Design of a Hand Exoskeleton for Space Extravehicular Activities

Due to the bulk and stiffness of the astronauts’ glove, so called Extravehicular Activity (EVA) glove, many problems occur during their missions outside the spacecraft i.e. fatigue, dexterity reduction, decrease of possible EVA hours, etc. [1, 2]. To solve these problems a hand exoskeleton which can be embedded inside the astronauts’ glove has been proposed as a solution to help them to move their fingers more easily. In this work all the steps that were taken towards the design of a preliminary version of the hand exoskeleton are explained in detail. The paper starts with a brief survey on related literature, followed by an analysis of three main research subjects for the design and realization of the hand exoskeleton: sensors, actuators and structure. In particular, different kinds of sensors and actuators are evaluated and advantages and disadvantages of each one are investigated. Then the main reasons to choose a specific type of sensor or actuator are described in detail. Regarding the structure, different possible solutions converging towards an optimal design for this application have been evaluated. Moreover, the use of some springs in the structure to simulate the stiffness of the EVA glove is proposed in order to be able to test the device in a condition similar to its final application. A brief description about the kinematic modeling and simulation of the structure in order to find the optimum location of the transmission cables and their tension forces is explained.