A robust dynamic positioning control algorithm and its validation through experiment and numerical simulation

Abstract

A robust control algorithm for dynamic positioning (hereinafter DP) is discussed in this paper. For validation of a robust control algorithm, a shuttle tanker which has six thrusters is considered as dynamic positioned vessel. The thruster system consists of three tunnel thrusters, two azimuth thrusters and one main propeller with rudder. It is also assumed that each thruster has limitation in generation of thrust in accordance with commercial thruster system. Conventional proportional and derivative (hereinafter PD) control algorithm is implemented for main feedback controller. A modified Integral (mod-I) controller is also applied in DP system to suppress steady state error. To allocate thrust, well known minimum power consumption algorithm based on Lagrange multiplier method is used. In the thrust allocation algorithm rudder effect in main propulsion system is considered. An extended Kalman filter (EKF) is used to separate low frequency (hereinafter LF) motion from total motion of the vessel. A set of experiment is designed and conducted to validate the present DP control algorithm. Experimental and numerical results for DP performance of a shuttle tanker are compared in this paper while in the numerical analysis the same control methodologies with experiment are implemented. Copyright ？ 2013 by the International Society of Offshore and Polar Engineers (ISOPE).