The Communications Research Laboratory plans to test an antenna-assembling mechanism on the Engineering Test Satellite 7. The test is one of the application missions for the space robotics experiments that will be conducted mainly by the National Space Development Agency of Japan (NASDA). The purpose of the test is to verify the ability of the antenna assembling mechanism to function in space and to experiment on the teleoperation of a space robot to develop antenna-assembling technology. We present the test experiment plans and the outline of the onboard assembling mechanism

Kimura, Shinichi

Morikawa, Hajime

Nakamura, Kazuo

Suzuki, Yoshiaki

Takahashi, Tetsuo

English

NASA Technical Reports Server

Antenna-Assembling Mechanism Test on ETS-VII N95- 23727
Yoshiaki Suzuki, Shinichi Kimura, Tetsuo Takahashi,
Communications Research Laboratory
4-2-1, Nukui-Kitamachi, Koganei-shi,
Tokyo 184, Japan
Tel 81 423 27 7512 Fax 81 423 24 8966
E-Mail Address ryo@crl.go.jp
Kazuo Nakamura, and Hajime Morikawa
NEC Corporation
4035, Ikebe-cho, Midori-ku,
Yokohama 226, Japan
KEY WORDS AND PHRASES
Engineering test satellite, large space antenna,
antenna assembling, teleoperation, tele-
robotics
ABSTRACT
The Communications Research Laboratory
plans to test an antenna-assembling
mechanism on the Engineering Test Satellite
VII. The test is one of the application
missions for the space robotics experiments
that will be conducted mainly by the National
Space Development Agency of Japan
(NASDA). The purpose of the test is to
verify the ability of the antenna assembling
mechanism to function in space and to
experiment on the teleoperation of a space
robot to develop antenna-assembling
technology. In this paper, we present the test
experiment plans and the outline of the
onboard assembling mechanism.
INTRODUCTION
Assembling antennas by means of a robot
is one method to build large-scale dish-type
space antennas for high frequency
applications. Assembling-type antennas have
possible advantages over deployable-type
antennas to achieve highly accurate reflector-
surface construction and is appropriate for
high-frequency applications. [1] The
Communications Research Laboratory (CRL)
planned the antenna-assembling experiment
on the Japanese Experimental Module (JEM)
of Space Station and started developing
assembling-type antennas in 1986. At first,
we developed the assembling mechanism
which couples the center panel with the
divided peripheral panels. The mechanism is a
key component for assembling antennas easily
in space. A smart mechanism makes antenna
construction possible using a robot arm
instead of Extra Vehicular Activity (EVA).
Two antenna scale models with different types
of mechanisms are developed [2] and tested
first on the ground using a robot arm. Before
the experiment on JEM, we planned a
precursor experiment to test the mechanism on
the Engineering Test Satellite-VII (ETS-VII)
[3], which will be launched in 1997. The
purposes of the test on the ETS-VII are to
verify the ability of the assembling
mechanism to function in space and to
experiment on the teleoperations of a space
robot to develop antenna assembling
technology.
ASSEMBLING-TYPE ANTENNA
279
https://ntrs.nasa.gov/search.jsp?R=19950017307 2020-06-16T08:44:08+00:00Z
Figure 1 shows the configuration of the
assembling-type antenna. The main reflector
is divided into 8 peripheral panels and a center
panel. A sub-reflector is attached to the center
panel with four stays. The assembling
mechanism is used to couple the center panel
and the divided peripheral panel, as shown in
the figure.
In the JEM experiment, construction of a
2- to 5-meter diameter antenna is planned as
the first step. Initially, the center part
attached behind the center panel, which
contains RF compartment and pointing
equipment, will be assembled on the exposed
facility of the JEM. Next, divided panels will
be attached to the center panel, one by one, by
using the Japanese Remote Manipulator
System (JRMS).
EXPERIMENTAL SYSTEM FOR ETS-VII
CRL plans to test the antenna-assembling
mechanism on the Engineering Test Satellite
VII (ETS-VII). In this experiment, only the
assembling mechanism is to be tested because
it is the key component of the assembling-type
antenna. Testing the assembly performance
under various conditions (described later) as
well as its durability in space is an important
objective of the experiment.
Another objective is testing the
teleoperation technology under the effects of
communication delay and the limited
communication capacity caused by the long
distance from the operator on earth to the
assembly site in space.
Figure 2 shows the experimental system
block diagram including the onboard system
and the earth control system. CRL will
develop hatched equipment: an onboard
antenna-assembling mechanism and a ground
auxiliary teleoperation system for the
experiment.
Assembling Mechanism
The antenna-assembling mechanism is
composed of a fixed part (FP) which contains
the mechanism for the center panel and a
coupling part (CP) which contains the
mechanism for the divided panel as shown in
Fig. 3. The FP is attached to the satellite main
body structure. The coupling mechanism used
is a rotary hook-type latch actuated by a
spring force (Fig. 4).
To make the assembly procedure easy and
secure, we introduced both a mechanical
guide system and a visual guide system. The
mechanical guide system consists of a guide
cone and a cone receptacle which
mechanically compensates for the positioning
error in the assembling process. The visual
guide system uses a three-dimensional target
mark (Fig. 5) attached to the FP and a hand
camera system attached near the robot hand.
The image of the target is transmitted to the
ground control system and is used to
determine the relative position and attitude of
the CP to the FP. This information is used to
teleoperate the onboard robot arm. The
compliance mechanism in Fig. 3 is introduced
to absorb the possible reaction force induced
