AUV-SNUUV I을 위한 동적모델링과 유체동역학 계수 추정

Abstract

This paper describes the nonlinear mathematical modeling, hydrodynamic coefficients estimation, navigation and control simulation for a test bed autonomous underwater vehicle(AUV) named by SNUUV I(Seoul National University Underwater Vehicle I). The configuration of SNUUV I is a long cylinder of 0.25m in diameter and 1.35m in length with delta-type wings near its rear end. On each edge of the wings, a thruster of 1/4HP is mounted, which is used for both drive and turn as the output power is controlled. A pair of control surfaces installed near its front part generates pitching moments for vertical movement. The navigation system enables SNUUV I to estimate its absolute position and attitude in the local coordinates of towing tank in real time during controlled motion. The sensor system is composed of acoustic ranging sonars, pressure sensor, inclinometers, etc. Especially the heading angle and the relative distance from the tank wall are estimated by several ranging transducers in the towing tank where magnetic devices can not be used. A six degree of freedom mathematical model for SNUUV I is derived with linear and nonlinear hydrodynamic coefficients, which are estimated with the help of a potential code and also the system identification using multi-variable regression. Based on the mathematical model, a simulation program using a model based control algorithm is designed for heading control and wall following control of SNUUV I. It is demonstrated numerically that the navigation system together with controller guides the vehicle to follow the desired heading and path with a sufficient accuracy. This paper demonstrates that the model based control algorithm can be designed efficiently using the system identification based on vehicle motion experiments with a appropriate navigation system.