Natural user-controlled ambulation of lower extremity exoskeletons for individuals with spinal cord injury

Abstract

Natural-quality, independent ambulation is a prerequisite for community use of lower extremity exoskeletons by individuals with disabilities. In general, current exoskeletons generate pre-programmed gait, where the user cannot exercise volitional control necessary to navigate over uneven surfaces and avoid obstacles. This project introduces an intuitive control strategy that allows the user to determine and sense the exoskeleton movement in real time using trajectories produced by the hands. The concept allows neurally defined ambulation control to be expressed through alternative biological articulators. This novel approach uses admittance control to compute each exoskeleton’s foot position from Cartesian forces exerted by the user’s hand on a trekking pole that is connected to foot through a multi-axis load cell. The algorithm has been evaluated by naïve, non-disabled users who walked a 10 degree of freedom, ½ scale biped robot on a treadmill. The results show that the algorithm produced robot-generated gait kinematics that are similar to human gait kinematics. A human-scale exoskeleton has been developed to allow further exploration of this control method.