The exoskeleton robots to assist load-carrying have received much attention in recent years. However, their load capacity and comfort are still insufficient. In this paper, we have developed a novel parallel actuated lower limb exoskeleton(PALExo), that addresses these problems. The novelty is that each limb of the exoskeleton is a 2-SPU underactuated parallel mechanism. Owing to the innovative series elastic module (SEM) with multi-segment stiffness, PALExo is compliant and comfortable for the wearer. The high load characteristic of the parallel structure increases the exoskeleton load capacity, and it can accommodate wearers of different heights without manual adjustment. A dynamic model of the exoskeleton was established, and in order to increase the robustness of the system, we designed a force control method based on sliding mode control and disturbance observer. Finally, the rationality and load-bearing effect of the exoskeleton were verified through a series of experiments including swing following, squatting and walking with loads.
In order to meet the assist requirements of extravehicular activity (EVA) for astronauts, such as moving outside the international space station (ISS) or performing on-orbit tasks by a single astronaut, this paper proposes an astronaut robotic limbs system (AstroLimbs) for extravehicular activities assistance. This system has two robotic limbs that can be fixed on the backpack of the astronaut. Each limb is composed of several basic module units with identical structure and function, which makes it modularized and reconfigurable. The robotic limbs can work as extra arms of the astronaut to assist them outside the space station cabin. In this paper, the robotic limbs are designed and developed. The reinforcement learning method is introduced to achieve autonomous motion planning capacity for the robot, which makes the robot intelligent enough to assist the astronaut in unstructured environment. In the meantime, the movement of the robot is also planned to make it move smoothly. The structure scene of the ISS for extravehicular activities is modeled in a simulation environment, which verified the effectiveness of the proposed method.
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