This paper reports experiments involving the handling of flexible parts (e.g. wires) when using a teleoperated system with time delay. The task is principally a peg-in-hole task involving the wrapping of a wire around two posts on the task-board. It is difficult to estimate the effects of the flexible parts; therefore, on-line teleoperation is indispensable for this class of unpredictable task. We first propose a teleoperation system based on the predictive image display, then describe an experimental teleoperation testbed with a four second transmission time delay. Finally, we report on wire handling operations that were performed to evaluate the performance of this system. Those experiments will contribute to future advanced experiments for the MITI ETS-7 mission

Asakura, M.

Bamba, H.

Komoriya, K.

Kotoku, T.

Matsuhira, N.

Takamune, K.

Tanie, K.

English

NASA Technical Reports Server

Manipulating Flexible Parts Using a Teleoperated System
with Time Delay: An Experiment N95- 23729
T.Kotoku, K.Takamune, K.Komoriya and K.Tanie
Mechanical Engineering Laboratory, AIST-MITI.
1-2 Namiki, Tsukuba, Ibaraki 305 Japan
Tel: +81-298-58-7284, Fax: +81-298-58-7201
E-mail: toku@mel.go.jp
N.Matsuhira, M.Asakura and H.Bamba
R & D Center, Toshiba Corporation
4-1 Ukishima, Kawasaki, Kanagawa 210 Japan
Tel: +81-44-288-8026, Fax: +81-44-288-8210
E-mail: 000091050512@tg-mail.toshiba.co.jp
KEY WORDS AND PHRASES
Engineering test satellite VII (ETS-VII),
Flexible parts handling, Predictive display,
Teleoperation, Time delay problem.
ABSTRACT
This paper reports experiments involving the
handling of flexible parts (e.g. wires) when
using a teleoperated system with time delay. The
task is principally a peg-in-hole task involving
the wrapping of a wire around two posts on the
task-board. It is difficult to estimate the effects
of the flexible parts, therefore, on-line tele-
operation is indispensable for this class of unpre-
dictable task.
We first propose a teleoperation system based
on the predictive image display, then describe an
experimental teleoperation testbed with a four-
second transmission time delay. Finally, we
report on wire handling operations that were
performed to evaluate the performance of this
system. Those experiments will contribute to
future advanced experiments for the M1TI ETS-VII
mission.
INTRODUCTION
Remote manipulation in outer space from the
ground is one of the most important technologies
for assisting outer space activities such as the
construction and maintenance of space stations,
and the operation of space laboratories. The long
distances between the ground command station
and outer space robots incur an inevitable time
delay of communications between these two
systems; there are many research activities being
conducted on this time delay problem.
Several ideas have been proposed: local intel-
ligence with sensory feedback [ 1], a predictive
image display system which superimposes a
phantom robot with no delay on the remote
camera image [2], a teleoperation system using
force-reflecting simulator [3,4] and a tele-
programming system which issues program
segments to the remote site [5]. Space robot ex-
periments have also been carried out on a space-
lab mission [6].
In this paper we consider the tasks involved
in handling flexible parts by a teleoperated
system with communication delays, and focus on
a wire handling task as an example of a general
unpredictable task for teleoperation.
This task is complicated for two reasons: 1)
the dependence of the generated path on the
changes of the shape of the flexible component,
and 2) the difficulty of estimating the forces
generated by the deformation of the flexible part.
It is difficult to estimate the effects of the wire,
and pre-programmed methods are not suitable
for this class of task; an on-line teleoperation
system is indispensable.
We first propose a teleoperation system based on
a predictive computer graphics display, then
describe an experimental teleoperation testbed
with a four-second communication time delay.
Finally, we report on wire handling operations
that were performed to evaluate the effectiveness
of the system.
TELE-OPERATION SYSTEM BASED
ON PREDICTIVE CG DISPLAY
In this section, we propose a remote manipu-
lation system based on the predictive image
display technique. Figure 1 shows the block
structure of this system. The system consists of
