Online Magnetometer Calibration in Consideration of Geomagnetic Anomalies Using Kalman Filters in Nanosatellites and Microsatellites

Magnetic sensors are reliable, lightweight, and low power consumption sensors that are utilized in almost all nanosatellites and microsatellites for a magnetic attitude control system using magnetic torquers (MTQs). In some nanosatellites and microsatellites, magnetic sensors are utilized for magnetic moment estimation to compensate for torques owing to magnetic dipole disturbances, which are the dominant disturbances in these small satellites. To estimate the magnetic moment accurately, the errors of the magnetic sensors caused by the magnetic anomaly and bias noise from electrical devices should be estimated and compensated precisely. Although several previous studies have focused on the estimation and compensation of the errors of the magnetic sensors, the magnetic anomaly of the geomagnetic field has not been considered, even though the anomaly introduces large estimation errors. This research proposes a method to estimate the time-variable errors arising from both magnetometer bias and the magnetic anomaly of the geomagnetic field using an extended Kalman filter (EKF) and unscented Kalman filter (UKF). Based on numerical simulation results, this study concludes that the effects of both magnetic sensor bias and magnetic anomalies can be compensated for by the proposed method.