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

• Published in: Computer methods and programs in biomedicine Vol. 106; no. 2; pp. 97 - 103
• Main Authors: Gietzelt, Matthias, Schnabel, Stephan, Wolf, Klaus-Hendrik, Büsching, Felix, Song, Bianying, Rust, Stefan, Marschollek, Michael
• Format: Journal Article
• Language: English
• Published: Ireland Elsevier Ireland Ltd 01.05.2012
• Subjects: Acceleration; Accelerometer; Adult; Algorithms; Axes alignment; Coordinate system; Female; Gait; Gait analysis; Humans; Internal Medicine; Male; Models, Theoretical; Other; Reference Values; Accelerometer; Axes alignment; Coordinate system; Gait analysis
• ISSN: 0169-2607; 1872-7565
• DOI: 10.1016/j.cmpb.2011.10.014

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 0.05 g. We concluded that the algorithm was able to adjust the skewed sensor node virtually to the coordinate system of the subject.