Towards gait-pattern adaptation algorithms for exoskeletons based on the ZMP criterion

This paper presents a gait-pattern adaptation algorithm for exoskeletons based on the Zero Moment Point criterion. The proposed exoskeleton is developed for lower limbs and based on a commercially available orthosis. The step length and duration are considered as the adaptation parameters, they are computed through minimization based on direct dynamics and considering the orthosis-patient interaction forces. Also, a robust controller based on the ℋ_∞ method is designed to attenuate the effects of external disturbances and parametric uncertainties in the trajectory tracking errors. The dynamic model of the actual exoskeleton, with interaction forces included, is used to generate simulation results.