
design. In the majority of cases, the dynamic models of the objects to
be protected and the bases to which these objects are to be attached
must be revised. They are no longer considered as rigid bodies but
elastic bodies with weak dissipation.