Sy, LukeLukeSyRaitor, MichaelMichaelRaitorDel Rosario, MichaelMichaelDel RosarioRedmond, StephenStephenRedmondet al.2024-04-192024-04-192020 IEEE2021-04IEEE Transactions on Biomedical Engineeringhttp://hdl.handle.net/10197/25675Goal: This paper presents an algorithm for accurately estimating pelvis, thigh, and shank kinematics during walking using only three wearable inertial sensors. Methods: The algorithm makes novel use of a constrained Kalman filter (CKF). The algorithm iterates through the prediction (kinematic equation), measurement (pelvis position pseudo-measurements, zero velocity update, flat-floor assumption, and covariance limiter), and constraint update (formulation of hinged knee joints and ball-and-socket hip joints). Results: Evaluation of the algorithm using an optical motion capture-based sensor-to-segment calibration on nine participants (7 men and 2 women, weight 63.0±6.8 kg, height 1.70±0.06 m, age 24.6±3.9 years old), with no known gait or lower body biomechanical abnormalities, who walked within a 4×4 m 2 capture area shows that it can track motion relative to the mid-pelvis origin with mean position and orientation (no bias) root-mean-square error (RMSE) of 5.21±1.3 cm and 16.1±3.2∘ , respectively. The sagittal knee and hip joint angle RMSEs (no bias) were 10.0±2.9∘ and 9.9±3.2∘ , respectively, while the corresponding correlation coefficient (CC) values were 0.87±0.08 and 0.74±0.12 . Conclusion: The CKF-based algorithm was able to track the 3D pose of the pelvis, thigh, and shanks using only three inertial sensors worn on the pelvis and shanks. Significance: Due to the Kalman-filter-based algorithm's low computation cost and the relative convenience of using only three wearable sensors, gait parameters can be computed in real-time and remotely for long-term gait monitoring. Furthermore, the system can be used to inform real-time gait assistive devices.en© 2020 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.PelvisKinematicsBiomedical monitoringSensorsThree-dimensional displayAccelerationThighJournal Article6841293130410.1109/TBME.2020.30264642021-04-26https://creativecommons.org/licenses/by-nc-nd/3.0/ie/