Saskia Baltrusch

127 Chapter 5 Figure 4 : (Left) Passive Spexor prototype. An elastic spinal module in the back is used to provide a large range of motion and to store energy. Several misalignment compensating mechanisms at the hip and the back (hip indicated in the figure) are implemented. A passive, parallel elastic torque source provides support at the hip; (Right) Kinematic equivalent representation. The spinal structure is comprised of a ball joint and a linear slider in combination with elastic beams (here represented as two hinge joints in series). This structure provides flexibility and compensates for potential misalignment. The hip structure consists of three parallel hinge joints in combination with a fourth, actuated hinge joint in series with a linear joint. This structure fulfills a dual function, once as a fitting mechanism and once as a misalignment compensating structure. Written informed consent was obtained from the participant to publish this picture. Hip Structure Concept For the flexion and extension of the hip joint, a mechanism with many adjustment possibilities was chosen. Simple models from the literature [10] indicate that the required torque for the hip joint has a sinusoidal profile. The goal was to replicate this torque profile with adjustment possibilities (Figure 3B) in the torque magnitude [34]. Alignment of the rotation axis of a human and an exoskeleton is challenging [16]. For the flexion and extension and abduction, an approach was chosen, where a certain amount of misalignment is accepted and compensated for by the device kinematics (Figure 2E and for more detail Figure S1), i.e., the rotational joints and the slider along the leg move to accommodate for the misalignment. 5