Towards Variable Assistance for Lower Body Exoskeletons
This work addresses the need for more adaptive exoskeleton control to accelerate spinal learning in people with walking impediments, representing an incremental improvement over existing methods.
The paper tackles the problem of rigid gait adherence in lower body exoskeletons by introducing a variable assistance framework that allows controlled deviation from a nominal gait, using safety-critical control methods to ensure robustness to perturbations, and demonstrates its effectiveness experimentally with able-bodied subjects and the Atalante exoskeleton.
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.