The effects of different control methods on human biomechanics during exoskeleton walking

Abstract

Ever since human ancestors picked up rocks and used them as tools, technology has enhanced human capabilities. Over the last decades more and more research has been done in trying to enhance strength and endurance by means of an exoskeleton. Reducing the metabolic cost of human walking using lower extremity exoskeletons is one of the challenges that has been taken on by several research groups. Only recently have some of these groups managed to reduce the metabolic cost of walking with the help of an exoskeleton. Understanding how human walking behavior changes and adapts to these new supportive devices is crucial in the quest to better, more efficient exoskeletons. Effects of two control methods, that were proven to be successful in making human walking more energy efficient, on the biomechanics of human subjects were examined by performing lab experiments and using the collected experimental data to run musculoskeletal simulations to compute muscle mechanics and energetics of six lower extremity muscles. Lab experiments, which were completed by eight out of ten recruited subjects, consisted of treadmill walking with and without the exoskeleton, while EMG, respiratory, kinematic and kinetic data was recorded. Processing of this data, the simulation steps taken and the eventual results are presented in this thesis. It was found that walking with the exoskeleton, while it was not giving any assistance, significantly increased the energy consumption rate of subjects, compared to normal walking. This increase was reduced by one of the two support methods, whereas the other had no significant effect on the total metabolic rate.