REX-J, Robot Experiment on the ISS/JEM to demonstrate the Astrobot’s locomotion capability Mitsushige Oda1), Masahiro Yoshii1), Hiroki Kato1), Atsushi Ueta1), Satoshi Suzuki2), Yusuke Hagiwara3), Taihei Ueno3) 1) Aerospace Research and Development Directorate, Japan Aerospace Exploration Agency, Ibaraki, Japan 2) AES Co. Ltd.., Ibaraki, Japan 3) Department of Mechanical and Aerospace Engineering, Tokyo Institute of Technology, Tokyo, Japan A unique space robot named Astrobot (Astronaut + Robot) is being developed and will soon be demonstrated on the International Space Station, Japanese experiment module KIBO. Tasks of the robot will include supporting astronauts’ works in space and working instead of astronauts. To work with or instead of an astronaut, the robot needs to be able to moves around / inside the space facility, e.g. a space station and need to conduct tasks like an astronauts. The Astrobot’s locomotion capability is realized by an extendable robot arm and tethers. Tethers will be anchored to a handrail or other suitable anchoring points using an extendable robot arm. This unique mechanism of the proposed robot makes it possible to realize the robot in a small volume while the robot can move around the wide area. In order to demonstrate usefulness of this unique robot, an onboard experiment on the exposed facility of the International Space Station Japanese Experiment Module, “KIBO” will be conducted in the year 2012. Development of the experiment system is progressing now. Key Words: International space station, Astronaut, Space robot, STEM, Astrobot 1. Introduction exploring the moon and the planetary surfaces. Construction of the International Space Station However those robots are not good at helping Japanese Experiment Module, KIBO is now completed astronauts’ IVA (Intra vehicular activities) and and full utilization of KIBO for development of new EVA (Extra vehicular activities). Therefore, technologies for future space missions and improving space robots of a new type are necessary to reduce knowledge and life of people on the Earth. JAXA is now the workload of astronauts. This paper presents a implementing various missions to utilize KIBO. JAXA is new type of space robot, Astronaut Support-Robot to conduct a space robot experiment on the international (Astrobot), that can move inside and outside the space station Japanese experiment module (ISS/JEM). space station and which can conduct tasks that The experiment is named as REXJ (Robot Experiment on are currently conducted by astronauts. JEM). Aim of the REXJ experiment is to demonstrate capability of a new type of space robot named Astrobot (Astronaut + Robot). There are many tasks on the space station to be conducted by astronauts. Some tasks are simple but need many hours. Some tasks are dangerous to conducts. Some tasks need extensive skills. However, number of astronauts onboard the space station is limited. Therefore, from interests of safety and economy, some tasks should be conducted by robots and some tasks should be conducted by astronauts. Robots are also welcomed to assist astronauts while they conduct some tasks. The Astrobot is a type of space robot that will support the astronaut by assisting astronaut’s work or conducting works instead of astronauts. The Astrobot is a new type space robot beyond the orbital robots and the lunar / Fig.1. Astronaut conducting Extra-Vehicular Activity planetary exploration robots. The space shuttle remote manipulator system and the space station’s remote 2. Tasks of astrobot manipulator system are typical examples of the orbital Interviews with astronauts were conducted to robots. The pass finder and the Mars Exploration Rovers determine the actual needs and requirements for are typical examples of the exploration robots. the Astrobot. Those interviews revealed the The above orbital robots and the exploration following. robots are good at handling massive payload and x Astronauts are eager to accomplish assigned 1 i-SAIRAS 2010 August 29-September 1, 2010, Sapporo, Japan 567 missions. to move around the space facilities such as the x Astronauts are busy in space. For that reason, space station. Each method has advantage and they want to use their limited time in space disadvantages. efficiently. x Astronauts are burdened with many tasks. Method Example Advantage / Some tasks, such as EVA, are very important; Disadvantage astronauts are eager to accomplish them. Free Flying AERCam Risk of collision, limited x Many preparatory tasks must be accomplished, life by the fuel consumption e.g. transporting equipment to the EVA work Attached to a Dextre Limited locomotion area site to do EVA tasks such as installing large RMS by the reach of RMS equipment or repairing the facility Move on rails SSRMS Locomotion area is x Some tasks such as monitoring equipment and limited by the reach of facility inspection are time-consuming, RMS and rails although they are simple to