  The VIRGO superattenuator (SA) is effective in depressing the seismic noise
below the thermal noise level above 4 Hz. On the other hand, the residual
mirror motion associated to the SA normal modes can saturate the dynamics of
the interferometer locking system. This motion is reduced implementing a
wideband (DC-5 Hz) multidimensional control (the so called inertial damping)
which makes use of both accelerometers and position sensors and of a DSP
system. Feedback forces are exerted by coil-magnet actuators on the top of the
inverted pendulum. The inertial damping is successful in reducing the mirror
motion within the requirements. The results are presented.
