Saskia Baltrusch

136 Chapter 5 3D Kinematics of both the subject and exoskeleton were measured with an optical motion capture system (Certus Optotrak, Northern Digital, Waterloo ON, Canada) at 50 Hz. Marker clusters were attached on one side of the body, to the shank (A), thigh (B), pelvis (C), thorax (D), upper arm (E), and forearm (F) (Figure 8B). In addition, marker clusters were attached to relevant parts of the exoskeleton; exo hip joint (1), exo pelvis frame (2), exo base spinal structure (3), and exo top spinal structure (4). For all modeled human body segments (foot, shank, thigh, pelvis, abdomen, thorax, head, upper arm, forearm, and hand), anatomical coordinate systems were calculated based on anatomical landmarks that were related to the corresponding marker clusters using a probe with six markers [39]. From the rotation matrices of the segments, joint angles were calculated using Euler decomposition (YXZ). The angles that were used in the analysis are defined in Figure 8A. From the angle time-series (Figure 10), peak angles were subtracted and compared between conditions. Figure 8: Angle definitions for the human and the exoskeleton (A) . Knee angle (a), hip angle (b), lumbar angle (c), trunk angle (d), pelvis inclination (e), exo hip angle (f), exo lumbar angle (g), exo trunk angle (h), exo pelvis inclination (i), Measurement setup (B) . Subject equipped with the exoskeleton and markers to track the position and orientation of different body parts (red). The position and orientation of the lower leg (A), upper leg (B, not visible in this photograph), the pelvis (C) , the trunk (D) the upper arm (E) , and the lower arm (F) are tracked. Additionally, the exoskeleton is equipped with marker clusters to track the exoskeleton (yellow) hip angle (1) the pelvis carbon fiber frame at the hip (2) the pelvis carbon fiber frame at the base of the spinal exoskeleton structure (3) top of the spinal exoskeleton structure (4). Various single markers were used to track individual parts of the exoskeleton, but are not further used in the analysis and therefore not further elaborated. The stick figures show a visualization of the tracking results. For the sake of clarity, the body markers (red) are not highlighted in this figures. In the middle the subject is standing upright. The pink lines represent body parts of the subject, while the turquoise color represents the exoskeleton structure. On the right, the subject is performing a stoop. Written informed consent was obtained from the participant to publish this picture.