Application of Linear Regulator to Dynamic Positioning System

Abstract

Dynamic positioning System (DPS) has been developed and operated for drilling rigs and work vessels in deep waters to keep position. In this paper the state feedback control based on multi-variable control system which takes the yaw-sway-suge coupling into account was compared with the conventional PID control system. Expressing the equation of motion in linear model, Linear Regulator Theory can be applied. Feedforward control is also effective in case the external forces can be mea-sured directly. Using the data of a typical drill ship, the computer simulations of state feedback control with feedforward were carried out comparing with that of PID control. From the results of simulation it was found that energy consumption of drill ships and lower-hull type semisubmersible rigs was remarkably reduced by state feedback control when the steady external forces like current exsist.