Shinichi Kimura

A fault-tolerant control algorithm having a decentralized autonomous architecture for space hyper-redundant manipulators

Adaptation to partial failure is one of the most important requirements for space robotics, since space robots cannot be repaired after they have been launched. We propose a decentralized autonomous control algorithm for hyper-redundant manipulators that uses parallel processing with low-performance processors to achieve this adaptation. In this paper, a number of manipulator joints are locked at a certain angle in a computer simulation and the adaptability of the control algorithm to these failures is assessed. The control algorithm successfully continues its positioning task at a rate of more than 90%, even after half of its joints have failed. The control algorithm is also compared with behavior-based control architecture.

Laser beam propagation in ground-to-OICETS laser communication experiments

The first bi-directional laser communication demonstration between an optical ground station and the Optical Inter-orbit Communication Engineering Test Satellite (OICETS) was successfully conducted in March, May, and September, 2006, with an uplink of 2 Mbps and a downlink of 50 Mbps. The optical ground station, located in Koganei, Tokyo, Japan, is operated by the National Institute of Information and Communications Technology (NICT), Japan. Four laser beams were transmitted from the optical ground station to the OICETS satellite in order to reduce the optical signals intensity fluctuation due to atmospheric turbulence. The optical scintillation as a function of the number of beams and the frequency response were measured, and the uplink and downlink laser transmission results were obtained.

Multi CPU control system for kinematic control of a redundant manipulator

Adaptation to partial failure is one of the most important requirements for space robotics, since space robots cannot be repaired after they have been launched. We propose a decentralized autonomous control algorithm for hyper-redundant manipulators that uses parallel processing with low-performance processors to achieve this adaptation. In this paper, a number of manipulator joints are locked at a certain angle in a computer simulation and the adaptability of the control algorithm to these failures is assessed. The control algorithm successfully continues its positioning task at a rate of more than 90 percent, even after half of its joints have failed. The control algorithm is also compared with behavior-based control architecture.

Consensus making of multi-CPU control of hyper-redundant manipulator

A modular manipulator can be reconfigured according to its required function, conditions, and/or partial faults. We propose a control algorithm for a modular redundant manipulator. In this algorithm, local control processors develop independent inverse-kinematic solutions, and determine an overall solution by consensus. In this algorithm, since decisions are not made by a single CPU, but rather through negotiation among the local processors, the control algorithm has no explicit single failure point, which was suggested to be a weak point of our previous control algorithm. Since this new algorithm is also robust against asynchronous operation of the local processors, control performance is enhanced.

An overview of the KODEN experiment between the OICETS satellite and the optical ground station in NICT

SummaryThe KODEN is a first in-orbit laser communication demonstration between a low earth orbit satellite called OICETS/Kirari and an optical ground station at the National Institute of Information and Communications Technology (NICT) in Koganei, Tokyo. Optical links could always be established even under atmospheric turbulence when partly clear skies were predominant in March, May, and September, 2006. The uplink and downlink bit error ratios were measured to be 10−7–10−3. This achievement is a milestone for future high-data-rate satellite communications.ZusammenfassungDas Akronym KODEN steht für die erste erfolgreiche Demonstration eines Laserkommunikationsexperiments zwischen dem Satelliten OICETS/Kirari in erdnaher Umlaufbahn (LEO) und der optischen Bodenstation des staatlichen Institutes für Information und Kommunikation (NICT) in Koganei, Tokio. Trotz atmosphärischer Turbulenzen konnte die optische Verbindung stets hergestellt werden, unter vorwiegend wolkenfreiem Himmel in den Monaten März, Mai und September 2006. Die Fehlerbitraten der beiden Kommunikationskanäle lag zwischen 10−7–10−3. Das Experiment stellt einen Meilenstein in der Entwicklung zukünftiger Satellitenkommunikationssyteme mit hohen Datenraten dar.

Evaluation of audio feedback system for Engineering Test Satellite VII

We have developed an audio interface system for the efficient operation of ETS-VII. Unlike a visual interface, this audio interface allows the operator: to observe information even if he is not focusing on it, and to easily identify trends and changes. The system analyzes telemetry information in real-time, and converts changes in the status of information into voice data, and changes in the magnitude of forces into motor noise frequency. The effectiveness of this audio interface was verified in ETS-VII operations by monitoring eye movements over time. Time is measured by the mean interval between status changes and command sub-missions. An eye-mark recorder records eye movements. With the audio interface, the operator has sojourned time to see graphic simulator/down link images. Without audio interface, the operator have sojourned to see telemetry display. Our data suggests that when using the audio interface the operator spends much less time looking at the display.