Development Of EVA Spacesuit Arm Service Life Test System Based On External Drive Arm

EVA (extra-vehicular activity) spacesuit arm is composed of fabric layers, which retain the suit atmosphere and maintain the shape of the pressure suit. The restraint layer restricts radial expansion of the spacesuit, providing joint articulations, and preventing the arms from lengthening when the spacesuit is pressured. Bending joints on the spacesuit arm, known as flat-pattern joints, are formed by sewing pleats into the fabric on the outer side of the joint. Making a compromise between reliability and mobility is usually a high priority when design the spacesuit. When astronauts wearing spacesuit work in the space, it would result in fatigue of the material after joints of spacesuit arm bend and stretch for a long time. Leakage and failure of the pressure spacesuit is inevitable, and it is really important to know the span of service life of the spacesuit arm.Manual test of spacesuit arm service life is inefficient, and it’s hard to obtain the test data. The primary aim of this thesis is to design an advanced EVA spacesuit arm service life test system. The service life test system, which based on external drive robot arm, can make it easy to carry out the service life test efficiently. The internal space of spacesuit arm is narrow, and the fabric inside is vulnerable to damage. It’s the key point to design humanoid robot arm, which could drive the spacesuit arm joints bending and stretching for tens of thousands times.Based on the characteristics of the spacesuit arm, a mathematical model using D-H method is developed to describe the motion trajectory of the spacesuit arm. Kinematics analysis and simulation of two DOF spacesuit arm model is carried out using Matlab. Multiple design schemes of spacesuit arm drive devices are presented, and advantages as well as disadvantages of each design schemes are discussed. An advanced spacesuit arm service life test system based on external drive robot arm, which shoulder joint and elbow joint are externally driven by pneumatic swing cylinder respectively, is proposed eventually. The test system contains internal passive robot arm which can adapt to spacesuit arm of different dimensions by changing the length of upper arm. Internal passive robot arm simulates the real arm and it improves the quality of spacesuit arm movement. The pneumatic system and the measurement & control system are composed by sensors, pneumatic control valve and NI DAQ board. And the computer software of test system is programed by Labview. The results of EVA spacesuit arm service life test show that the system with external drive robot arm can carry out the test efficiently and it’s easy to obtain the test data. The advanced EVA spacesuit arm service life test system developed in this paper is significant for the study of the reliability of EVA spacesuit.