Onboard estimation and correction of magnetometer bias in MEMS based Tri axial Inertial Measurement Unit

Abstract

MEMS based tri axial Inertial Measurement Unit (IMU) are used in nano/pico satellites for attitude determination and control. For magnetically controlled satellites tri axial magnetometer data of Inertial Measurement Unit (IMU), is used to derive the three axis attitude onboard. But the accuracy of the magnetometer may be compromised by large systematic magnetic disturbances on the satellite. Even the magnetic fields due to onboard electronics leads to residual magnetic fields which adds as bias in the measured magnetic field data. This paper describes the onboard estimation and correction of magnetometer bias using state estimator. The attitude independent state estimator is derived to ensure bias estimation even at high attitude errors. The algorithm has been implemented onboard for a nano satellite with active magnetic control system named PISAT.