An IMU-to-Body Alignment Method Applied to Human Gait Analysis.

Area of Science:

• Biomechanics
• Wearable Technology
• Sensor Calibration

Background:

• Accurate placement and alignment of inertial sensors are crucial for reliable motion analysis.
• Existing methods often require specialized tools or complex procedures.
• Inertial Measurement Units (IMUs) are widely used in gait analysis but are sensitive to sensor orientation.

Purpose of the Study:

• To present a novel, simple, and tool-free calibration procedure for aligning inertial sensors with body segments.
• To validate the proposed calibration method across different applications, including simulation, a simplified joint model, and human gait analysis.
• To assess the accuracy and potential limitations of the calibration procedure in real-world scenarios.

Main Methods:

• Development of a novel calibration procedure for inertial sensor alignment.
• Validation through computer mathematical simulation.
• Experimental validation using a simplified physical joint model.
• In-vivo validation with five able-bodied subjects during a gait test.

Main Results:

• Simulation results confirmed accurate joint angle measurements irrespective of initial sensor placement after calibration.
• The method performed correctly in simplified joint and real gait tests, though secondary plane errors were observed.
• Observed errors in experimental tests are attributed to current IMU technology and data fusion algorithm limitations.

Conclusions:

• The presented calibration procedure offers a simple and effective solution for the sensor alignment problem in IMU-based gait analysis.
• The method demonstrates robustness across simulated and experimental conditions.
• Further improvements may depend on advancements in IMU hardware and sensor fusion algorithms.