Stable gait generation method for lower-limb exoskeleton based on instrumented crutches

Lower-limb exoskeletons have attracted considerable interest because they can provide impaired individuals with the ability to walk upright. Trajectory generation of walking gait is a crucial issue for lower-limb exoskeletons that has not yet been satisfactorily solved. The purpose of this article is to study a stable gait generation method considering the subjective walking intention. Inspired by the motion synergy between crutches and lower limbs, a stable gait generation method for flat-ground walking was proposed for a lower-limb exoskeleton. The motion synergy in the sagittal plane between the crutch-pitch-angle and step length was validated using theoretical and experimental methods. The synergistic relationship between the maximum crutch-pitch-angle and step-length coefficient was established and optimized. Based on the synergistic relationship, the gait trajectory of the exoskeleton with variable step length can be instinctively generated with a crutch swing. The gait stability of the human-exoskeleton system was modeled and analyzed. Consecutive walking experiments were conducted on flat ground in which a compact lower-limb exoskeleton and pair of instrumented crutches were employed. The results demonstrate that gait based on the synergistic relationship is effective and stable, thereby verifying the feasibility of this human-in-the-loop gait generation method.