The development test flight of the flight telerobotic servicer

8 Pages·3.9 MB·English

by  Andary, J.

THE DEVELOPMENT TEST FLIGHT
of the
FLIGHT TELEROBOTIC SERVICER
J. Andary and P. Spidaliere
Goddard Space Flight Center
Greenbelt, MD 20771
R. Sosnay
Martin Marietta Astronautics Group
Denver, CO 80201
ABSTRACT ics. The payload bpy element primary sup-
port structure is a Multi-Purpose Experi-
The Development Test Flight (DTF-1) is the ment Support Structure (MPESS) which me-
first of two shuttle flights to test oper- chanically attaches the DTF-1 hardware to
ations of the Flight Telerobotic Service?- the shuttle.
(FTS) in space and to demonstrate its ca-
pabilities in performing tasks for Space
Station Freedom. The DTF-1 system, which
Martin Marietta Astronautics Group is de-
signing and building for the Goddard Space
Flight Center, will be flown in December,
1991, as an attached payload on the shut-
tle. This article discusses the design of
the DTF-1 system, the tests to be per-
formed, and the data to be gathered.
INTRODUCTION
The FTS project was formed in 1986 as part
of the space station work package 3 at
Goddard Space Flight Center to develop a
telerobotic device for performing assem-
bly, maintenance, servicing and inspection
tasks on the space station [1,2]. Before
the final version is launched on one of Figure 1. Configuration of
the early space station assembly flights, Payload Bay Element for the
there will be two early shuttle test Development Test Flight
flights: the Development Test Flight
(DTF-1), now scheduled for launch in late The aft flight deck element consists of
1991, and the Demonstration Test Flight the control panels, the hand controller,
(DTF-2), scheduled for launch in late and the crew restraint system, which are
1993. The preliminary design review for removable and stowable in the mid deck
DTF-1 was held July, 1989, and the criti- locker. In addition there are permanently
cal design review is scheduled for Septem- mounted electronic boxes in the L-10 and
ber, 1990. L-11 panels.
From the initial beginnings of the FTS MISSION OVERVIEW
project, it was recognized that an early
development flight would be necessary in MISSION OBJECTIVES
order to validate the FTS hardware design
and to gather critical engineering test The DTF-1 flight hardware, flight soft-
data for ground evaluation and calibration ware, task elements and mission timeline
Of the ground testing facilities. The have been designed to meet the following
DTF-1 was designed under the ground rule mission objectives:
that the standard shuttle allocations for
a quarter-bay payload be used where possi- 1. Evaluate the telerobot manipulator
ble in order to contain costs and to main- design approach
tain schedule. 2. Evaluate the shuttle workstation
design approach
The DTF-1 configuration consists of a pay- 3. Correlate system performance in
load bay element and an aft flight deck space with ground
element. The payload bay element [figure simulation and analyses
11 contains the telerobot with a single 4. Evaluate human-machine interface
manipulator and all associated equipment, and operator fatigue
such as end-of-arm tooling, cameras and 5. Demonstrate telerobot potential
lights, task elements, and support avion- capabilities
151
A sequence of tasks will be performed dur- torque of 118 ft.lbs. The elbow pitch ac-
ing the 16-hour mission timeline to sup- tuator is capable of 61 ft.lbs. peak
port these objectives. After an initial torque. The wrist yaw, pitch and roll
system familiarization demonstration, the actuators are of similar design and each
remainder of the mission activities are produce a peak torque of 24 ft.lbs.
grouped into two main categories: perfor-
mance verification tasks and capabilities Figure 3 shows the Martin Marietta engi-
demonstration tasks. neering development wrist pitch/yaw
joints. The joint actuators consist of a
The performance verification tasks include primary brushless dc motor: harmonic drive
a fine positioning test, operational enve- transmission: redundant output joint
lope evaluation, manipulator dynamics torque sensors: redundant, resolver-based
model verification, manipulator non-linear output position sensors: fail-safe brakes:
model verification, and a thermal tran- and housings and bearings that carry
sient response test. The capabilities structural loads. The actuators also in-
demonstration tasks include the peg-in- corporate a secondary brushless motor,
hole demonstration, contour board track- which permits independent control and
ing, connector demate and mate, truss safing of the manipulator through a hard-
strut element removal and replacement, and wire control system, which bypasses all
removable mass manipulator loading test. the computers and allows the operator to
These tasks will be described in the.oper- drive a single joint at a time from the
ations section of this paper. workstation.