the master operating station subsystem and the
289
https://ntrs.nasa.gov/search.jsp?R=19950017309 2020-06-16T08:44:04+00:00Z
Master ] _
Handle [/'c
System I
GraphicLgJ
Display I -
delay
Master Operating Station Slave Arm System
Figure 1. The proposed master-slave tele-operation system
slave arm subsystem, and these two are con-
nected by a low-bandwidth communication line
with a large time delay.
If we assume a several-second-delay, we are
not able to use the conventional master-slave
system which consists of a large control loop, so
we adopt the predictive graphic image display
technique.
The master subsystem is composed of a
master handle, its controller, and a graphic simu-
lator. This master subsystem simulates a virtual
arm and displays it as a three-dimensional image.
In this simulator, we ignore interactions with the
environment and the hardware limitation of the
slave system, hence the operator can control the
virtual arm on the graphic display freely through
the master handle. The series of configurations
(position / orientation) of the virtual arm during
operation are transmitted to the slave arm con-
troller as a command configuration Pc.
The slave arm subsystem is composed of a
slave arm and its double-loop controller which
prevents the slave arm from excess loads. In the
outer position loop, the operational force com-
mand Fc for the inner loop is given by
-F_it
Fc = ] Flimit
[K(ec- ?)
(in case K (Pc - P) < -Fr_i_ )
(in case K(P c - P) > F_it) (1)
(others)
where Fli,,u't is the limit force/torque to prevent
the slave arm from applying excess loads, K is
the gain parameter of the outer position loop, and
Pc and P are the commanded and the sensed
configurations of the slave arm, respectively.
We assume a position-controlled slave arm.
In the inner force control loop, the reference
position Pr for the slave arm is calculated by
using a nominal model of the slave arm. Its
transfer function is as follows,
1
P,(s) = (F_(s)- F(s)) (2)
s(rns + b)
where F is the sensed force at the tip of the slave
arm, and m and b are the inertia and the damping
parameters respectively of the nominal model.
These parameters are designed to keep the
bandwidth of the output reference position Pr
within the bandwidth of the slave arm.
The operator manipulates the virtual arm on
the graphic display using the master handle,
sometimes watching the monitor of the slave ann
system to check the motion of the slave ann for
any failure of the wire-wrapping task. In the
event of any such failure, the operator returns the
virtual arm to its previous state and retries the
wire wrapping.
EXPERIMENTAL TELEOPERATION
TESTBED
To confirm the function of the proposed
system, we constructed a teleoperation testbed
with a four-second time delay. Figure 2 shows
an overview of this experimental setup. The
sequence of the command positions from the
master subsystem is stored once in a ring buffer
program which simulates a four-second com-
munication time delay. The response of the slave
ann is thus delayed by four seconds.
An IRIS workstation (Crimson/Reality-
Engine) is used for the three dimensional
computer graphic display, and a newly designed
hybrid master system (Fig. 3) is used for the
master handle. This handle has three degrees of
orientational freedom, and the orientation of the
virtual arm follows the orientation of this master
290
Slave Robot
Board i
Figure 2. Overview of the experimental setup
handle. A six-axis force/torque sensor is
installed at the base part of this handle, and the
translational velocity of the virtual arm is propor-
tional to the force which is applied by the
operator.
Two monitor displays are used for the master
operating station, one to display the computer
graphics which simulate the virtual arm, and the
other to display the delayed camera image of the
slave arm system. On the graphic display, the
front view of the task board with two holes and
two poles, and the manipulated peg, are
displayed as 3D solid models.
To check the real motion of the slave arm, the
information of the real peg is also displayed
super-imposed on this window as a 3D wire-
frame model. On the top-right corner of the
graphic display, a small window displays a side
view of the slave ann system. On the top-left
corner of the graphic display, another small
window displays the force information of the
slave arm.
