Ocean scientists are beginning to employ unmanned robotic vehicles to conduct surveys in oceans, lakes, and estuaries. The goal of these surveys is to provide a better understanding of underwater biology, ecology, geology, physical oceanography, and the interaction of air, sea, and ice worldwide. These data improve scientists' understanding of global ecology and climate that are of great societal importance. Having the ability to conduct precision near-bottom oceanographic surveys with unmanned underwater vehicles (UUVs) is unprecedented, yet the widespread use of precision navigation techniques on UUVs is limited by the high cost of true-North attitude sensors. This project seeks to develop a high-accuracy comparatively low-cost, compact, and low-power true-North seeking attitude (heading, pitch, and roll) sensor, and to incorporate this new instrument into a tightly integrated precision Doppler navigation system for UUVs. The goal is to develop a comparatively low-cost and high-accuracy navigation system to enable small low-cost UUVs to perform science missions requiring high-precision navigation (e.g. high precision hydrographic survey, time-series acoustic and optical survey for environmental assessment) that are presently considered impractical or infeasible with low-cost UUVs. This project will enable hands-on research by undergraduate and graduate students and dissemination of their research results. The instrument design will be made open-source, including mechanical designs, and electrical designs, and software algorithms that will be freely available as open-source software packages.
This project has three technical goals: First, employ the new class of relatively low-cost commercially-available-off-the-shelf (COTS) inertial measurement units (IMUs) equipped with integrated 3-axis fiber-optic gyro (FOG) angular-rate sensors and 3-axis micro-electromechanical systems (MEMS) accelerometers, together with real-time state estimation methods to provide accurate estimation of the heading, pitch, and roll of the instrument relative to true-North and the local gravity field. Second, develop improved underwater navigation methods employing low-cost FOG IMUs and bottom-lock Doppler sonars. Third, evaluate these navigation methods in full-scale experimental trials with UUVs in a test-tank and at sea.
