title: Drift removal for improving the accuracy of gait parameters using wearable sensor systems.
abstract: Accumulated signal noise will cause the integrated values to drift from the true value when measuring orientation angles of wearable sensors. This work proposes a novel method to reduce the effect of this drift to accurately measure human gait using wearable sensors. Firstly, an infinite impulse response (IIR) digital 4th order Butterworth filter was implemented to remove the noise from the raw gyro sensor data. Secondly, the mode value of the static state gyro sensor data was subtracted from the measured data to remove offset values. Thirdly, a robust double derivative and integration method was introduced to remove any remaining drift error from the data. Lastly, sensor attachment errors were minimized by establishing the gravitational acceleration vector from the acceleration data at standing upright and sitting posture. These improvements proposed allowed for removing the drift effect, and showed an average of 2.1°, 33.3°, 15.6° difference for the hip knee and ankle joint flexion/extension angle, when compared to without implementation. Kinematic and spatio-temporal gait parameters were also calculated from the heel-contact and toe-off timing of the foot. The data provided in this work showed potential of using wearable sensors in clinical evaluation of patients with gait-related diseases.
authors.affiliation: Division of Human Mechanical Systems and Design, Faculty of Engineering, Hokkaido University, Sapporo 060-8628, Japan. r.takeda@eng.hokudai.ac.jp.
authors.forename: Ryo
authors.initials: R
authors.lastname: Takeda
authors.affiliation: Department of Mechanical and Aerospace Engineering, Politecnico di Torino, Torino 10129, Italy. giulia.lisco@polito.it.
authors.forename: Giulia
authors.initials: G
authors.lastname: Lisco
authors.affiliation: Division of Human Mechanical Systems and Design, Graduate School of Engineering, Hokkaido University, Sapporo 060-8628, Japan. tadashi-fujisawa@ec.hokudai.ac.jp.
authors.forename: Tadashi
authors.initials: T
authors.lastname: Fujisawa
authors.affiliation: Department of Mechanical and Aerospace Engineering, Politecnico di Torino, Torino 10129, Italy. laura.gastaldi@polito.it.
authors.forename: Laura
authors.initials: L
authors.lastname: Gastaldi
authors.affiliation: Department of Health Science, Hokkaido University School of Medicine, Sapporo 060-0812, Japan. tohyama@med.hokudai.ac.jp.
authors.forename: Harukazu
authors.initials: H
authors.lastname: Tohyama
authors.affiliation: Division of Human Mechanical Systems and Design, Faculty of Engineering, Hokkaido University, Sapporo 060-8628, Japan. tadano@eng.hokudai.ac.jp.
authors.forename: Shigeru
authors.initials: S
authors.lastname: Tadano
mesh_terms: D056044:Actigraphy / Q000295:instrumentation* / Q000379:methods; D000465:Algorithms; D016477:Artifacts; D004867:Equipment Design; D019544:Equipment Failure Analysis; D005684:Gait / Q000502:physiology*; D006801:Humans; D007866:Leg / Q000502:physiology; D018670:Monitoring, Ambulatory / Q000295:instrumentation* / Q000379:methods; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012815:Signal Processing, Computer-Assisted; D059629:Signal-To-Noise Ratio; D014159:Transducers