Abstract
ABSTRACT This paper presents the designs of two observers, which are: the extended Kalman filter and the nonlinear passive observer. Based on the measured values of ship position and heading, the observers estimate the surge, sway and yaw velocities of the ship motion. The observers make use of the simplified nonlinear mathematical model of ship motion in which the neglected ship dynamics and disturbances are modelled using bias. The designed observers firstly have been simulated on a computer model where their parameters were calibrated, and then were implemented on the physical model of the training ship “Blue Lady” in the ship handling centre in Ilawa-Kamionka. The comparative analysis was done with respect to the estimated variables describing the ship motion in three directions: surge, sway and yaw
Highlights
Dynamic positioning is the control system which automatically keeps the ship position and heading using propellers and thrusters installed on the ship
The here presented nonlinear observer is similar to that proposed by Fossen and Strand and used in the dynamic positioning system (Fossen and Strand, 1999)
The simulation tests were performed in the calculating environment Matlab/Simulink based on the mathematical model of Blue Lady described in detail by Gierusz [21, 22]
Summary
Dynamic positioning is the control system which automatically keeps the ship position and heading using propellers and thrusters installed on the ship. The improved version of this design was presented by these same authors [10] Those works are considered the first cases in which a fully nonlinear system of dynamic positioning was used - this system missed wave filtration, and bias modelling and estimation to separate the non-modelled slowly changing disturbances. Hajivand and Mousavizadegan have designed a nonlinear observer for wave filtering and velocity estimation Their observer makes use of the memory effect and takes into account the dependence of the added mass and damping coefficient changes in the ship dynamics model on the oscillatory forces acting on the ship hull [16]
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