Manoeuvring Simulations of Autonomous Underwater Vehicle using Quaternion

Abstract

The dynamics of an AUV, which can perform manoeuvres with pitch angles in the range of 90°is investigated in this paper. The purpose of the AUV is to perform a station-keeping manoeuvre at about 90°pitch angle by varying propeller revolution. The AUV is launched in horizontal orientation. Quaternion mathematics, 4 quadrant propeller open water characteristics, and PID controller for propeller revolution are incorporated in manoeuvring mathematical model for this purpose. A procedure for optimizing the gain coefficients for the PID controller is developed using the 7 DoF manoeuvring mathematical model. Two design configurations of the AUV are investigated, positively buoyant and negatively buoyant. The design objective is, the AUV shall travel as far away as possible from the parent vehicle using minimum energy and time. It is shown that both the optimal gain coefficients for the PID controller for propeller revolution and the dynamic response of the AUV is different for each design configuration. The methodology developed in the paper can be used in the design and propeller revolution control system for certain categories of AUVs. The study shows that prime mover torque/ shaft revolution and 7 DoF manoeuvring mathematical model are important in predicting the attitude and trajectory in space and station-keeping manoeuvring capability of an AUV launched from a parent vehicle.