Redesign of an auto-levelling base for submarine seismic sensor

Abstract

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.