Abstract
Magnetometer calibration is a pre-processing step in the Attitude and Heading Reference Systems (AHRS) which has an essential role in many applications. The main purpose of this article is to derive an innovative and precise calibration approach for a magnetometer set installed on human body. To execute this calibration method, all the error parameters of multiple magnetometers are considered in an Unscented Kalman Filter (UKF) model for accurate estimation of calibration parameters. As achieving a precise estimation in Kalman filters-based algorithms needs an accurate and complete observation model, a special single-axis rotation trajectory for Inertial Measurement Unit (IMU) is performed to increase the observability rank of the calibration model. To evaluate the proposed method, five body-mounted sensors were experimented in the laboratory at the same time for applying in the body motion capture system. The results showed that all five sensors were well-calibrated without any need to be detached from the body and using any rotational robot arm. The resolution and precision of the proposed calibration method are assessed by the ellipsoid-fitting representation method. Consequently, all the body-mounted magnetometers were calibrated, on average, by about 1% uncertainty. The method can be used in every motion capture and AHRS applications due to its feasibility and simplicity.
Highlights
With prompt advancements in technology, the development of Microelectromechanical Systems (MEMS) has been under deep investigation of researchers and industries
The magnetic field can be considered as an important measurement in Kalman Filter (KF)-based AHRS [1, 2], Inertial Navigation Systems (INS), and motion capture models [3], some important attitude determination methods utilize the magnetometer as a compass to reduce the heading drift in Heuristic Drift Reduction (HDR)
It can be seen that the error parameters of calibration method are well estimated so, the calibrated data is located on the unit sphere with acceptable accuracy
Summary
With prompt advancements in technology, the development of Microelectromechanical Systems (MEMS) has been under deep investigation of researchers and industries. The integrated MEMS technology has had underlying impacts in various applications like Inertial Navigation Systems (INS), positioning and guidance, body motion capture, Attitude and Heading Reference Systems (AHRS), object tracking, etc. The magnetic field can be considered as an important measurement in Kalman Filter (KF)-based AHRS [1, 2], INS, and motion capture models [3], some important attitude determination methods utilize the magnetometer as a compass to reduce the heading drift in Heuristic Drift Reduction (HDR). The hard-iron effect is usually caused by the materials which generate a constant offset to each magnetometer axis.
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