THETIS: an underwater remotely operated vehicle

In this paper the under development THETIS ROV is described. The control, communication and positioning subsystems are presented. The communication system comprises a twin fiber optic cable for two way communications, a special communication protocol and a transfer speed up to 115.2 Kbps. The on board slave computer collects through A/D and the appropriate sensors environmental data. Furthermore the slave computer controls the vehicle's six DOF motion through its D/A interface cards. The thrusters are DC motors and are controlled using PWM technique. The control methods tested include classical and modern approaches. An ultrasonic positioning system used to maintain a fixed position in space as well as the camera based vision system are described.