conduct. Inchworm SSRMS Locomotion area is motion using limited by the location These findings suggest that a support-robot grapple of the grapple fixture should be designed to conduct at least the fixture following tasks. Multi arms EUROBOT, System becomes x Simple but time-consuming tasks: Such tasks robot that can Robonaut complex since number of grasps degrees of freedom include monitoring equipment, inspection of handrails increase. outer surfaces of the space station (inspection Move by Charlotte Size of robot is small of impact damage by debris), and monitoring tethers while locomotion area is of astronauts’ activities. wide x Transporting equipment: conveying and Table 1. Ways of robots’ locomotion in space receiving equipment to and from the astronaut. In the future, robot(s) will also build and Since most of locomotion methods have limited maintain large space facilities such as the locomotion area while their systems are solar power satellite. To build the solar power complicated, we decided to use tethers to move a satellite economically, robots, not astronauts, robot around the space station. Tethers will be should be used to build the facility. connected to handrails that are originally prepared to be used by astronauts to support their 3. REXJ mission body. On the international space station, there are REXJ is an acronym of the Robot Experiment on many handrails are attached at an interval of one the Japanese experiment module of the ISS. meter or so. Astronaut grasps this handrail when they work outside the space station. (See Fig,1.) 3.1 Objective of REXJ mission Purpose of the REXJ is to demonstrate some key 3.3 Astrobots’ locomotion principle technologies to realize the Astrobot. Technologies Since already proposed space robot’s locomotion to be demonstrated by the REXJ mission include methods have critical disadvantage, we decided to following capabilities. use the tethers to move the robot around the space x Astrobot’s capability to move around the station as follows. Figure 2 depicts the principle of space station and other space structures the robot’s locomotion; using infrastructure prepared for the astronaut’s work. x Astrobot’s capability to manipulate equipment or tools designed for astronauts. 3.2 Astrobot’s locomotion capability Astrobots must be able to move around the space structures such as the space station like an astronaut. If a robot needs some special equipment on the space station and those are not included in the current space station, then such special equipments will not be attached unless those are highly required. Then the robot cannot Fig. 2 Principle of Robot Locomotion move around. There are several ways of locomotion as follows (1) The robot has several tethers inside the robot 2 568 body. Tethers are wound in reels. Each tether Most robot hands developed for on-ground has a hook-like mechanism to attach the commercial applications do not satisfy this requirement. tether to a structure, such as a handrail, They have very limited grasping power because of the which is prepared for astronauts. actuators’ capability to drive fingers. Most hands include (2) Robots have an extendable robot arm. The rotary actuators in the finger joints, but humans’ hands robot arm has a robot hand at its end. are too small to contain sufficiently powerful actuators. (3) The extendable robot arm will grasp the tether Most powerful robot hands are gripper-type robot hands, but those hands are insufficiently dexterous to do many hook and extend the tether. 4) (4) It attaches the tether hook to a handrail or tasks. Two famous robot hands, the Stanford-JPL hand and the Utah/MIT hand5) developed in the 1980s, had secures itself by some other method. large actuators inside of the robot’s body to increase (5) Retract the robot arm and grasp the other grasping power, but the actuators made the hand tether hook. impossible to use depending on the situation and payload. (6) Connect other tethers to other points. Furthermore, this method complicates mechanisms and (7) Adjust the length of each tether. Then the maintenance. location of the robot will change. These analyses indicate that a robot hand for (8) The area in which the robot can move depends Astrobots should have the following functions. on the number of tethers attached to the (a) The robot hand must have sufficient dexterity to structure and the location of each tether grasp or handle payloads with high grasping power; anchoring point. Using three tethers, the area it should be small to be installed in many arms and in which the robot can move is a triangular must be able to handle objects a human could usually plane made by three tether-anchoring points. handle. The area in which the robot can move becomes (b) The robot hand should be removable or exchangeable a three-dimensional space if the number of from its wrist so that it can be maintained easily or tether-anchoring points is four or greater.