Motion Simulation of an Underwater Vehicle with Mechanical Pectoral Fins Using a CFD-based Motion Simulator

The inspection of coastal and offshore structures is important for their life cycle assessment. We have been developing an underwater vehicle equipped with two pairs of mechanical pectoral fins for this mission. If underwater vehicles are used as an automatic inspection system, the determination of the desired levels of guidance and control law for the underwater vehicle is essential. However, since the inflow velocity to the fins is under the influence of the wake generated by the body, numerical methods must be used to predict hydrodynamic force generated by the fins. Therefore, we began working on a project for developing a numerical motion simulator for the underwater vehicle equipped with mechanical pectoral fins. We had already developed a CFD-based motion simulator. However the computational results were fairly different from the measured data. Therefore, we tried to improve this motion simulator from the viewpoint of hydrodynamic drag of the fuselage of the underwater vehicle. Using the improved motion simulator, the computation of the motion of the underwater vehicle with simple fin motion is carried out. As the result, the computed data shows good agreement with the measured one. The motion control simulation with Fuzzy control algorithm is also carried out. It is confirmed using the motion control simulator works well.