Precise Telerobotic System for Space Experiment on Ets-vii

In this paper we present the design, development and space test of the world's first precise telerobotic system boarded on an unmanned space vehicle, ETS-VII (Engineering Test Satellite VII). The robotic system has features of skill and autonomy using a three-finger multisensory hand at a work site in space and computer graphicsbased desktop telerobotics at a control site on the ground. We developed a compact robotic system with space environment adaptability and satellite system compatibility as well as dexterity and flexible operability. The robotic system was launched into low-earth orbit in November, 1997. The objectives of the space test are to demonstrate the potential of the multidegree-of-freedom and multisensory hand for use in high-precision in-orbit servicing and to establish telerobotic technology that enables the space robot operation from the ground via a space communications network, overcoming the limitations of communication capacity and time delay. The space test reveals that the system works well in orbit. INTRODUCTION Space robots that perform delicate, complex tasks in unmanned facilities will be indispensable in space activities in the year 2000. One of the key technologies for these robots is a hand with dexterous and flexible capabilities. To date, no such a robotic hand has been developed for space applications. The ROTEX is an intravehicular robot with a 1-DOF (degree-of-freedom) gripper working in the manned Spacelab-D2 module [1]. The small arm of the JEMRMS [2] and SPDM [3] to be aboard the International Space Station will use 1-DOF tools as the end effector. However, they lack dexterity and versatility due to the limited DOF of the end effector. We developed a precise telerobotic system, called ARH (Advanced Robotic Hand System), which performs highprecision tasks on small parts using a three-finger multisensory hand [4],[5]. PRECISE TELEROBOTIC SYSTEM FOR SPACE EXPERIMENT ON ETS-VII Kazuo MACHIDA, Electrotechnical Laboratory, MITI 1.1.4 Umezono, Tsukuba, Ibaraki, 305-8568, Japan Hirotaka NISHIDA, Fujitsu Ltd. Kenzo AKITA, Institute for Unmanned Space Experiment Free-Flyer The technological issues involved in the development of the telerobotic system are to provide skill and autonomy, and to ensure flexible and safe operability from the ground, space environment adaptability, and satellite system compatibility. We resolved these issues and developed a flight model for a space robotic experiment on ETS-VII. The system was launched last year and became the world's first precise EV robot working on an unmanned space vehicle. In this paper we present the design, development and space test of the telerobotic system. First, we deal with the robot mission and system design for use on a satellite. Second, the hand mechanism and multisensory control needed to provide skill and autonomy for high-precision in-orbit servicing are presented. Third, telerobotic control and operation are described. Finally, the initial space test results are presented. SYSTEM DESIGN AND DEVELOPMENT Design Philosophy The main objective of the space test is to prepare the telerobotic technology for high-precision in-orbit servicing. Fig.1 depicts the design strategy for our telerobotic system. First, we consider the requirements for precise in-orbit servicing. One is the high precision working capability for various parts over a wide servicing area. In general, equipment or facilities serviced in space are large, but the objects handled by a robot are small, delicate and various in form for many maintenance tasks. A smallsized precise robot is mounted on a base of macroeffector such as a mobile unit or a large arm. Since the macroeffector lacks positioning accuracy, the precise robot should have fine position compensation and force control functions. Moreover, a hand with multi-DOF mutifingers is required to increase handling versatility. Therefore, skill and autonomy by a hand are important. Another requirement is task execution under an uncertain work environment. Most servicing tasks change the configuration of the work environment with time. Remote measurement of the work environment is necessary to pro-