Bilateral Step Length Estimation Using a Single Inertial Measurement Unit Attached to the PelvisBy Koese, Alper; Cereatti, Andrea; Della Croce, Ugo ; Journal of NeuroEngineering and Rehabilitation, Volume 9, Number 9
Publication Date: February 8, 2012
Paper presents a method for estimating step length bilaterally, during level walking, using a single inertial measurement unit (IMU). The method was developed as the measurement of temporal and spatial features of gait is essential for the assessment of gait abnormalities and the quantitative evaluation of treatment outcomes. The IMU used was FreeSense, featuring a tri-axial accelerometer and two bi-axial gyroscopes sampling data at 100 frames per second. The method was validated using measurements from a stereo-programmetic (SP) system as a gold standard on 9 healthy participants walking 10 laps at varying speeds along a closed loop track of about 25 meters. The IMU was placed at pelvis level fixed to participants’ belt on the right side. For each loop, only the IMU data recorded in a 4 meter long portion of the track included in the calibrated volume of the SP system were used for the analysis. The method takes advantage of the cyclic nature of gait and requires an accurate determination of the foot contact instances. A combination of a Kalman filter and an optimally filtered direct and reverse integration applied to the IMU signals formed a single novel method: the Kalman and Optimally filtered Step length Estimation (KOSE) method. A correction of the IMU displacement due to the pelvic rotation occurring in gait was implemented to estimate the step length and the traversed distance. The step length was estimated for all participants with less than 3 percent error. Traversed distance was assessed with less than 2 percent error.
Published by: BioMed Central Ltd (Website:http://www.biomedcentral.com)
Link to text: http://www.jneuroengrehab.com/content/pdf/1743-0003-9-9.pdf