TY - JOUR

T1 - Self-Calibrating Magnetometer-Free Inertial Motion Tracking of 2-DoF Joints

AU - Laidig, Daniel

AU - Weygers, Ive

AU - Seel, Thomas

N1 - Funding Information: This work has partially been conducted in the project BeMobil, which is supported by the German Federal Ministry of Research and Education (FKZ 16SV7069K).

PY - 2022/12/15

Y1 - 2022/12/15

N2 - Human motion analysis using inertial measurement units (IMUs) has recently been shown to provide accuracy similar to the gold standard, optical motion capture, but at lower costs and while being less restrictive and time-consuming. However, IMU-based motion analysis requires precise knowledge of the orientations in which the sensors are attached to the body segments. This knowledge is commonly obtained via time-consuming and error-prone anatomical calibration based on precisely defined poses or motions. In the present work, we propose a self-calibrating approach for magnetometer-free joint angle tracking that is suitable for joints with two degrees of freedom (DoF), such as the elbow, ankle, and metacarpophalangeal finger joints. The proposed methods exploit kinematic constraints in the angular rates and the relative orientations to simultaneously identify the joint axes and the heading offset. The experimental evaluation shows that the proposed methods are able to estimate plausible and consistent joint axes from just ten seconds of arbitrary elbow joint motion. Comparison with optical motion capture shows that the proposed methods yield joint angles with similar accuracy as a conventional IMU-based method while being much less restrictive. Therefore, the proposed methods improve the practical usability of IMU-based motion tracking in many clinical and biomedical applications.

AB - Human motion analysis using inertial measurement units (IMUs) has recently been shown to provide accuracy similar to the gold standard, optical motion capture, but at lower costs and while being less restrictive and time-consuming. However, IMU-based motion analysis requires precise knowledge of the orientations in which the sensors are attached to the body segments. This knowledge is commonly obtained via time-consuming and error-prone anatomical calibration based on precisely defined poses or motions. In the present work, we propose a self-calibrating approach for magnetometer-free joint angle tracking that is suitable for joints with two degrees of freedom (DoF), such as the elbow, ankle, and metacarpophalangeal finger joints. The proposed methods exploit kinematic constraints in the angular rates and the relative orientations to simultaneously identify the joint axes and the heading offset. The experimental evaluation shows that the proposed methods are able to estimate plausible and consistent joint axes from just ten seconds of arbitrary elbow joint motion. Comparison with optical motion capture shows that the proposed methods yield joint angles with similar accuracy as a conventional IMU-based method while being much less restrictive. Therefore, the proposed methods improve the practical usability of IMU-based motion tracking in many clinical and biomedical applications.

KW - anatomical calibration

KW - elbow joint

KW - human motion analysis

KW - inertial measurement unit

KW - inertial sensor

KW - kinematic constraints

KW - sensor-to-segment calibration

UR - http://www.scopus.com/inward/record.url?scp=85144563037&partnerID=8YFLogxK

U2 - 10.3390/s22249850

DO - 10.3390/s22249850

M3 - Article

C2 - 36560219

AN - SCOPUS:85144563037

VL - 22

JO - Sensors

JF - Sensors

SN - 1424-8220

IS - 24

M1 - 9850

ER -