Using genetic algorithms for compensating the local magnetic perturbation of a ship in the earth's magnetic field

This paper shows a practical application of genetic algo- rithms (GAs) for compensating the local magnetic perturbation produced by a ship, while moving in the earth's magnetic field. The compensation is achieved by modifying the number of turns and the current magnitude across the so-called degaussing coils distributed along the ship. A GA scheme for automatic optimisation of these parameters is used. A new objective-function strategy, called a boundary method, is proposed. It is shown that the convergence of the GA is greatly improved when the new objective function is used. Different selection mechanisms, objective function strategies, and scaled methods are revised in this paper. The results show that GAs can be efficiently used to reduce drastically the magnetic field levels of real practical ships