Design and experimental evaluation of an integrated USBL/INS system for AUVs

This paper addresses the design, development, and test of an integrated Ultra Short Baseline (USBL) and Inertial Navigation System (INS) to be used as a low cost navigation system for underwater robotic vehicles. An architecture for the open prototype is proposed, the acoustic array design and calibration is discussed, the inertial sensors package is presented, supporting acoustic signals to be used are briefly enumerated, and implementation issues are detailed. The system includes also as a by-product the design of a transponder that replies to the interrogations sent out by the integrated USBL/INS system. Preliminary sea tests, conducted in an harbor, are presented to assess the feasibility of the acoustic positioning system, using namely Direct Sequence Spread Spectrum (DSSS) coded signals.