This paper presents and experimentally demonstrates a novel framework for variable assistance on lower body exoskeletons, based upon safety-critical control methods. Existing work has shown that providing some freedom of movement around a nominal gait, instead of rigidly following it, accelerates the spinal learning process of people with a walking impediment when using a lower body exoskeleton. With this as motivation, we present a method to accurately control how much a subject is allowed to deviate from a given gait while ensuring robustness to patient perturbation. This method leverages control barrier functions to force certain joints to remain inside predefined trajectory tubes in a minimally invasive way. The effectiveness of the method is demonstrated experimentally with able-bodied subjects and the Atalante lower body exoskeleton.
@article{arxiv.1909.11188,
title = {Towards Variable Assistance for Lower Body Exoskeletons},
author = {Thomas Gurriet and Maegan Tucker and Alexis Duburcq and Guilhem Boeris and Aaron D. Ames},
journal= {arXiv preprint arXiv:1909.11188},
year = {2019}
}