by the mechanical contact of the FP and the
CP.
Teleoperation System
The teleoperation equipment consists of a
workstation and an image processor, and
functions as the robot arm control, image
processor and robot operation simulator.
Teleoperation commands generated in the
equipment are transmitted to the satellite via
NASDA's satellite control facility.
Figure 6 shows the block diagram of CRL's
teleoperation equipment. The basic system
consists of a teleoperation computer, an image
processor, a video processor, and a monitor.
The teleoperation computer is used for arm
control calculations and data communication.
The video processor is used for processing the
target-mark image. The image processor is
280
used for overlaying the camera image on the
CRT.
The teleoperation auxiliary computer is
used only for the predictive bilateral control
experiment described later.
The basic system software consists of a
teleoperation manager, a simulation module, a
visual simulation module, and an interface
module. Each module works as an
independent parallel process. The
teleoperation manager communicates with
other modules and exchanges parameters and
data. Almost all operations such as the menu
selection, parameter change, and command
transmission, can be done by using a mouse
on a graphical user interface (GUI).
The teleoperation manager functions are
*robot teleoperation,
*data management, and
*controlling other modules.
The simulation module functions are
*robot movement simulation
*3-D wire frame simulation-image
display of the robot and the assembling
mechanism, and
*pre-operation check.
The visual simulation module functions are
*image processor control, and
*video processor control.
The data which will be acquired from the
experiment are
*torque and force data of the arm,
*position of the arm (angle of the joints),
*video image of the CCD camera,
*target position calculated from the video
image, and
*operation duration time.
TEST EXPERIMENT PLAN
Several kinds of assembling and
disassembling experiments are planned:
Basic Assembly and Disassembly
Experiment
Repeating the assembly and disassembly
operation while changing the following
parameters:
* Operation mode of the arm
(teaching/manual mode)
* Operational speed of the arm
* Insertion force of the coupling
* Control mode of the arm (position
control/force control mode)
Allowable Positioning Error
The FP and the CP can be assembled
even with a certain positioning error using
the mechanical guide cone. In this
experiment, the allowable positioning error
is measured.
Assembling and Disassembling with
Intentional Disturbance
Sine-wave/random positioning error will
be added to the robot command to simulate
the assembly using a long-armed
manipulator with excess vibration.
Fully-Automatic Assembling Experiment
The relative position of the FP and the
CP is calculated using visual feedback of
the target mark images. The position data
enables automatic assembly of the FP and
the CP.
Predictive Bilateral Control
A virtual model of the operation target
is constructed in real-time. The virtual
image and the reaction force calculated
from the model is supplied to the operator
who controls the master arm while
watching the virtual image with the
superimposed real image delayed by the
distance.
CONCLUSION
The plans of the assembling mechanism
test on ETS-VII and the outline of the onboard
281
mechanism is presented in this paper. The
experiment will demonstrate the possibility of
constructing large-scale dish-type antennas
using a space robot controlled by a ground
operator. The actual antenna construction in
space with this type of assembling mechanism
is planned for the space station using JEM's
remote manipulator system.
The onboard mechanism for the ETS-
VII is now under the critical-design stage and
a BBM is under construction. Before the ETS-
VII experiment, a ground simulation test using
the BBM and the NASDA's test bed system
will be done.
ACKNOWLEDGEMENTS
We would like to thank the members of
ETS-VII group in NASDA for their great
effort and help in including our mission on the
ETS-VII Project.
REFERENCES
[1] T. Iida, K. Okamoto, Y. Ohkami, S. Kibe,
H. Koshiishi, M. Naka, and H. Yamamoto, :
"A Space Station Experiment on Large
Antenna Assembly and Measurement," Acta
Astronautica Vol.12. No. 5, pp.335-344, 1985.
[2] Y. Suzuki, T. Takahashi, M. Tanaka, T.
lida, S. Yokota, and K. Ohshima, : "Scale
Model Development of Assembling Type
Space Antenna," 42nd Congress of the
International Astronautical Federation, IAF-
91-314, October 5-11, 1991, Montreal,
Canada.
[3] M. Oda, Y. Wakabayashi, S. Ichikawa, R.
Imai, and T. Anzai, : "ETS-VII, The World
First Telerobotic Satellite (Mission and Its
Design Concept)," Artificial Intelligence,
Robotics and Automation, in space,
Toulouse, September 92, pp307-318.
Stay
Center
panel
-__/Subreflector
_ / Antenna Assembling
_._ Mechanism
,
/ivided panel
Fig. 1 Assembling-type antenna and assembling
mechanism.
282
Stn. _ Image DataCOMETS Earth
/
Teleoperation CMD
CCSDS Processor
Mission TLM
1
ETS-VII Satellite I TLM/CMD
System Operation I
Tracking & Control Interface
Camera
Robot Experiment __J
Onboard Computer |
I I ETS-VII
[ Communication/Data Processing I Onboard System
[
Image
Processor
Teleoperation
Contro
Support
Computer
NASDA's Operation
System
I
Part developed by CRL
Fig. 2 ETS-VII robotics experiment system block diagram.
ETS-VII onboard
Manipu_
/
Camera
Compliance
Mechanism
Coupling Part (CP)
Guide Cone
Latch Mechanism
Guide Cone
Latch Pin _. Receptacle
_'_ Part
(FP)
Fig. 30nboard antenna-assembling mechanism
283
t ' ' _ ' E" "_'cH_,
Ill . If _ _ _( /-'_ \
t i _::r _ ""-- '--_-_-_-_-_-_-_-___ _
Torque supplied from
Rotary Hook 1- Jrobot arm
 ,atS.
_ :_i"" : ' SAhs°Corkber
,___fl _ Latch Pin
Fig. 4 Structure of the latch mechanism.
Reference Mark Cross Section
Ring Mark Center Mark
Fig. 5 Target mark for the visual guide
284


Antenna-assembling mechanism test on ETS-7

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