Figure 2

Arm kinematics. 2 IMUs per arm (blue lines), only 1 IMU on the upper arm (red lines), and only 1 IMU on the forearm (green lines) sensor placement options are presented. SH, EL, and H represent shoulder, elbow, and hand positions, respectively. φ stands for the elbow flexion angle, l _UA and l _FA represent upper and forearm segment lengths, while ε _UA and ε _FA stand for Euclidean distances of upper and forearm sensor placement simplifications. R _UA and R _FA indicate upper and forearm coordinate systems.