Exoskeleton based microgravity simulation for astronaut training

Zusammenfassung (Abstract) :

In this work we present our recent research in the field of exoskeleton-based astronaut training. Astronauts on space missions are exposed to different challenges, one being the adaptation to microgravity. Today they are only two ways, to simulate microgravity and train astronauts for coping with the absence of gravity, first there are parabolic flights, where it Is possible to generate microgravity for short time periods of about 22 seconds, which is not much for really adjusting to the absence of gravity even so one can fly consecutive parabolas, but there are always two phase of hyper gravity with approximately 1.8g in between the 22 seconds of zero gravity. The second possibility is training in big water basins where the astronauts wear their space suits, due to the buoyancy effect astronauts do not feel their weight but need to overcome the water resistance which makes the weightlessness feeling not comparable to real microgravity. Besides the short time of zero gravity during parabolic flights and the inaccurate simulation of zero gravity in water basins, both possibilities are very complex and need expensive equipment. To overcome the problems, we propose a method to compensate for the weight of a human arm with an active upper body exoskeleton. The active exoskeleton has 4 active degrees of freedom, three in the shoulder and one in the elbow, and is torque controlled. For compensation of the arm weight, we generate a subject-specific arm model in two steps. In the first step, we generate a model which is based on the total bodyweight and the height of the subjects as well as the length of the upper and lower arms. From this information, a rough estimate of the arm weight is calculated and integrated into the dynamic model of the exoskeleton. With this method the weight of the arm can already quite good be compensated, for a fine tuning we actively move the exoskeleton with the subject relaxing its arm in the exoskeleton, from the position differences accruing due to not 100% correct weights, we gradually adapt the model to reduce the error between the model and real human arms. With this method, we can provide an accurate microgravity simulation on earth and a cost-efficient training method for astronauts.

Stichworte :

exoskelton, astronaut training