PAYLOAD BAY EQUIPMENT
The telerobot configuration used for DTF-1
consists of a single manipulator and a
modified telerobot body which is large
enough to support the manipulator and
mount the applicable subsystems. The
telerobot sits on the MPESS pallet in the
cargo bay facing the task panel. The ma-
nipulator is secured for launch and land-
ing by four caging mechanisms, two on the
lower arm link and two on the wrist. A
similar caging mechanism secures the re-
movable mass on the task panel.
The caging mechanism system is one-fault
tolerant against the inadvertent release
of the manipulator or removable mass under
all loading conditions. The caging mecha-
nism system is also one-fault tolerant to
safe the telerobot for landing.
Figure 3. Martin Marietta Engineering De-
Manipulator velopment Model of the Wrist Pitch/Yaw
Manipulator Joints
The DTF-1 manipulator [figure 21 is a 7-
The actuator brakes can be manually or
degree-of-freedom (DOF) manipulator, ap-
robotically engaged and disengaged to al-
proximately 5.5 feet long from the
low backdriving of joints. This back-
shoulder to the toolplate. The manipulator
can produce 20 pounds of force and 20 driving permits an astronaut on extra-
foot-pounds of torque at the tool plate vehicular activity (EVA) or, for future
missions, another robot, to stow the ma-
anywhere in the work envelope. The shoul-
nipulator in the event that the normal
der roll, yaw and pitch actuators are of
stowing procedure is disabled by a fail-
similar design and each produce a peak
ure. All the manipulator electronics are
contained within the manipulator.
i
'i
The manipulator, under active control,
will be accurate to only +/- 1 inch trans-
lation and +/- 3 degrees orientation. The
repeatability of the DTF-1 manipulator in
a thermally constant environment will be
less than +/- 0.005 inches translation and
+/- 0.05 degrees orientation. The incre-
mental motion or resolution of the manipu-
lators is less than 0.001 inches transla-
tion and less than 0.01 degrees orienta-
tion. All measurements are referenced at
Figure 2. FTS Manipulator the center of the tool plate.
152
The manipulator includes the camera assem-
SYMETRICS CONNECTOR
bly mounted on the wrist roll assembly to
allow the operator to closely view the end
effector and tool and the objects to be
manipulated. The camera will be discussed
further in the vision subsystem section.
TRUSS SEGMENT
A redundant force/torque transducer (FTT)
is mounted on the end of the manipulator.
The FTT contains two independent strain
gauge elements and associated electronics
for measuring the forces and torques pro-
duced at the tool plate. The output of
the FTT consists of two sets of six dif-
RIFA_OVABU£ MASS
ferential, analog signals which roughly
L_J
correspond to the six independent compo-
nents of the force and torque vectors.
The analog outputs are provided to two
independent controller electronics which
Figure 4. Task Panel
digitize and calibrate the signals to gen-
erate a digital representation of the is a prototype of the Space Station Free-
force and torque vectors at the FTT. dom data processor. It contains two 20
MHz CPUs with 4 MBytes memory. The tele-
The manipulator tool plate allows power, robot control computer is the primary con-
data and video to be passed through to the trol processor. In the forward loop, it
end effector. The DTF-I will fly a single takes commands from the hand controller,
end effector with a simulated end effector computes the inverse kinematics, and pro-
changeout mechanism (EECM). The EECM will duces the required motion at the manipula-
be used in future missions to permit re- tor. In the return loop, the control com-
placement of end effectors and tools. The puter receives inputs from the FTT, com-
DIF-I end effector will be a single paral- putes force feedback commands for the hand
lel jaw gripper which will perform all the controller, and performs boundary manage-
mission tasks. The end effector consists ment/touch control and housekeeping safety
of a brushless dc motor; pancake harmonic checks.
