Axis calibration algorithms for IMU sensor-based motion tracking system

Abstract

This thesis proposes an algorithm and calibration protocol for calibrating the axes of an inertial measurement unit (IMU) sensor attached to the body, regardless of its orientation or position, to align with the user’s desired virtual axes. The axis calibration process consists of two steps: aligning the sensor’s Z-axis with the local frame’s Z-axis and aligning the X-axis, which measures Extension/Flexion crucial in human walking, with the body reference frame’s X-axis. When applying this process to an experimental setup where the direction of rotation is limited to one direction, with the IMU sensor attached in an arbitrary direction, the calibrated Roll axis rotation angles corresponded with the rotation angles obtained from the experimental equipment’s encoders. When the IMU sensor was attached to the body for walking, the Roll axis rotation angles obtained through axis calibration matched those derived from motion capture data.