An investigation of low noise reduction gear for the AUV "Urashima" and sea trial of its acoustic communication

An AUV goes along a pre-programmed route depending on the INS position; it is useful to watch the vehicle status and give commands correcting position error or alternating control mode by the existing state from a surface vessel in test phases. The AUV system has a digital acoustic communication system, capable of 4100 m maximum range in duplex. The communication range is shorter because the acoustic signal to noise ratio decreases at the AUV when a vertical thruster is operated. Noise is caused by reduction gear in the thruster unit. The reduction gear is improved to decrease the noise. The communication range is enhanced 2.5 times compared to previously, even if the thruster is operated in the sea. This article describes an investigation of low noise reduction gear for the acoustic down-link and test results.