Saskia Baltrusch

244 Chapter 9 force will substantially reduce the population at risk [11,12]. For these reasons, the exoskeleton may contribute to preventing work-related low back pain for people executing highly demanding tasks, such as repetitive lifting in a working environment like a luggage handling hall at an airport. Still, the SPEXOR exoskeleton is a prototype and implementing it in a vocational setting requires more research and design improvements. Especially the user satisfaction results indicate that the device is still far from being ready for implementation in the field, as only about 50% of employees considered to wear the exoskeleton daily during their job. The results have several implications for the future design of passive trunk exoskeletons. First, design characteristics of the SPEXOR exoskeleton that still need to be improved are the mass of the exoskeleton and its dimension. The current mass decreases comfort and makes the device less suitable to be worn for a whole working day. In addition, the dimension of the hip actuators restricts arm swing. Moving the actuators to a different location needs to be considered in the next design step. Also, the results have shown that both, perceived support and actual support given by the device still need to be improved to reach higher user satisfaction. Increasing the perception of support is challenging. As participants in this study varied in terms of low-back pain and related restrictions experienced, their perception of how much support is needed, was different. This would ask for individual design adaptation and a tunable, or self-regulating support. To reach increased support delivered by the device, the stiffness of the exoskeleton could be increased, e.g. by changing the pretension of the hip actuators or by using carbon beams of a higher stiffness for the spinal module. However, an increase in stiffness will always come with a decrease in ROM and further testing of the exoskeleton would be needed to find the optimal stiffness- ROM trade-off. A solution for achieving higher support levels and a support that is tunable and can be regulated by the user, could be the addition of active control and actuation of the exoskeleton. Motors can provide additional, task-dependent and/or user controlled support at given time points, such as at peak moment or peak flexion. The design of an active exoskeleton is ongoing work in the SPEXOR consortium.