A new method of measuring the stiffness of astronauts' EVA gloves

Hand fatigue is one of the most important problems of astronauts during their missions to space. This fatigue is due to the stiffness of the astronauts’ gloves known as Extravehicular Activity (EVA) gloves. The EVA glove has a multilayered, bulky structure and is pressurized against the vacuum of space. In order to evaluate the stiffness of EVA gloves, different methods have been proposed in the past. In particular, the effects of wearing an EVA glove on the performance of the hands have been published by many researchers to represent the stiffness of the EVA glove. In this paper, a new method for measuring the stiffness of EVA gloves is proposed. A tendon-actuated finger probe is designed and used as an alternative to the human index finger in order to be placed inside an EVA glove and measure its stiffness. The finger probe is equipped with accelerometers, which work as tilt sensors, to measure the angles of its phalanges. The phalanges are actuated by applying different amount of torque using the tendons of the finger probe. Moreover, a hypobaric glove box is designed and realized to simulate the actual operating pressure of the EVA glove and to measure its stiffness in both pressurized and non-pressurized conditions. In order to prove the right performance of the proposed finger probe, an Orlam-DM EVA glove is used to perform a number of tests. The equation of stiffness for the PIP joint of this glove is extracted from the results acquired from the tests. This equation presents the torque required to flex the middle phalanx of the glove. Then, the effect of pressurization on the stiffness is highlighted in the last section. This setup can be used to measure the stiffness of different kinds of EVA gloves and allows direct, numerical comparison of their stiffness.