drive transmission; redundant finger posi-
tion and output torque sensors; redundant, The eight controllers include the display
fail-safe brakes and associated gear re- assembly controller and hand controller
duction; sensor amplifiers; wiring; and drive electronics located in the worksta-
connectors. The fingers are integral to tion, three controllers located in the
the end effector and interface to the manipulator, the telerobot redundant con-
tasks using a dedicated interface. The troller located on the MPESS, the power
end effector provides a peak gripping module controller, and the payload bay
force of 50 ibs. over a 4-inch gripping controller. The display assembly control-
range. ler and the hand controller drive elec-
tronics provide the operator interface
Task Panel
through the control and display panel and
hand controller respectively. The manipu-
The DTF-I task panel [figure 4] is mounted lator controllers perform the position,
on the MPESS in front of the manipulator. rate, and torque servo loop calculations
The task panel holds the task elements and drive the joint actuators and gripper.
which are designed to test the FTS's capa- The telerobot redundant controller col-
bility to meet the mission requirements. lects accelerometer data and performs
They consist of a peg-in- hole pattern, a backup boundary management/touch control
contour board, a space station truss node, checks and housekeeping checks. The power
a space station fluid connector, and a module controller monitors power subsystem
removable mass. voltages and currents and controls power
switching. The payload bay controller
Data Management and Processing Subsystem provides uplink and downlink through the
(DMPS) shuttle and controls the head cameras and
caging mechanisms. A typical controller
The DMPS is a distributed system of com- conslsts of a CPU board with an 80386, 20
puters, controllers, data and video re- MHz processor and 256 MBytes memory, a 22
corders, and hardwire control system that channel analog acquisition board, an in-
supports the DTF-I software and system put/output board, and a power supply
architectures. These electronics are con- board.
nected through MIL-STD-1553b
buses for data transfer.
The data recorders are used to initialize
the software and store on-orbit engineer-
The DTF-I configuration consists of one ing data. Initialization takes place
telerobot control computer and eight con- through the MIL-STD-1553b buses. Software
trollers. The telerobot control computer load files are pre-recorded before launch.
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Software files may be uploaded or down- The vision subsystem will be used in con-
loaded while on orbit through the shuttle junction with the shuttle's closed circuit
multiplexer/demultiplexer and payload data TV system. The camera video output will
interleaver respectively. interface to the shuttle's video switch
and be displayed on the existing shuttle
The software architectural design defines monitors. The output will also be record-
an organization of software components ed on the workstation video recorders.
corresponding to the NASA/National Bureau The wrist camera gives the operator a view
of Standards (NBS) Standard Reference Mod- of the end effectors, permitting intricate
el for Telerobot Control System architec- tasks to be performed and allowing close-
ture (NASREM), which is the FTS system
up inspections of completed work. The
functional architecture [3]. It also de-
head cameras each provide fixed views of
fines software components to support com- the worksite.
munications between NASREM modules, task
scheduling, and initial program load.
This design consists of a set of top-level AFT FLIGHT DECK ELEMENT
computer software components that corre-
spond to processor and read-only memory
device load modules and one set of lower The operator controls the telerobot and
conducts the DTF-I operations from the aft
level computer software components, most
flight deck of the shuttle. The work-
of which correspond to NASREM modules.
station is situated in the port-side cor-
ner of the aft flight deck close to the
The detailed software design is expressed
shuttle remote manipulator system (RMS)
in the Ada Program Design Language (PDL),
controls and uses the shuttle-provided TV
which is the adopted machine-compatible,
monitors that are located in that corner.
higher order language for space station.
