The development of the Space Station Freedom tasks that are compatible with both telerobotic as well as extravehicular activity is a necessary redundancy in order to insure successful day to day operation. One task to be routinely performed aboard Freedom will be the changeout of various quick disconnect fluid connectors. In an attempt to resolve these potentially contradictory issues of compatibility, mock-ups of couplings suitable to both extravehicular as well as telerobotic activity were designed and built. An evaluation performed at the Remote Operator Interaction Laboratory at NASA's Johnson Space Center is discussed, which assessed the prototype couplings as well as three standard coupling designs. Data collected during manual and telerobotic manipulation of the couplings indicated that the custom coupling was in fact shown to be faster to operate and generally preferred over the standard coupling designs

Bierschwale, John M.

Fleming, Terence F.

Sampaio, Carlos E.

Stuart, Mark A.

English

NASA Technical Reports Server

N91-20664
SPACE STATION FREEDOM COUPLING TASKS:
AN EVALUATION OF THEIR SPACE OPERATIONAL COMPATIBILITY
Carlos E. Sampaio, John M. Bierschwale,
Terence F. Fleming, and Mark A. Stuart
Lockheed Engineering and Sciences Company
Houston, Texas
ABSTRACT
The development of Space Station Freedom tasks
that are compatible with both telerobotic as well as
extravehicular activity is a necessary redundancy in
order to insure successful day to day operation.
One task to be routinely performed aboard
Freedom will be the changeout of various quick dis-
connect fluid connectors. In an attempt to resolve
these potentially contradictory issues of compatibil-
ity, mock-ups of couplings suitable to both extra-
vehicular as well as telerobotic activity have been
designed and built. This paper discusses an evalua-
tion performed at the Remote Operator Interaction
Laboratory at NASA's Johnson Space Center which
assessed the prototype coupling as well as three
standard coupling designs. Data collected during
manual and telerobotic manipulation of the cou-
plings indicated that the custom coupling was in fact
shown to be faster to operate and generally
preferred over the standard coupling designs.
INTRODUCTION
After its completion, Space Station Freedom will
continue to require a great deal of maintenance and
support work in order to maintain daily operations.
Dextrous manipulators including the Flight
Telerobotic Servicer, the Special Purpose Dextrous
Manipulator, and the Japanese Experimental
Module Fine ann will not only be critical to the per-
formance of these tasks but may actually be the
primary system devoted to the execution of many of
them.
Among the tasks to be commonly performed will be
the coupling and uncoupling of fluid connectors
designed to provide remote resupply of liquids and
gases in orbit (NASA, 1989). This will be done
using various quick disconnect (QD) couplings
designed to mate and demate repeatedly without
leakage. At present, several designs exist which al-
low the couplings to be quickly mated and demated
by an extravehicular astronaut. While it is critical
that these couplings be capable of manipulation by
the suited astronaut, it is equally critical that these
couplings be capable of successful operation with a
telerobotic manipulator in order to reduce the like-
lihood of these hazardous extravehicular operations
in the first place. Consequently, these couplings
necessitate a design that is compatible with both
modes of operation.
QD coupling designs and methods of actuation can
vary widely. The coupling's contents, the amount
of pressure it will have to sustain, the amount of
flow it will need to accommodate, as well as several
other factors all have a bearing on the coupling's
final form. Clearly aboard Freedom, the varying
conditions under which the different QDs operate
will necessitate that their designs be different as
well. Just as clear, however, is the concern that a
proliferance of coupling designs will, at best, often
result in uncertainty in a coupling's operation when
encountered, and at worst, result in unsuccessful
mating or even loss of fluid or pressure as a result
of implementing the incorrect coupling process.
Although the size and action of the couplings will
obviously need to vary, it is preferable that a similar
operation concept be shared over the coupling
points aboard Freedom in order to reduce the like-
lihood of using the incorrect procedure.
It is widely held that in the vast majority of cases, a
task that has been designed to be telerobotically
compatible will be compatible with the extravehicu-
lar astronaut as well (Newport, 1989). This study,
conducted in the Remote Operator Interaction
Laboratory (ROIL) at NASA's Johnson Space
Center (JSC), evaluated subjects' abilities to mate
and demate QD couplings of varying design both
telerobotically as well as manually. In a previous
179
https://ntrs.nasa.gov/search.jsp?R=19910011351 2020-03-19T19:06:46+00:00Z
study assessing various telerobotic control modes, a
manual condition was included as a representation
of the optimal performance to strive for in the de-
sign of a space glove (Hannaford,1989). Therefore,
