Basic Research on Monitoring System of Environment in Coastal Waters by Autonomous Underwater Robots

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This research has been carried out to establish 1) guidance and control system of autonomous underwater vehicles (AUVs) in coastal waters and 2) design of configuration of AUVs in coastal waters for the purpose of development of global monitoring system of environment in coastal area by AUVs. This research deals with an autonomous underwater vehicle equipped with mechanical pectoral fins that has a high performance of attitude control under disturbances like water currents and surface waves in coastal waves.In the first year of this program, the optimization of the fin motion in terms of optimal control force generation was carried out using a mechanical fin system generating flapping motion, feathering motion and rowing motion. Kinematic studies indicate that pectoral fin motion of fish consists of drag-based mode at low speed and lift-based mode at high speed. The optimization found out that the lift-based rather than the drag-based swimming mode is suitable for generation of propuls … More ive force in uniform flow, while the drag-based rather than the lift-based swimming mode is suitable for generation of propulsive force in still water.In the second year of this program, the underwater vehicle equipped with two pairs of mechanical pectoral fins "PLATYPUS" was developed to assess the swimming performance and the control performance. We found that it has not only quite a good propulsive performance, showing the maximum speed of 0.64 m/s with lift-based swimming mode, but also a variety of maneuverability in hovering condition such as turning, descending and ascending, and lateral swimming. The task sharing by fore and aft pairs of mechanical pectoral fins enables a precise Point To Point control in 3-D underwater space that needs simultaneous performance of azimuth control, position control in horizontal plane and depth control. The drag-based swimming mode of the mechanical pectoral fin rather than the lift-based swimming mode is suitable for the motion control of the underwater vehicle that needs a prompt response under disturbances such as waves. Less