Drift-Free Foot Orientation Estimation in Running Using Wearable IMU.

Area of Science:

• Biomechanics
• Sports Science
• Sensor Technology

Background:

• Foot-worn inertial sensors are valuable for motion analysis but suffer from orientation drift.
• Existing methods for drift correction are often inadequate for the dynamic demands of running.
• Accurate foot orientation is crucial for understanding running biomechanics and injury prevention.

Purpose of the Study:

• To introduce and validate a novel method for estimating and correcting orientation drift in foot-worn inertial sensors.
• To improve the accuracy and precision of foot orientation measurement during running.
• To compare the proposed method against traditional zero-velocity update techniques.

Main Methods:

• A modified strap-down integration (MSDI) algorithm was developed to reduce initial orientation drift.
• Joint center acceleration (JCA) estimation from a two-segment foot model was used for further drift compensation.
• The method was validated against an optical motion-tracking system in 26 runners at various speeds (8, 12, 16 km/h).

Main Results:

• The proposed method achieved high accuracy (0.4 ± 3.8°) and precision (3.0 ± 1.8°) for foot orientation during mean stance.
• Orientation estimation before initial contact showed improved accuracy (2.0 ± 5.9°) and precision (1.6 ± 1.1°) compared to zero-velocity update methods.
• The study analyzed the impact of initial and terminal contact detection errors on orientation parameters.

Conclusions:

• The novel MSDI with JCA compensation effectively reduces orientation drift in foot-worn inertial sensors during running.
• This method offers superior accuracy and precision for foot orientation measurement in running compared to conventional techniques.
• The findings have implications for more reliable biomechanical analysis of running using wearable sensors.