Axis Calibration Method of Underwater Electric Field Measurement Sensor for Underwater Robot

This paper proposes a method to calibrate axis misalignment of underwater electric field sensors (EFS) for accurate electric signal measurements of underwater robots. An EFS measured a known electric field and the measured values were compared to their theoretical values to approximate the axis misalignment of the sensor. The approximation was optimized by using the Levenberg’s optimization algorithm. The optimization algorithm searched for the axis misalignment of the EFS that minimized the difference between the measured values and the theoretical values. After the optimization, the measurements with the EFS could be calibrated. The proposed method was tested in computer simulations. The results show that the proposed method could approximate the axis misalignment of the EFS and calibrate the measured electric fields. The calibration reduced the localization errors of an underwater robot when the robot electro localized its position by using electric field signals generated by an electric landmark. The proposed method would contribute to various applications that require accurate measurements of underwater electric signals, such as electro localization of underwater robots and detection of electric objects underwater.