the manual condition in this study is similarly in-
cluded as a baseline to reasonably approximate
extravehicular activity (EVA).
In collaboration with various telerobotic interface
development facilities including the ROIL,
Symetrics Inc. has been iteratively designing fluid
couplings whose operation is intended to be tele-
robotically as well as EVA compatible. One of
these iteratively designed couplings was among the
four coupling designs evaluated in this investiga-
tion. Thus the hypothesis of this study proposes that
the coupling designed to be telerobotically and EVA
compatible will be mated and demated the most
quickly and be most preferred subjectively for both
the telerobotic as well as manual conditions.
METHOD
Subjects. Four subjects participated voluntarily in
this study. In order to minimize learning effects as-
sociated with the various systems involved, all sub-
jects had extensive experience with the telerobotic
and viewing systems employed in the study. None
of the subjects had any experience operating the QD
couplings prior to their participation.
Apparatus. Three equipment systems were em-
ployed in the ROIL. These are: a telerobotic sys-
tem, a viewing system, and a task support structure.
The telerobotic system consisted of a Kraft force-
reflecting master-slave manipulator. The viewing
system consisted of three camera views displayed on
two 21-inch monitors and one 9-inch monitor. The
21-inch monitors displayed close-up views of the
couplings from both front and rear, while the 9-
inch monitor displayed an overall view showing the
subject the orientation of the manipulator to the task
piece. The task support structure consisted of a 72-
inch by 48-inch metal frame upon which each coup-
ling was attached one at a time during testing. As
demonstrated in Figure 1, the designs of the four
couplings included in this study differed, as did
their actuation.
Coupling A was demated by grasping the outer
sleeve between the two flanges and applying axial
force toward the flex hose. It was demated when
enough force was applied to overcome the breakout
force of the coupling. Mating occurred by aligning
the coupling onto the nipple end and applying axial
force until the outer sleeve locked back into place.
This was the customized coupling designed specifi-
cally by Symetrics to be telerobotically and EVA
compatible. The flanges of the outer spool-shaped
sleeve were designed to be slightly wider than the
telerobotic grippers. This allowed some compli-
ance in grappling the fixture while still providing a
sufficient brace in order to apply the axial force
necessary for demating and mating. Another aspect
of coupling A's design which did not exist on the
other couplings was a chamfering of the entrance at
a 45 degree angle in order to guide the nipple por-
tion into the coupling. It was felt that these compli-
ant features would also lead to enhanced manual
operation of the coupling as well.
Coupling B had a very similar mechanism as coup-
ling A. The narrow outer ring was pulled toward
the flex hose until the breakout force of the coupling
was overcome and the coupling was demated.
Mating also occurred by aligning the coupling onto
the nipple end and applying axial force until the
coupling portion locked back into place.
Demating coupling C required depression of two
detents, one on either side of a knurled aluminum
ring. Once the detents were depressed, the alu-
minum ring would slide toward the flex hose and
the coupling portion could be pulled away. Mating
required aligning the coupling portion onto the
nipple end and applying force axially until the
detents engaged.
Coupling D had a lever-actuated demating process.
The coupling's lever was pushed toward the hard
mounted, nipple end. When the lever was pushed to
a certain point (approximately 45 degrees), demat-
ing automatically occurred. Mating required
aligning the coupling and applying axial force onto
the nipple end until the lever restored itself to the
vertical position.
It is important to note that the task performed in this
study does not represent the entire coupling process.
The experimental task consisted of, in effect, the
soft-latch phase of the coupling process where the
coupling is mated or demated but the actual flow of
fluid has not been affected. With each of these
couplings, the flow of fluid would need to be turned
on or off in an additional step not included in the
task. That phase of the coupling process would in-
volve the use of an added tool or a modification to
the end effector which would drive the coupling
into the fully opened or closed position. Since that
phase of the process has yet to be defined for Space
180
Mated
Hard mount -- Flex mount
Demated
I'l
Hard mount I_ Flex mount
A
Mated
Hard mount -- _ _- Flex mount
"t I_
Demated
Hard mount _ _ _ j! m_ Flex mount
C
Mated
Hard mount
Demated
Hard mount
B
Mated
Hard mount
Demated
Hard mount
D
Flex mount
i Flex mount
Flex mount
Flex mount
Figure 1. Schematic diagrams of the four couplings evaluated in this study.
Station Freedom operations, it was of interest to the
experimenters to evaluate the compatibility of the
mating and demating components of the task which
