Design of underwater robots for live exhibition in a museum of marine science and technology

Abstract

This talk addresses two different designs of underwater robots: a bay monitoring flatfish type autonomous underwater vehicle (AUV), and a fleet of robotic fish that swims in an exhibition tank. Both of them are for the live demonstration of underwater robotics technology in a museum of marine science and technology in Keelung, Taiwan.Hydrodynamic maneuverability data of the AUV will be presented. The data comprise added mass and inertia coefficients, damping, lift and drag coefficients of the vehicle and its control surfaces, as well as resistance and propulsion characteristics. The hydrodynamic data have been determined by full scale tests, using a towing tank equipped with a Planar Motion Mechanism. Free-sailing tests have been carried out as well. The AUV has an overall length of 2.5 m and is driven by two propellers, four vertical and two horizontal thrusters (Fig. 1). The AUV performs seabed inspection using HD camera and environmental surveys in the bay area (Fig. 2) in front of the museum.Robotic fish (Fig. 3) that swims in an exhibition tank must detect the position of walls and avoid obstacles. Both sides of a robotic fish are distributed by PVDF sensors which can sense the variances of the surrounding flow field. An image source method is employed to deal with the reflected acoustic wave from the wall, which is propagated from the oscillating tail fin. Then the sensors will measure the pressure variations and by using an extended Kalman filter to decrease the uncertainty in the data measurement and increase the stability of the robotic fish, while it is moving forward near a wall. Visitor detection and tracking are performed by integrating several sensory systems around the exhibition pool. We designed an underwater communication system which is based on wireless optical communication method. Visitors' states such as motion trajectories, sounds are transferred to the robotic fish in the tank through the one-way communication link. Interactions between the audience and the robotic fish are achieved for the robotic fish by approaching visitors autonomously and displaying certain action scenarios.