title: An IMU-to-Body Alignment Method Applied to Human Gait Analysis.
abstract: This paper presents a novel calibration procedure as a simple, yet powerful, method to place and align inertial sensors with body segments. The calibration can be easily replicated without the need of any additional tools. The proposed method is validated in three different applications: a computer mathematical simulation; a simplified joint composed of two semi-spheres interconnected by a universal goniometer; and a real gait test with five able-bodied subjects. Simulation results demonstrate that, after the calibration method is applied, the joint angles are correctly measured independently of previous sensor placement on the joint, thus validating the proposed procedure. In the cases of a simplified joint and a real gait test with human volunteers, the method also performs correctly, although secondary plane errors appear when compared with the simulation results. We believe that such errors are caused by limitations of the current inertial measurement unit (IMU) technology and fusion algorithms. In conclusion, the presented calibration procedure is an interesting option to solve the alignment problem when using IMUs for gait analysis.
authors.affiliation: Postgraduate Program in Electrical Engineering, Federal University of Espirito Santo (UFES), 29075-910 Vitória-ES, Brazil. laura.valencia@aluno.ufes.br.
authors.forename: Laura Susana
authors.initials: LS
authors.lastname: Vargas-Valencia
authors.affiliation: Postgraduate Program in Biotechnology, Federal University of Espirito Santo (UFES), 29040-090 Vitória-ES, Brazil. arlindo.elias@aluno.ufes.br.
authors.forename: Arlindo
authors.initials: A
authors.lastname: Elias
authors.affiliation: Postgraduate Program in Electrical Engineering, Federal University of Espirito Santo (UFES), 29075-910 Vitória-ES, Brazil. e.rocon@csic.es.|Neural and Cognitive Engineering Group, Centro de Automática y Robótica, CSIC-UPM, 28500 Madrid, Spain. e.rocon@csic.es.
authors.forename: Eduardo
authors.initials: E
authors.lastname: Rocon
authors.affiliation: Postgraduate Program in Electrical Engineering, Federal University of Espirito Santo (UFES), 29075-910 Vitória-ES, Brazil. teodiano.bastos@ufes.br.
authors.forename: Teodiano
authors.initials: T
authors.lastname: Bastos-Filho
authors.affiliation: Postgraduate Program in Electrical Engineering, Federal University of Espirito Santo (UFES), 29075-910 Vitória-ES, Brazil. frizera@ieee.org.
authors.forename: Anselmo
authors.initials: A
authors.lastname: Frizera
mesh_terms: D000465:Algorithms; D053587:Arthrometry, Articular; D001696:Biomechanical Phenomena; D002138:Calibration; D003198:Computer Simulation; D005684:Gait / Q000502:physiology*; D006801:Humans; D007596:Joints / Q000502:physiology; D007866:Leg / Q000502:physiology; D010827:Physiology / Q000379:methods*; D015203:Reproducibility of Results; D012399:Rotation
keywords: anatomical calibration; human motion analysis; inertial sensor; joint angular kinematics; technical frames