Fig. 3
From: Automated, IMU-based spine angle estimation and IMU location identification for telerehabilitation
The procedure for joint angle estimation involves a four-step algorithm. Firstly, the orientation of the sensors relative to the global coordinate system is estimated. Secondly, calibration is performed to determine the relative orientation of human body segments in relation to their corresponding IMUs. Thirdly, the relative orientation of the distal segment with respect to the proximal segment is calculated. Finally, the joint angle is derived from the relative orientation. It’s important to note that the fourth step is not illustrated in the figure