Dynamic Magnetometer Calibration and Alignment to Inertial Sensors by Kalman Filtering

摘要

Magnetometer and inertial sensors are widely used for orientation estimation.Magnetometer usage is often troublesome, as it is prone to be interfered byonboard or ambient magnetic disturbance. The onboard soft-iron materialdistorts not only the magnetic field, but the magnetometer sensor framecoordinate and the cross-sensor misalignment relative to inertial sensors. Itis desirable to conveniently put magnetic and inertial sensors information in acommon frame. Existing methods either split the problem into successiveintrinsic and cross-sensor calibrations, or rely on stationary accelerometermeasurements which is infeasible in dynamic conditions. This paper formulatesthe magnetometer calibration and alignment to inertial sensors as a stateestimation problem, and collectively solves the magnetometer intrinsic andcross-sensor calibrations, as well as the gyroscope bias estimation. Sufficientconditions are derived for the problem to be globally observable, even when noaccelerometer information is used at all. An extended Kalman filter is designedto implement the state estimation and comprehensive test data results show thesuperior performance of the proposed approach. It is immune to accelerationdisturbance and applicable potentially in any dynamic conditions.