In recent years, predictions of changes in the environment on earth and studies on ecodevelopment have become important. For this research on going ocean data in time and space is required, and has been obtainable using by mooring systems. However, a conventional mooring system can observe only discrete data in perpendicular space and moreover, construction of such a system requires a manpower and great expense. To solve this problem, an underwater vehicle for virtual mooring has been developed at Research Institute for Applied Mechanics (RIAM). The vehicle glides back and forth between the sea surface and the seabed collecting ocean data, with direction control regulating the vehicle's position in a designated area. This paper describes the testbed vehicle "LUNA" that was designed to develop a virtual mooring system, and the control algorithm is discussed.
The concept of virtual mooring using an underwater vehicle is shown in Fig.1. The vehicle that houses various observation equipment dives to the seabed where it carries out virtual mooring. When the vehicle returns to the sea surface, the measured data is transmitted to a research base through an artificial satellite. The vehicle then automatically checks its current position by GPS. If the position is out from the virtual mooring ocean space because of currents etc., the vehicle is controlled and again dives to return the previous area. The vehicle repeats diving and surfacing periodically. On the seabed, the vehicle rests during the set period and power supplies other than control equipment are shut off. The gliding ratio and the course of the vehicle are controlled by moving the position of the built-in weight (see Fig.27, Fig.29 and Fig.31). The depth of the vehicle is controlled by buoyancy adjustment equipment (see Fig.27, Fig.28 and Fig.31).
