Research On The Magnetic Compass Correction System Of Ship

The deviation of magnetic compass was influenced by the modern ships mightily, which might appear fourty or fifty degrees, even the compass deviation completely weaken pointing north, or making it lose the capability of pointing northnavigate. Therefore, the international sail ARATS made the provision, The magnetic compass of the ship was measureing and correcting of compass under the conditions as follows: fixing, moving, changing the nearby buildings, taking place a violent vibration, ship body through electric welding, ship fixing at a direction anchor more than a month, ship transporting a great deal of magnetism goods, didn't remove compass deviation with the soft iron after responding from it but sail latitude changed over ten degrees, and so on. Meanwhile, because the tradition method from compass correction needed cost a great deal of manpower, material resources and financial power, some new methods of compass correction were pursued by producers.Correct system of magnetic compass was an intelligence device under a simple condition, which was a new technic combinating the gyrocompassive technique and the magnetic compass. This system made use of auto measurement technique of electricity compass to turn numeral direction signal, design numeral direction system, make use of the originally system acquire the true value; Using magnetoresistive sensor to induct the environment magnetic field for compass course, the magnetic singal of course was numerical, the magnetic compass deviation automatic measurement and correction system synthesizes both gyrocompass and magnetic compass technique.This system utilized magnetoresistive sensor to induct the environment magnetic field for compass course, and got true course from gyrocompass, then compared compass course with true course in order to compute compass deviation. Its principle was that: the magnetoresistive sensor inducted the outside magnetic field, gived out the compass course signal to A/D and then the signal was transformed into digital signal, processed by SCM ,thus we might get the compass course; through the process of synchronous motror or stepping motor, we compared the change of signals, used the gyrocompass numerical course calculated by SCM as the real time true course; we then compasred the numerical and real time true course (gyrocompass numerical compass), to get the compass deviation, and subtract gyrocompass course to get the deviation; through the calculation of SCM, we got five deviation coefficients and calculate the deviation each course in order to make SCM to correct the compass calculate the deviation each course in order to make SCM to correct the compass deviation software gyrocompass. Through a series of research, expersistive sensor was less than 0.5°,and after the measurement and correction of compass deviation through gyrocompass,thd signal error emitted by magnetoresistive magnetic compass is about l°.This system may also remove the influence on ship deviation caused by ship inclining,showing the real time compass course,magnetic course and true course meanwhile this paper also make a comparison with other magnetic compass technique and the corresponding ways of measuring and correcting,thus reach a conclusion that gyrocompass comparison way of measuring deviation is specially appropriate for the deviation measureent and correction of those large or medium_size ships.