Investigation on variable impedance control for modulating assistance in walking strategies with the AUTONOMYO exoskeleton

Abstract

Impedance based control is an established strategy to provide assist-as-needed power support in rehabilitation. The studied control in this paper differs, however, from the standard approach. Instead of following a defined spatio-temporal motion where the assisting torques depends on the capacity of the user to follow a trajectory, the controller is divided in gait phases with constant impedance parameters. This approach should allow more freedom of the user and simple adaptability of assistance level to the user condition. The simulated gait pattern relies on three states (swing, stance and a double support phase) which are associated to different spring-like impedances. In this paper, we investigate the relation between the gait and parameters such as the spring stiffness and the attractive position. Results show that both the user and the impedance’s parameters can influence gait characteristics such as step length, cadence, walking velocity.