Redesign of an auto-levelling base for submarine seismic sensor

Venice, Italy

The OBS (acronym of Ocean Bottom Seismometer) is a system to monitor the submarine
seismic activity. To properly work, an OBS system needs a suitable auto-levelling base to
maintain a fixed (horizontal) position during the measurement phases.
In this work a new auto-levelling base for submarine seismic sensors has been designed.
During the redesign process a preliminary phase of analysis of the state of art has been
made. Afterwards, the technological solutions chosen by different manufactures have been
critically analysed, and a full description of their functionalities, working principles and system
performances has been carried out. Later, some innovative concepts have been proposed.
Among these ones, the most interesting are the auto-levelling bases with spherical joint,
based on: air bearings, ball bearings and magnetic levitation systems.
The concept scoring method has been used to identify. as best concept, the auto-levelling
base with spherical joint and air bearings system.
Successively, the chosen concept has been implemented: the technical working principles
have been studied to choose the best solutions in terms of dimensions, shapes, materials of
all base components. A full parametric CAD model of the auto-levelling base has been also
created.
The new designed base, by using a very innovative auto-levelling system, allows to obtain
very good results as regards the accuracy of positioning, so ensuring a remarkable
improvement of the performances of the ocean bottom seismometers.

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