The PDL permits the design to be expressed
in such a way that a compiler can be used The system is designed to be controlled by
to check the consistency of interfaces. a single operator, although an observer
All Ada specification sections are provid- may be used during the operation. Direct
ed in the detailed design, and components viewing of the telerobot will not be re-
(e.g. functions, procedures) in the body quired; however the operator will be able
sections are filled in to the extent that to see it through the aft flight deck win-
the compiler can perform its function. dows.
The remainder of the body may be filled in
with Ada expressions or descriptions of Workstation Subsystem
the processing logic of the components.
The workstation [figure 5] provides the
Power Subsystem
man-machine interface in the shuttle aft
flight deck for DTF-I operations. It uses
The power subsystem interfaces electrical- common hardware with the Space Station
ly with the shuttle's power system, condi- Freedom workstation and shuttle services
tions this power to meet the needs of the hardware. The DTF-I camera views will be
telerobot and distributes the power to the displayed on the existing Shuttle dis-
DTF-1 subsystem loads. The power subsystem plays. The shuttle-provided payload and
also performs the power switching required
by subsystem loads; performs line filter-
ing and EMI power quality filtering; pro-
vides power health status reports to the
computers; and permits a safe power-up and
power-down sequence.
The power subsystem generates three vol-
tages from the 28 VDC the shuttle pro-
vides. These are 120 VDC for the motors
and brakes, unregulated 28 VDC for the
DMPS and thermal control subsystems, and
regulated 28 VDC for the cameras and
lights. Future missions will use a regu-
lated and unregulated 120 VDC system.
Vision Subsystem
The vision subsystem includes one manip-
ulator wrist-mounted camera, two head-
mounted cameras, and camera lights. The
cameras are color and use charge coupled
device (CCD) technology. They and the Figure 5. General Layout of the Aft
lights are controlled from the worksta- Flight Deck for the
tion. Development Test Flight
154
general support computer(PGSCw) ill be
has been used in nuclear and undersea ap-
usedto display systemstatus andfunc-
plications since 1980.
tion. Theworkstation operator usesthe
functions keys andthe numericandcursor
The hand controller supports rate and po-
keypadfunctions of the PGSCkeyboardfor
sition control with and without force re-
menuanddata entry operation. A separate
flection. It can provide 5 pounds of
control anddisplay panel (C&DPh)as a
force and 9.5 inch-pounds of torque into
section of switches, indicators, andan-
the operator's hand. The hand controller
nunciators for manualcontrol, emergency
shutdown,andmodecontrol. ThePGSCand electronics consist of a computer, analog
to digital converter, input/output device,
C&DPare mountedto a commopnlate, which
and pulse-width modulated power drivers.
is mountedto the A8panel. Theworkstat-
ion configuration also incorporates a pow-
Each hand controller joint consists of an
er control anddistribution unit (PCDU),
induction motor and gearing, motor heat
display assemblycontroller, a crewre-
sink, potentiometer-based position sensor,
straint system,a 6-DOFhandcontroller,
and housings and bearings. The shoulder
andhandcontroller electronics.
and elbow joints contain additional speed
reduction. High gear ratios (200:1 in
Communication among the DTF-I subsystem the wrist joints) are used in conjunction
electronics elements is over a with low inertia motors and gears.
MIL-STD-1553b bus. This bus carries data
from the workstation to the telerobot sub- The detachable hand grip is similar to
systems. Such data includes joint posi- bottom-mounted, flight joysticks. It has
tions from the hand controllers and mode an activation switch, which activates the
commands from the control and display pan- hand controller and permits reindexing of
el. In the opposite direction, after be- the hand controller-to-manipulator trans-
ing transformed by the telerobot control formation; an end effector enable switch,
computer, manipulator force/ torque data which enables the end effector to open or
is transmitted over the bus for feedback close; and the end effector rocker switch,
to the operator through the hand control- which commands the end effector fingers to
ler. Health and status and alert informa- open or close.
tion is also transmitted over the bus for
data storage, analysis, and display to the Crew Restraint System
operator on the PGSC.
