Motion Adaption and Trajectory Generation of Stair Ascent and Descent with a Lower Limb Exoskeleton for Paraplegics

In this work, joint trajectory generation of lower limb exoskeleton for stair ascent and descent are investigated. The motions are generated by a series of gait states with transitions at specific intervals. The joint trajectories are planned in joint space by interpolating the joint angles of assigned gait states with the dimensions of stairs and wearer. In order to generate the adaptive motion for various dimensions of stairs, multiple sensors and motion adaption strategy with sensing information and fuzzy logic inference are developed to ensure enough foot contact area and to avoid foot-stair collisions. Simulations and experiments of the generated joint trajectories and motion adaptation strategy are conducted on a lower limb exoskeleton. Results show that the proposed joint trajectories provide smooth assistance and the generated motion successfully adapts to various size of stairs.