A method to align the coordinate system of accelerometers to the axes of a human body: The depitch algorithm

  • Authors:

  • Matthias Gietzelt;Stephan Schnabel;Klaus-Hendrik Wolf;Felix Büsching;Bianying Song;Stefan Rust;Michael Marschollek

  • Affiliations:

  • Peter L. Reichertz Institute for Medical Informatics, University of Braunschweig - Institute of Technology and Hannover Medical School, Mühlenpfordtstr. 23, D-38106 Braunschweig, Germany;Fraunhofer Institute for Surface Engineering and Thin Films, Department: Large Area Coatings, Bienroder Weg 54e, D-38108 Braunschweig, Germany;Peter L. Reichertz Institute for Medical Informatics, University of Braunschweig - Institute of Technology and Hannover Medical School, Mühlenpfordtstr. 23, D-38106 Braunschweig, Germany;Technische Universität Braunschweig, Institute of Operating Systems and Computer Networks, Mühlenpfordtstr. 23, D-38106 Braunschweig, Germany;Peter L. Reichertz Institute for Medical Informatics, University of Braunschweig - Institute of Technology and Hannover Medical School, Mühlenpfordtstr. 23, D-38106 Braunschweig, Germany;Peter L. Reichertz Institute for Medical Informatics, University of Braunschweig - Institute of Technology and Hannover Medical School, Mühlenpfordtstr. 23, D-38106 Braunschweig, Germany;Peter L. Reichertz Institute for Medical Informatics, University of Braunschweig - Institute of Technology and Hannover Medical School, Carl-Neuberg-Str. 1, D-30625 Hannover, Germany

  • Venue:
  • Computer Methods and Programs in Biomedicine
  • Year:
  • 2012

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Abstract

One of the key problems in accelerometry based gait analyses is that it may not be possible to attach an accelerometer to the lower trunk so that its axes are perfectly aligned to the axes of the subject. In this paper we will present an algorithm that was designed to virtually align the axes of the accelerometer to the axes of the subject during walking sections. This algorithm is based on a physically reasonable approach and built for measurements in unsupervised settings, where the test persons are applying the sensors by themselves. For evaluation purposes we conducted a study with 6 healthy subjects and measured their gait with a manually aligned and a skewed accelerometer attached to the subject's lower trunk. After applying the algorithm the intra-axis correlation of both sensors was on average 0.89+/-0.1 with a mean absolute error of 0.05g. We concluded that the algorithm was able to adjust the skewed sensor node virtually to the coordinate system of the subject.