The crew restraint system consists of
Within the workstation subsystem, the PCDU pairs of adjustable padded bars which act
controls and monitors power distribution to restrain the operator from the hips
to the workstation electrical hardware. down. It provides restraint in all axes,
Video from the DTF-I head and wrist camer- permitting safe force reflecting opera-
as will be routed through the shuttle's tions in zero gravity.
video switch to the two shuttle monitors.
These same signals will be recorded on the The restraint system is designed to accom-
two shuttle video recorders located in the modate operators sized from a 95 percen-
LI0 panel. The operator will use the PGSC tile American male to a 5 percentile Japa-
keyboard through the display assembly or nese female. The system also has a thigh
the control and display panel controller crossbar vertical section that can rotate
to control the cameras. to place the pads against the front or
rear of the thighs. The entire system can
Hand Controller be rotated and tilted on the adapter so
the operator can be placed at the center-
The DTF-I hand controller is the Martin line of the monitors and 28 inches away
Marietta/Kraft 6-DOF, force-reflecting, from the monitors. In this location,
hand controller [figure 6]. The hand con- he/she can easily reach the C&DP and the
troller is based on a mature design that PGSC and maneuver the hand controller
throughout its operating envelope.
Hardwire Control
The C&DP has switches for bypassing the
computers and directly controlling the
telerobot, cameras and lights, individual
manipulator joints, manipulator and mass
caging mechanisms, and the end effector.
This hardwire control system permits stow-
age of the payload in the event of certain
failures of the DTF-I.
A safety emergency shutdown (ESD) switch
on the C&DP allows the operator to safely
Figure 6. Hand Controller shut down the telerobot. In the shuttle,
155
this switch will be hardwired to the robot Operational Envelope Evaluation
power distribution hardware. Activation of
this switch will cut all power to the ma- This automated sequence will evaluate the
nipulator motors and brakes. The other performance of the manipulator at work-
subsystems will not be affected. space extremes, test enroute velocity and
workspace limits, and demonstrate recovery
OPERATIONS when limits are exceeded.
DTF-I mission objectives will be met Manipulator Dynamics Model Verification
through a sequence of 12 tasks to be per-
formed during the 16-hour mission time- This task has two purposes: Test a joint
line. The first is an initial system closed loop actuator and structural dynam-
familiarization demonstration. The re- ics model and verify on-orbit stability
mainder of the mission activities are margins and the performance of the
grouped into six performance verification position-based impedance control.
tasks and five capabilities demonstration
tasks. For the joint closed loop actuator and
structural dynamics model test, automated
SYSTEM FAMILIARIZATION DEMONSTRATION sequence inputs will be given to the segen
joints, one at a time. The test will be
This task will demonstrate that the DTF-I performed for three different arm configu-
system and the operator are ready for per- rations, with the arm unloaded and then
forming the on-orbit DTF-I tasks. First, loaded with the gripper holding the
the manipulator and end effector will be 25-pound mass. The mass will be grasped
positioned well away from any surfaces or to verify the performance with different
objects that could be inadvertently con- inertias.
tacted. Then the following tests will be
conducted: For the automated impedance test, the ma-
nipulator will be rigidly connected to the
i) Test the boundary management/touch center handle of the caged mass and then a
control system. The purpose will be to step force or position command will be
verify that motion outside the workspace given in all 6-DOF.
will not occur. The operator will delib-
erately attempt to move the manipulator For the teleoperated tests, the operator
outside of the artificially established will use the handcontroller and different
boundaries defined in the software speci- force reflection gains to command gross
fically for this test. motions of the loaded manipulator. Dif-
ferent spring return forces will be used
2) Test the control available for single to test the resolved rate mode and deter-
joints. This test will confirm if the mine its operation.
