It has been commonly assumed that the corner or mount frequency in an
isolator should be designed as low as possible. This is one result of
using a single-degree-of-freedom (SDOF) system to model isolation syst
ems. However, for systems that have flexible or non-rigid foundations,
a design point for the mount frequency can occur between the modes of
the base. By implementing this type of design, a strong interaction w
ill exist between the modes. When isolator damping is included, whethe
r done passively or actively, more than one mode can be attenuated by
this new mount design. Therefore, the effects of the mount frequency o
n isolation designs are discussed as well as using both passive and ac
tive damping in the isolator. For active damping, three commonly used
control methodologies are discussed: a proportional-plus-integral-plus
-derivative (PID) controller, a linear quadratic Gaussian (LQG) regula
tor and a positive position feedback (PPF) controller. (C) 1998 Academ
ic Press.