Locomotion control strategy of hydraulic lower extremity exoskeleton robot

Soldiers often should carry heavy loads on their back for a long time during military operations. To this end, exoskeleton robots have been developed to enhance mobility and reduce the muscle fatigue caused by heavy loads. This paper presents a locomotion control strategy for a hydraulic lower extremity exoskeleton robot developed for military purposes. The robot utilized the dual-mode control scheme, which is comprised of the active control for the stance phase and the passive control for the swing phase, to achieve high walking speed in the swing phase while supporting heavy loads in the stance phase. To reduce the sudden change of the torque command at the transition from the swing phase to the stance phase, a smoothing method is adopted. We also implemented a pre-transition method to take a foot off quickly for fast walking by predicting the change from the swing to the stance in advance. The experiment results show that a wearer can walk at a speed of up to 4 km/h on a treadmill with a 45 kg backpack load.