operator can control the performance of
single joints from the control panel. Manipulator Non-linear Model Verification
Other tests will be to control and adjust This task provides the data to character-
the camera; operate the manipulator first ize and verify the non-linear model of the
with the handcontroller and then with the joints. Automated signal input sequences
hardwire system; control the manipulator will be input, one at a time, to shoulder
using various combinations of control pitch, elbow pitch, and wrist pitch.
mode, reference frames, and scale factors; Joint brakes except for the joint being
control the gripper with the C&DP and simulated will be ON. This task will be
hardwire system; and reindex the hand con- performed for three thermal conditions and
troller. in conjunction with the thermal transient
response tests.
PERFORMANCE VERIFICATION TASKS
Thermal Transient Response
Fine Positioning Test
This task will test the thermal capaci-
This test is an automated sequence that tance of the thermal control subsystem
will test the performance of the manipu- while evaluating manipulator performance
lator to ensure that accuracy, incremental under different thermal environments.
control, and repeatability performance re-
quirements are met. The accuracy test CAPABILITIES DEMONSTRATION TASKS
will be performed using the wrist camera
and an inverse prospective technfque. The Peg-in-Hole Demonstration
repeatability and incremental motion tests
will be performed using joint position An operator will use teleoperator control
sensors and forward transformation to the to insert a peg mounted on one of the fin-
tool plate. The ISO definitions, equa- gers into four different-sized holes. A
tions, and approaches will be used to de- video of the insertion and a transcript of
termine the results. the operator's comments will provide data,
156
including preciseness of peg insertion, uation of the manipulator performance in
depth of insertion, difficulties complet- both a loaded and unloaded configuration.
ing the task, and human-machine interface Two separate handles are provided on the
data, such as control preferences and hand mass for gripper attachment. The handle
controller feel, predicted stability, op- designs will incorporate mating interfaces
erator fatigue, and teleoperational mode matching the dedicated handle grasping
performance margins. interface of the end effector. One handle
is located on the center of gravity of the
Contour Board Tracking mass and the other is located off the cen-
ter of gravity in order to evaluate dif-
This task will evaluate impedance control ferent inertial loadings of the manipula-
and force reflection during end-point tor. The removable mass is the only
tracking tasks and provide engineering removable part of the task elements. A
data for evaluating the human-machine in- caging mechanism, similar in design to the
terface. An operator will use teleoper- lower arm caging mechanism, is provided
ation to control a peg in tracking curved, for the restraint of the mass.
straight-line and V-shaped machined trac-
ing paths, 3-D trajectories over rough SAFETY
surfaces, sloping plane surfaces and con-
vex, or concave contour surfaces. The The design of the DTF-I system is driven
task will be performed with and without heavily by safety considerations. Mission
force reflection but with active impedance procedures focus on maintaining the integ-
control. Data collected will include the rity of the shuttle and protecting the
operator's comments during the task and a crew. The DTF-I design ensures surviv-
video of the peg tracing the surface. ability after being subjected to normal or
emergency landing loads and post-landing
Connector Demate/Mate delays.
The gripper will demate and mate a Symmet- The telerobot may be shut down in three
rics connector, which will require multi- modes: Normal shut down, manual emergency
ple revolutions of its collar for locking shut down, and automatic emergency shut
and unlocking. This task is representa- down. In normal shut down, the operator
tive of an FTS task to be performed on can command the telerobot to shut down
Space Station Freedom. The engineering after it has completed work or when a
data generated will be used to determine failure occurs that is not hazardous to
the operational performance of the imped- the crew. The shutdown command may include
ance controller, bilateral force reflec- stowage of task element hardware.