could be addressed at this time.
Design. This study implemented a 2 modality
(manual and telerobotic) by 4 coupling (couplings
A, B, C, and D) within subjects design. Modality
and coupling sequence was counterbalanced as
demonstrated in Table 1.
Procedure. To begin each testing session, subjects
were introduced to the purpose and procedure of
the study as well as the basic layout of the cameras,
task, and robotic system. Since subjects were
already familiar with the operation of the robotic
and viewing systems employed in the ROIL, no
instruction was necessary regarding these aspects of
the task.
Table 1. Counterbalancing sequence for coup-
lings and modality across subjects (M =
manual condition, T = telerobotic condi-
tion).
QD Coupling Sequence
1 2 3 4
Couo. A
MI T
Couv. B
TIM
Coup. C
M[ T
Coup. D
T I M
Coup. B
T] M
T
COUp. D
T ] M
Coup. A
MI T
Court. D
M[ T
M
Coup. B
MI T
Coup. C
TIM
_TOUF. CM
Coup. D
M| T
?uF 
T
Subjects began the session by manipulating a coup-
ling either manually or telerobotically depending on
their particular counterbalancing sequence. Each
coupling was demated and mated three times in each
modality. The experimenter kept performance time
by means of a hand stopwatch and recorded those
times on a data collection sheet where errors were
logged as well. An error was counted only if the
181
coupling portion was dropped. Timing would then
stop while the experimenter reset the coupling and
would restart as soon as the subject brought the arm
back into motion. Following a set of three trials
with each coupling, subjects filled out a short ques-
tionnaire with rating scales concerning workload,
discomfort, as well as various task related issues.
Once all the couplings had been completed, subjects
filled out a final questionnaire for each modality
where they rated the couplings in comparison to one
another.
RESULTS AND DISCUSSION
Analysis of Variance performed on the data showed
trends in both the performance as well as subjective
data. Table 2 presents the group means for many of
the performance and subjective measures. Due to
the very few number of errors occurring in any of
the trials, analysis of the error data resulted in no
significant findings and is not discussed.
It was hypothesized that as a result of the compliant
structures built into coupling A, demating and mat-
ing it would be faster than other couplings without
these structures built into them. Data from the
telerobotic trials showed that differences between
performance time across the couplings was signifi-
cant (F (3,3) = 4.372, p <.05). A Duncan's pairwise
comparison performed on the data showed that the
source of significance came largely from coupling
C being significantly slower than all other coup-
lings' performance time. Due primarily to the
small variance in the manual condition, differences
in performance time did not reach significance for
these trials. A Duncan's pairwise comparison on
these data, however, did show that performance
time for coupling A was significantly faster than
coupling C. As anticipated, it appears that for both
modalities, coupling A was faster - in some cases
significantly faster - to demate and mate than the
other couplings.
It was also felt that subjective reactions to the
couplings would show preference for the custom
coupling in both modalities. The overall rating data
were collected on seven point scales with 1 corre-
sponding to "completely acceptable" and 7 corre-
sponding to "completely unacceptable." As shown in
Table 2, these data revealed reliable differences,
this time for both telerobotic as well as manual
ratings. The data regarding the telerobotic prefer-
ence revealed an F (3,3) = 7.981 with a p <.01.
Pairwise comparisons showed that couplings A and
B were rated significantly more acceptable than
coupling C, while coupling A was significantly
more acceptable than coupling D. For the manual
ratings the data showed that F (3,3) = 8.007, with p
<.01. In this case pairwise comparisons indicated
that coupling C was significantly less acceptable
than all others. The comparable ratings attributed to
couplings A and B appeared the result of their simi-
lar mechanisms and operation. The shape of the
outer sleeve and coupling A's chamfering was all
that varied between the two.
Table 2. Group means for performance and sub-
jective measures.
Measure
Perform. Time
oer Trial (sec.'
Overall Rating
(1 to 7_
Grip Accep-
tability (1 to 7'
Mental Work-
load (1 to 10)
Phys. Discom
fort (1 to 7)
Modality of Operation
Telerobo_i¢
A B C D
66 77 450 168
1.5 2.0 5.3 3.8
1.3 2.8 3.5 2.8
3.0 2.5 6.8 4.0
2.5 1.5 3.8 2.5
Manual
A B C D
2.4 3.7 6.4 3.8
1.8 2.5 5.0 2.5
1.3 1.8 3.8 1.3
Not
Addressed
Using the same seven point scale described above,
data regarding the acceptability of obtaining the
proper grip did not reach significance for the tele-
robotic condition, although the pairwise compar-
isons did show that coupling A was rated signifi-
cantly more acceptable than coupling C. For the
manual condition this difference did reach signifi-
cance, F (3,3) = 5.368, p < .05, with the compar-
isons among the means indicating that coupling C
was significantly less acceptable than all three other
