Department of Mechanical Engineering, University of Alberta, Donadeo Innovation Centre for Engineering, Edmonton, Alberta T6G 1H9, Canada.
Department of Mechanical Engineering, University of Alberta, Donadeo Innovation Centre for Engineering, Edmonton, Alberta T6G 1H9, Canada.
J Biomech. 2019 Mar 6;85:224-229. doi: 10.1016/j.jbiomech.2019.01.027. Epub 2019 Jan 21.
Magnetic and Inertial measurement units (MIMUs) have become exceedingly popular for ambulatory human motion analysis during the past two decades. However, measuring anatomically meaningful segment and joint kinematics requires virtual alignment of the MIMU frame with the anatomical frame of its corresponding segment. Therefore, this paper presents a simple calibration procedure, based on MIMU readouts, to align the inertial frame of the MIMU with the anatomical frames, as recommended by ISB. The proposed calibration includes five seconds of quiet standing in a neutral posture followed by ten consecutive hip flexions/extensions. This procedure will independently calibrate MIMUs attached to the pelvis, thigh, shank, and foot. The accuracy and repeatability of the calibration procedure and the 3D joint angle estimation were validated against the gold standard motion capture system by an experimental study with ten able-bodied participants. The procedure showed high test-retest repeatability in aligning the MIMU frame with its corresponding anatomical frame, i.e., the helical angle between the MIMU and anatomical frames did not significantly differ between the test and retest sessions (except for thigh MIMU). Compared to previously introduced procedures, this procedure attained the highest inter-participant repeatability (inter-participant coefficient of variations of the helical angle: 20.5-42.2%). Further, the proposed calibration would reduce the offset errors of the 3D joint angle estimation (up to 12.8 degrees on average) compared to joint angle estimation without calibration (up to 26.3 degrees on average). The proposed calibration enables MIMU to measure clinically meaningful gait kinematics.
在过去的二十年中，磁性和惯性测量单元（MIMU）已成为人体运动分析的常用工具。然而，要测量具有解剖学意义的节段和关节运动，需要将 MIMU 框架与相应节段的解剖框架进行虚拟对准。因此，本文提出了一种简单的校准程序，该程序基于 MIMU 的读数，将 MIMU 的惯性框架与 ISB 推荐的解剖框架对齐。该校准程序包括 5 秒的中立姿势静立，然后进行 10 次连续的髋关节屈伸运动。该程序可以独立校准连接到骨盆、大腿、小腿和脚部的 MIMU。通过对 10 名健康参与者的实验研究，验证了校准程序和 3D 关节角度估计的准确性和可重复性，该研究与黄金标准运动捕捉系统进行了比较。该程序在将 MIMU 框架与其相应的解剖框架对齐方面具有很高的测试-重测可重复性，即 MIMU 和解剖框架之间的螺旋角在测试和重测期间没有显着差异（除了大腿 MIMU 之外）。与之前介绍的程序相比，该程序达到了最高的组内可重复性（螺旋角的组内变异系数：20.5-42.2%）。此外，与未经校准的 3D 关节角度估计相比（平均高达 26.3 度），该校准程序可以减少 3D 关节角度估计的偏移误差（平均高达 12.8 度）。该校准程序使 MIMU 能够测量具有临床意义的步态运动学。
