An Automatic Foot and Shank IMU Synchronization Algorithm: Proof-of-concept

Area of Science:

• Biomechanics
• Wearable Technology
• Human Performance Analysis

Background:

• Synchronizing data from multiple wearable sensors is crucial for accurate human performance analysis.
• Existing methods for synchronizing sensor data, particularly for lower limb biomechanics, can be complex or imprecise.
• Accurate synchronization is essential for calculating joint angles and analyzing gait kinematics and kinetics.

Purpose of the Study:

• To develop and demonstrate a novel synchronization technique for inertial measurement units (IMUs) on the shanks and insoles on the feet.
• To enable accurate computation of ankle joint angles and concurrent analysis of gait kinematic and kinetic features.
• To provide an alternative, reliable approach to sensor system synchronization in biomechanical research.

Main Methods:

• A synchronization algorithm based on the cross-correlation of gyroscope sensor data from shank-mounted and foot-mounted IMUs was developed.
• The algorithm was validated by comparing its output to sensor data synchronized using manually annotated heel-strike and toe-off ground-truth landmarks.
• The technique was tested on both healthy participants and individuals with knee osteoarthritis.

Main Results:

• The developed algorithm successfully synchronized data from shank and foot sensors.
• Validation against ground-truth landmarks showed a mean lag time bias of 25.56ms.
• The synchronization technique proved effective across different participant groups, including those with knee osteoarthritis.

Conclusions:

• The proposed cross-correlation-based algorithm provides an effective method for synchronizing IMUs on the shanks and insoles.
• This technique facilitates the computation of ankle joint angles and enables integrated analysis of gait kinematics and kinetics.
• The study offers a practical and validated alternative for sensor synchronization in wearable biomechanics research.