couplings.
After the telerobotic trials, data were also collected
on mental workload and physical discomfort. Data
from a Modified Cooper-Harper mental workload
rating scale reached significance, F (3,3) = 3.860,
p < .05. The pairwise comparisons showed that
couplings A and B were rated significantly less
mentally taxing than coupling C. Data from either
question addressing physical discomfort did not
reach significance although the pairwise compar-
isons tended to show couplings A and B as less
demanding than coupling C. These effects seemed
the result of the rather straight-forward mechanism
implemented on couplings A and B. Subjects only
had to grab and pull to demate couplings A and B,
while coupling C required depression of detents on
either side of the detention sleeve. This orientation
182
was often very difficult to achieve with the robotic
grippers, typically requiring repeated attempts
before demate finally occurred. Issues of mental
workload and physical discomfort were not ad-
dressed after the manual trials due to their very
short duration.
CONCLUSION
Of the couplings included in this study, the different
operational components resulted in varying reac-
tions from the subjects.
Regarding the demate process, subjects felt coupling
D included an attractive feature by requiring little
force to demate, achieving it simply by forcing the
lever over. However, maintaining control of the
coupling portion after demate proved difficult for
teleoperation, although somewhat easier for manual
operation. Demating coupling C showed that
depression of detents is a very delicate operation to
perform with the telerobot and to some extent, to
perform manually as well. Without some method of
fixing the orientation of the detents, it is very diffi-
cult to engage both at the same time, particularly
with the telerobot. This was compounded by the
fact that the depression had to be combined with the
axial force necessary to demate. Because of coup-
ling B's small outer ring, demating was at times
found to be clumsy with it as well. This was
particularly the case for the telerobotic condition,
but at times the manual condition was awkward as
well.
Mating the couplings proved, on the whole, a far
simpler process. Couplings B and D required close
alignment which, when met, resulted in a very
straight-forward mating process. Coupling C
incorporated a longer nipple portion to the coup-
ling. This assisted operation in both modalities by
helping to guide the coupling into the mated position
when the axial force was applied.
While coupling A did appear the better design in
this evaluation, there clearly were facets which
could be improved. Although the large flanges on
the outer sleeve assisted in mating, they also might
allow the telerobot or EVA astronaut to accidentally
bump or deactivate the coupling prior to full actua-
tion. Also, the chamfering performed on the entry
of the coupling was perhaps angled too far. The 45
degree entrance guided the nipple portion into the
coupling, but allowed sufficient misalignment such
that the coupling often bound just prior to fully
mating. Symetrics has recognized these concerns
and has provided the ROIL with a coupling address-
ing these issues by making two changes in the de-
sign. New shorter flanges still allow necessary sup-
port for the axial forces required, but greatly
reduce the likelihood of accidental deactivation.
The entry to the coupling was also chamfered to
approximately 30 degrees rather than 45. This
assisted in guiding the nipple into the coupling but
reduced the potential for binding by lessening the
amount of misalignment possible.
The purpose of this study was not to conceive the
final coupling design. Rather, it was intended as a
step along an iterative process. The newly modified
coupling will be included in a series of further con-
trolled as well as subjective evaluations. This is part
of ongoing work in the ROIL designed to enhance
the overall interface by improving design at both
the teleoperator and telerobot ends of the system.
AC KNOWLEDGEMENTS
Support for this investigation was provided by the
National Aeronautics and Space Administration
through Contract NAS9-17900 to Lockheed
Engineering and Sciences Company.
The authors would like to acknowledge John Calvin
and Steve Calvin of Symetrics Incorporated as well
as Ray Anderson of MacDonnell Douglas Space
Systems Company for their assistance in providing
materials and information crucial to this evaluation.
REFERENCES
Hannaford, B., Wood, L., Guggisberg, B.,
McAffee, D., and Zak, H. (1989). Performance
evaluation of a six-axis generalized force-reflecting
operator. (JPL Publication 89-18). Pasadena,
Califomia: NASA Jet Propulsion Laboratory.
National Aeronautics and Space Administration
(1989). Interface design considerations for robotic
satellite servicers. (NASA Report JSC-23920).
Satellite Servicing Systems Project Office.
Newport, C. (1989, June). Application of subsea
robotics maintenance experience to satellite servic-
ing. Paper presented at the Satellite Services
Workshop IV, NASA Johnson Space Center,
Houston, Texas.
183


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