A direct-drive arm with six degrees of
freedom is used for the slave ann. At the tip of
this arm, a six-axis force / torque sensor is
installed to detect the forces generated by the in-
teraction with the environment. A slave arm
control algorithm described before is imple-
mented on a parallel processing system of trans-
puters. The force limit Flimi t was set to 5N to
protect the slave arm from excess loads during
operation.
WIRE HANDLING TASK
As an example task of manipulating flexible
parts, we tested a wire handling operation. We
used a simple task-board with two holes, two
poles and one manipulated peg with a thin copper
cable. The clearance between the peg and the
hole is 0.035mm.
The task is principally a peg-in-hole task in-
volving wrapping a wire around two posts on the
task-board. The task consists of three stages;
first, extracting the peg from the hole, second,
wrapping the wire around the two poles, and
third, inserting the peg into the initial hole.
The results of the experiments are shown in
Fig. 4 as a sequence of wire handling operations.
Despite of the large communication time delay in
this teleoperation system, we confirmed the
success of the wire handling operation.
To maintain consistency between the virtual
arm space and the real slave arm space, we cali-
brated the system prior to the experiments.
CONCLUSION
In this paper, we investigated a wire handling
task as an example of an unpredictable task. We
proposed a teleoperation system with the predic-
tive image display and the double-loop slave
controller, constructed a master-slave teleopera-
tion testbed, and performed the wire handling
task with a four-second communication delay.
- L__ l l._ -'5-- I -
..... I
i
Figure 3. Structure of the hybrid master handle
291
MITI is planning to participate in the space
robotic experiment on the ETS-VII [7], and an
advanced robotic hand (ARH) with multiple
degrees of freedom and sensors has been devel-
oped for this mission [8]. This experiment will
contribute to future advanced experiments for the
MITI ETS-VII mission.
This research was performed as a joint
research project between the Mechanical
Engineering Laboratory and the Research and
Development Center of Toshiba Corporation.
Acknowledgments
The authors would like to thank Dr. K.
Machida, ETL, for his valuable suggestions and
discussions on this joint research project.
REFERENCES
[1] Sheridan, T., 1992. Telerobotics, automation, and
human supervisory control, MIT Press.
[2] Bejczy, A. K.; and Kim,W. S., 1990. Predictive
displays and shared compliance control for time-delayed
telemanipulation. In Proc. of the IEEE Int. Workshop on
Intelligent Robots and Systems (IROS'90), 407-412.
[3] Kotoku, T.; Tanie, K.; and Fujikawa, A., 1990.
Force-reflecting bilateral master-slave teleoperation
system in virtual environment. In Proc. of the Inter.
Symp. on Artificial l_telligence, Robotics and
Automation in Space (i-SAIRAS'90), 295-298.
[4] Kotoku, T., 1992. A predictive display with force
feedback and its application to remote manipulation
system with transmission time delay. In Proc. of the
IEEE/RSJ Int. Conf. on Intelligent Robots and Systems
(IROS'92), 239-246.
[5] Funda, J.; Lindsay, T. S.; and Paul, R. P., 1992.
Teleprogramming: towards delay-invariant remote ma-
nipulation. Presence 1(1): 29-44.
[6] Brunner, B.; Hirzinger, G.; Landzettel K.; and
Heindl, J., 1993. Multisensory shared autonomy and tele-
sensor-programming -- key issues in the space robot
technology experiment ROTEX. In Proc. of the
IEEE/RSJ Inter. Conf. on Intelligent Robots and Systems
(IROS'93), 2213-2139.
[7]Oda, M.; Wakabayashi, Y.; Ichikawa, S.; Imai R.;
and Anzai, T., 1992. ETS-VII, the world first telerobotic
satellite (mission and its design concept), In Proc. of the
Inter. Syrup. on Artificial Intelligence, Robotics and
Automation in Space (i-SAIRAS'92), 307-318.
[8] Machida K.; and Ono, S., 1992. Space experiment
plan of advanced robotic hand for ETS-VII, In Proc. of the
Inter. Syrup. on Artificial Intelligence, Robotics and
Automation in Space (i-SAIRAS'92), 219-223.
Figure 4. Task sequence of a wire handling
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Manipulating flexible parts using a teleoperated system with time delay: An experiment

Manipulating flexible parts using a teleoperated system with time delay: An experiment

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