Control of the Position of an Underwate Towed Robot

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1) A simulation program was developed of three-dimensional behavior of a long flexible cable under the influence of complex flow in the ocean, by which nonlinear behaviors can be accurately simulated. We confirmed a good agreement exists between computations and experiments.2) A theory for investigating the dynamic stability of a system composed of ship, long flexible cable, and underwater towed vehicle (robot) was developed. Under the assumption that the transverse deflection and tension are slowly varying along the cable, an equation of the vibration of cable was solved with WKB method, and the stability of a robot to the action of a control surface was investigated.3) We simulated the so-called statistical fluctuation due mainly to the internal waves in the ocean, and developed a simulation program in which an underwater robot is supposed to be guided to a specified position by maneuvering a towing ship. This simulation program involves all the results obtained in this project. Simulation results revealed that more advarfced ship control is necessary for a more accurate guidance of a robot, especially when the ocean flow is complicated.4) A theory of end-point control was investigated for the perfect guidance of a towed robot to a specified position, which can be used for the improvement in how to maneuver a towing ship.