tion, and manipulator safety limits and to
evaluate the human-machine interface. The In manual emergency shut down, the oper-
gripper will unlock and separate the con- ator may command shut down of the telero-
nector halves. Then the gripper will mate bot from the DTF-I workstation at which
the connector halves, lock them, and apply DTF-I operations are being monitored and
a small lateral force to verify the integ- controlled. This mode will be used to
rity of the connection. Throughout the respond to DTF-I failures that might be
repetitions of this task, the force re- hazardous to the crew, the shuttle struc-
flection gain will be varied as a function ture, or the telerobot.
of different gains. Task completion times
and contact force levels will be used to Automatic emergency shut down will allow
measure operator fatigue. the telerobot to shut itself down in the
event of a self-diagnosed failure or other
Truss Strut Element Removal/Replacement unsafe condition. Such conditions include
the failure of the shuttle or support sys-
This task is another FTS-like task in tem to supply required power and/or data
which a Space Station Freedom truss strut links and the possibility of the telerobot
element will be removed and replaced. The colliding with itself or other structures.
gripper will grasp the collar on the truss The telerobot will shut itself down auto-
strut element mounted on the task panel matically when these failures occur or
and unlock and relock it. The strut will when an out-of-limits condition exists.
then be partially demated from the strut After corrective actions or workarounds
attachment fitting mounted on the node. have been implemented, the operator can go
Engineering performance data on the imped- through the normal startup and checkout
ance controller, force reflection, and procedures to continue working. If the
manipulator safety limits will be generat- arm becomes partially inoperable, degraded
ed. Human-machine interface and operator mission operations could continue. The
fatigue will be evaluated from operator safety of the crew and the shuttle will be
comments and a video of the task. comsidered to be paramount. Those tasks
that require full operability and that
Removable Mass Manipulator Loading Test were not completed when the arm failed
will be removed from remaining mission
A 25-pound removable mass that is caged to profile timeline. The hardwire control
the task panel is provided to enable eval- scheme will be implemented to restore the
157
manipulator in the event a failure pre- deck of the shuttle. This data will be
cludes computer control of the arm. analyzed post flight, and the results will
be used in the development of the final
In the unlikely event that a failure or flight system which will be used in the
series of failures prevents the manipula- assembly and maintenance of Space Station
tor or removable mass from being restowed Freedom.
by the normal method or by hardwire con-
trol, there is equipment that will allow
REFERENCES
the DTF-I payload to be jettisoned using
the shuttle RMS.
1. Andary, J.; S. Hinkal; and J.Watzin;
A third hazard control will be to use EVA "Design Concept for the Flight Tele-
to restow the payload for safe shuttle robotic Servicer (FTS)," presented at
reentry and landing. The manipulator and the 2nd Space Operations Automation
gripper are designed so that an astronaut and Robotics Workshop (SOAR88), Day-
on EVA can manually release the brakes on ton, OH, July 20-23, 1988; NASA Con-
them if they fail and backdrive the system ference Publication CP-3019, pp.
into the correct position for caging. If 391-396.
a manipulator joint seizes, thereby pre-
venting restow, the astronauts can remove 2. Andary, J.; K. Halterman; K. Hewitt;
the manipulator at the shoulder and stow and P. Sabelhaus; "The Flight Telero-
it on the failed manipulator arm storage botic Servicer (FTS) : NASA's First
system (FMASS) which is attached to the Operational Robotic System," presented
MPESS. at the 3rd Operations Automation and
Robotics Workshop (SOAR89), Houston,
CONCLUSION TX, July 25-27, 1989; NASA Conference
Publication CP-3059, pp. 311-318.
During the 16 hours of mission operation,
the Development Test Flight will return 3. Albus, J.; H. McCain; and R. Lumia;
valuable engineering data on the perfor- NASA/National Bureau of Standards
mance of the FTS manipulator in zero grav- (NBS) Standard Reference Model for
ity and on the human-machine interfaces Telerobot Control System Architecture
necessary for the efficient operation of a (NASREM), SS-GSFC-0027, December 4,
teleoperated system from the aft flight 1986.
158