Active isolation of ship machinery platforms

The major pieces of machinery on board a ship tend to be mounted on a common platform, which is flexibly mounted on the hull, in order to isolate the machinery vibration from the ship structure and to facilitate their relative alignment. The author describes the use of active control to reduce the level of excitation of the platform structure, subject to a forcing function with a known spatial and temporal distribution. This is achieved in two stages: first, by modifying the dynamics of the platform structure, i.e. its mode shapes and natural frequencies; and second, by introducing damping into these modes. It is assumed that the damping introduced does significantly modify the mode shapes