Abstract:
Online gait control in human-powered exoskeleton systems is still rich research field and represents a step
towards fully autonomous, safe and intelligent navigation. Admittance Controller performs well on flat terrain
walking in human-powered exoskeleton systems for acceleration and slowdown. We are the first who proposed
Variable Admittance Controller (VAC) for smooth stair climbing control in Human-Powered Exoskeleton Systems.
Trajectory correction technique transforms the interaction forces exerted on the exoskeleton from the pilot to
appropriate intended joint flexion angles through dynamic viscoelastic models. We demonstrate the proposed control
strategy on one degree-of-freedom (1-DOF) platform first, and then extend to the Human power Augmentation
Lower Exoskeleton (HUALEX). The experimental results show that the proposed gait transition control strategy can
minimize the interaction dynamics with less interaction force between the pilot and the exoskeleton compared to
the traditional admittance controller. Compared to Ordinary Admittance Controller, the proposed VAC significantly
improve the normalized Mean Squared Error (nMSE) of trajectory tracking from 2.751° to1.105°.
