Objective This study proposes a design scheme for an underwater magnetic sensor calibration device. The device is composed of an electromagnetic coil and integrated navigation equipment which can be carried on a mobile platform to sail on the water surface, and realize the high-precision calibration of the position and attitude of the underwater magnetic sensor.
Methods According to information on the coil's attitude, orientation and trajectory, and the measured values of the magnetic field generated by the coil at the magnetic sensor, the position and attitude of the underwater magnetic sensor can be calculated using a nonlinear optimization algorithm. The mathematical model of the whole system is established and numerical verification tests are carried out, considering the effects of the measuring accuracy of the coil's position and attitude, the magnetic sensor's noise and measuring error, and geomagnetic interference.
Results When the device is used and the magnetic sensor is at a depth of 30 m underwater, the mean value of position error is not more than 0.06 m, and the mean value of attitude error is not more than 0.20°; the accuracy of the magnetic sensor itself is the main factor affecting the calibration accuracy.
Conclusions The proposed calibration device can achieve the high-precision calibration of the position and attitude of an underwater magnetic sensor at the same time, giving it great application value. It can be widely used in underwater magnetic target detection, resource exploration, medicine and other fields, especially scenarios involving the attitude deviation of underwater magnetic sensors.
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