Dynamic optimization of anchor points positions in a cable driven exosuit: a computer simulation approach

Abstract

The purpose of this study is to simulate the different walking adaptation strategies and their impact on muscle activities while changing the anchor point position of an exosuit in hip extension assistance motion. In particular, muscle activation and metabolic power consumption are assessed at varying levels of assistive force actuation that alters the position of anchor points. OpenSim software was used to perform simulations of 10 elderly subjects at comfortable gait speed while varying the anchor point positions of the thigh. Compared to unassisted gait, the extension assistance at placements below 40% (proximal) requires an increase in metabolic cost to maintain gait characteristics. At 40%, energy consumption corresponds to unassisted gait. From 50% proximal to distal positions, a reduction in metabolic cost is observed, with a minimum at 80%. The variation of the metabolic cost at different positions of the anchor point is reflected in the muscular activities, with an increase when the cable is placed below 40% of the total length of the thigh and a decrease from this position onwards. The activation level and metabolic cost exerted by the hip flexors and extensors muscles may be optimized during the exosuit actuation. The dynamics of the muscles spanning joints not actuated by the exosuit are not influenced by the actuation. The results and analysis provide information to optimize actuation profiles in the design of exosuits to assist gait for older adults and, thus, promote active aging and improving rehabilitation routines.