# Prototype Design and Performance Tests of Beijing Astronaut Robot
## 1 Introduction  
With the development of space technology, a space station is a vital approach for human beings to study and research space, but its construction and maintenance require extravehicular activity (EVA) carried out by astronauts [1]. Since the space environment has the characteristics of high vacuum, large temperature differences, high radiation, and microgravity, which result in the failure of continuous working time and inefficiency, humans in space require a large and a complex life support system, an environmental control system, and life-saving system, and requires a lot of uninterrupted material supply [2]. Under such conditions, space operations of astronauts are not only dangerous but also costly. Therefore robots are used as assistants or replacements more and more frequently to reduce the risk and cost. In addition, space robots do better in load capacity, accurate positioning, adaption to environments, and durable work. Space robots can install precise devices, maintain the space station, and perform experiments in space without health concerns [3].  
So far, a few robotic arms have been applied in the International Space Station which is being assembled in low Earth orbit, for example Canadarm2 [4] and Robonaut [5]. Canadarm2 was designed by the Canadian Space Agency and it is used mainly for payload handling, EVA support, and the internationalspace station's assembly [6]. The Special Purpose Dexterous Manipulator (SPDM) is the third Canadian robotic arm used on the International Space Station (ISS), preceded by the Space Shuttle's Canadamr and the large Canadamr2 [7]. It is an extremely advanced, highly dexterous, dual-armed robot which can carry out delicate maintenance and servicing tasks on the ISS. Robonaut is a humanoid robot designed by the Robotic Systems Technology Branch at NASA's Johnson Space Center. Robonaut can reduce the burden of EVA on astronauts and also serve in rapid response capacities.  
Canadamr2 and Robonaut are all well designed, but they can be considered as too complicated, and are designed only for specific activities, so they cannot work in all of the places outside the space station. There are many operational tasks in space, so the robot needs the ability of moving in a wide range and the ability of precise work. Moreover, the power supply on the space station is limited, so the path planning of the space robot should be power-saving [8; 9].  
Astronauts are weightless and floating in space. Thus, there are hundreds of aluminum handrails and poles on the extravehicular surface of the space station (as shown in Figure 1) for astronauts to get themselves to the expected position during spacewalks and operations. Most importantly, astronauts are fixed by these handrails so that they will not float away.  
A chameleon is a kind of arboreal reptile with a simple physical structure, but can move stably [10]. The conditions of the extravehicular surface are kind of similar to the structure of tree crown. Thus, referring to the simple physical structure and stable motion pattern, a new pattern of a hybrid bionic robot, called the Beijing Astronaut Robot, prototype is design is developed and performance tests are presented in this paper.