A Reduced Gravity Simulation System for Astronauts Training Based on Lower Limb Exoskeleton Robot

Reduced gravity simulation systems are important for astronaut training because microgravity can have some adverse effects on the human body. However, there is a lack of a small device that can simulate a reduced gravity environment and fewer analyses of the effects of microgravity on the human body. For this reason, we designed a reduced gravity simulation system based on a vertical body weight support system (BWS) and an exoskeleton. The BWS simulates the effects of reduced weight of the whole body by suspending a certain weight. The exoskeleton monitors the angle of the wearer's lower limb joints through a inertial measurement unit net on the body to map the corresponding joint moments, and ultimately realizes the reduced gravity simulation of hip joint. Based on the system described above, we wish to explore the effects of microgravity on human biomechanics while trying to ensure the simulations are as accurate as possible. One subject was recruited to participate in a series of experiment. Walking experiment was conducted at two speeds under three wearing conditions: without the BWS and exoskeleton, with the BWS and with the BWS and exoskeleton. Biomechanical data, including joint angles, joint moments, and muscle activations, were recorded by a motion capture system and surface EMG during the experiments. Based on these measurements, the effects of reduced gravity simulation environment on the walking patterns were mainly in the joint angles, joint moments, muscle activation, and control strategies of the human body. It is worth noting that the activation intensity of some muscles increased by different magnitudes and shifted in phase under the simulation condition compared to the normal. These results were unexpected for us and promising to serve as an inspiration for the future development of astronauts training system. Data can be found at Github (https://github.com/Xianhl25/RGS.git).