Noriyasu Inaba

Dynamics, control and impedance matching for robotic capture of a non-cooperative satellite

In this paper, the contact motion between rigid bodies floating in space is formulated and dynamic conditions are investigated in order to capture a non-cooperative target. As for the theoretical investigation, the definition of the virtual mass is recalled to model the inertial property of a space robot for the case of no joint control. By selecting the posture, the virtual mass can be altered, but its variation may be minor. Then the impedance control is introduced to realize a wide range of impedance characteristics. Impedance matching is discussed for the case in which the hand of an impedance-controlled robot approached and collided with a passive target. The specific inertia property, referred to as Virtual-mass for Impedance Matching, is defined as an equivalent virtual mass of the hand that yields impedance matching with a target floating in space. Experiments are carried out using two robot manipulators as a motion simulator of chaser and target. Through the experiments, the concept of the impedance matching is verified and satellite capture is demonstrated using the strategy that an impedance controlled probe is inserted into the thruster nozzle cone of the target. Whether the impedance matching gives a criteria if the target is pushed away by the probe is investigated.

Rescuing a stranded satellite in space - experimental study of satellite captures using a space manipulator

Space systems have become essential elements providing services of telecommunication, Earth observation and navigation to support our daily lives. With the expanding space activities, more and more space systems have become essential elements providing services of telecommunication, Earth observation and navigation to support our daily lives. With the expanding space activities, more and more satellites are being injected into wrong orbits for their missions and stranded due to failures of rockets. There is a potential need to rescue them by capturing and towing them to the appropriate orbits. Manipulator capture using visual servoing is one of the most promising ways to capture a stranded satellite that does not have a special mechanical interface or a visual marker on it. A study is now being conducted to design a manipulator-based capturing system, taking into account the special aspects of space such as lighting and available computing power. The first results of an experimental study are presented with an explanation of the experimental system in this paper.

A Satellite Simulator and Model Based Operations in Quasi-Zenith Satellite System

This paper introduces a system engineering methodology using a model-based operational concept and satellite simulator as key tools for design, development, and operation processes. The spacecraft model is derived from its required functions. The satellite operational procedures are organized in accordance with operational mode transitions so the operations crew can understand and identify the procedure easily. The model is developed, maintained and used throughout the life cycle of the system. An example of the application of this method is introduced in the development of the Quasi-Zenith Satellite System, which is a Japanese regional satellite based navigation system.

Results of NASDA’s ETS-VII Robot Mission and Its Applications

The rendezvous docking and space robot technologies are indispensable for future space activities such as building and operation of the international space station, inspection and repair of orbiting satellites, and conducting lunar/planetary explorations. Therefore, National Space Development Agency of Japan (NASDA) developed and launched an engineering test satellite named ETS-VII(Engineering Test Satellite #7) on November 28, 1997 to conduct the rendezvous docking and space robot technology experiments. This paper summarizes the ETS-VII mission mainly its robot experiment results and its applications.

Measurement of Satellite Solar Array Panel Vibrations Caused by Thermal Snap and Gas Jet Thruster Firing

Many space satellites have large solar array paddles (Fig. 1) for power generation and large antennas for observation and communication. These large space structures are folded during transport into space by launch vehicles, and deployed after arriving in space. The paddles and antennas must be lightweight because of the payload weight limit of the launch vehicle and are therefore very flexible, with little damping ability. This results in vibrations, which cause serious problems. In particular, there have been increasing demands for enhanced resolution of Earth observations from low Earth orbiting satellites in recent years. Accordingly, the requirements for satellite attitude stability are also increasing. Conversely, it is also known that the attitude stability of low Earth orbiting satellites is disturbed when the satellites go into and leave an eclipse. When the thermal environment around a flexible structure on orbit such as a solar array paddle changes to cold or hot, the flexible structure

Capture and berthing experiment of a massive object using ETS-VII's space robot - World's first on-orbit satellite capture experiment by space robot system

This paper reports results of a capture and berthing experiment of a free-floating massive object in space using an automated space robot system of Japanese ETSVII satellite. The purposes of this experiment are 1) system evaluation of automated capture of massive object and 2) observation of 6 degrees-of-freedom dynamics during capture process while attitude control systems of satellites is turned off. Those results can be reference data for numerical simulations or on-ground test beds for capture and berthing experiments for future onorbit service systems.

Monitoring techniques in a layered control architecture for reliable robotic satellite capture

Satellite capture in space is difficult in a dynamically changing environment. A vision sensor guiding a capturing manipulator toward a satellite can have difficulty recognizing a target covered with shining foil in rapidly changing lighting conditions. Satellite-capturing requires high reliability since space systems are costly. Therefore, it is necessary to be able to detect system limits, to abort a task, or to change a strategy In order to avoid catastrophic failure. Monitoring techniques in a layered-control architecture are proposed for conducting robotic satellite-capturing. The results of ground experiments are also presented.