Soft wearable device for lower limb assistance: Assessment of an optimized energy efficient actuation prototype

There is a shared trend, in engineering fields related to robotics, to privilege soft systems on behalf of hard ones. This direction stems from the desire of designing and implementing energetically efficient systems that are light, soft, wieldy, reconfigurable and with augmented dexterity. Soft wearable devices will also improve very important characteristics such as wearability and comfort. The design and implementation of a wearable system meeting these requirements is being developed in the XoSoft EU project. In this work we present the design of a soft modular energy-efficient lower limb exoskeleton. It is based on an energy efficiency analysis optimization. Novelty of this work is given by the integration of quasi-passive actuations in a soft exoskeleton. The goal is to assist-during daily tasks-subjects with low to moderate mobility impairments reducing by 10% to 30% the mechanical energy requirements and improving the gait (stability, tiredness, etc). Assistance is meant to be on hip, knee and ankle, in a unilateral or bilateral configuration. A first modular single-joint prototype is described, developed and assessed on a post-stroke patient gait. The comparison between the validation and the simulation showed a similar behavior and an energy reduction of 7.8%. The overall measured assistance given by the exoskeleton on the user's hip segment in terms of power is 9.3%.