Saskia Baltrusch

157 Chapter 6 50 Nm with three beams with a diameter of 4.7 mm. Furthermore, a clutch is implemented in the device to provide the possibility of switching on and off the support torque generated by device around the hip joint (Figure 1c). The clutch features an angle-adjustable locking mechanism (Corrective System Joint 17BK1, Otto Bock Healthcare GmbH, Duderstadt, Germany). The joint connection consists of bearing washers and bushing and is fixed with a joint nut. A locking wedge locks the joint at the desired trunk inclination angle. Continuous angle adjustment is possible due to a worm gear and toothed wheel. If switched on, the clutch engages the springs in the hip actuator. If switched off, these springs are disengaged and the exoskeleton does not provide support via the hip actuators, allowing unobstructed hip flexion. If the clutch is engaged at an inclination angle >0, it will cause the torque vs hip angle profile to shift forward. Thus, the same torque will be reached 15 degrees later in the forward flexion. Figure 1: The exoskeleton unloads the back by applying a force at the torso, pelvis, and the thighs: (a) an elastic spinal module generates a torque through a set of carbon fiber beams and (b) a passive hip actuator. The implemented clutch allows disengagement of the passive hip actuators, by moving a manual switch (c) . Note: electrical wires were used for measurements and are not part of the exoskeleton. 2.2 Participants We recruited employees from the Dutch airline company KLM, working in the luggage handling department and employees from the Dutch automotive industry Mitsubishi Turbochargers, working as operators and being responsible for assembling and sorting turbochargers. Both companies have high prevalence of low-back pain among their employees. 6