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Sensors 2014, 14(11), 20008-20024; doi:10.3390/s141120008

Accurate Orientation Estimation Using AHRS under Conditions of Magnetic Distortion

Complex and Adaptive Systems Laboratory, School of Computer Science and Informatics, University College Dublin, Dublin 4, Ireland
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Received: 18 January 2014 / Revised: 16 September 2014 / Accepted: 17 September 2014 / Published: 24 October 2014
(This article belongs to the Section Physical Sensors)
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Abstract

Low cost, compact attitude heading reference systems (AHRS) are now being used to track human body movements in indoor environments by estimation of the 3D orientation of body segments. In many of these systems, heading estimation is achieved by monitoring the strength of the Earth’s magnetic field. However, the Earth’s magnetic field can be locally distorted due to the proximity of ferrous and/or magnetic objects. Herein, we propose a novel method for accurate 3D orientation estimation using an AHRS, comprised of an accelerometer, gyroscope and magnetometer, under conditions of magnetic field distortion. The system performs online detection and compensation for magnetic disturbances, due to, for example, the presence of ferrous objects. The magnetic distortions are detected by exploiting variations in magnetic dip angle, relative to the gravity vector, and in magnetic strength. We investigate and show the advantages of using both magnetic strength and magnetic dip angle for detecting the presence of magnetic distortions. The correction method is based on a particle filter, which performs the correction using an adaptive cost function and by adapting the variance during particle resampling, so as to place more emphasis on the results of dead reckoning of the gyroscope measurements and less on the magnetometer readings. The proposed method was tested in an indoor environment in the presence of various magnetic distortions and under various accelerations (up to 3 g). In the experiments, the proposed algorithm achieves <2° static peak-to-peak error and <5° dynamic peak-to-peak error, significantly outperforming previous methods. View Full-Text
Keywords: AHRS; particle filter; data fusion; inertial measurement units; magnetic distortion; motion capture AHRS; particle filter; data fusion; inertial measurement units; magnetic distortion; motion capture
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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Yadav, N.; Bleakley, C. Accurate Orientation Estimation Using AHRS under Conditions of Magnetic Distortion. Sensors 2014, 14, 20008-20024.

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