Deployment and Retrieval System
The payload deployment and retrieval system includes the electromechanical
arm that maneuvers a payload from the payload bay of the space
shuttle orbiter to its deployment position and then releases it.
It can also grapple a free-flying payload, maneuver it to the
payload bay of the orbiter and berth it in the orbiter. This arm
is referred to as the remote manipulator system.
The RMS is installed in the payload bay of the orbiter for those
missions requiring it. Some payloads carried aboard the orbiter
for deployment do not require the RMS.
The RMS is capable of deploying or retrieving payloads weighing
up to 65,000 pounds. The RMS can also retrieve, repair and deploy
satellites; provide a mobile extension ladder for extravehicular
activity crew members for work stations or foot restraints; and
be used as an inspection aid to allow the flight crew members
to view the orbiter's or payload's surfaces through a television
camera on the RMS.
The PDRS was built via an international agreement between the
National Research Council of Canada and NASA. Spar Aerospace Ltd.,
a Canadian company, designed, developed, tested and built the
RMS. CAE Electronics Ltd. in Montreal provides electronic interfaces,
servoamplifiers and power conditioners. Dilworth, Secord, Meagher
and Assoc. Ltd. in Toronto is responsible for the RMS end effector.
Rockwell International's Space Transportation Systems Division
designed, developed, tested and built the systems used to attach
the RMS to the payload bay of the orbiter.
The basic RMS configuration consists of a manipulator arm; an
RMS display and control panel, including rotational and translational
hand controllers at the orbiter aft flight deck flight crew station;
and a manipulator controller interface unit that interfaces with
the orbiter computer. Normally, only one RMS is installed on the
left longeron of the orbiter payload bay. The RMS could be installed
on the right side, but the orbiter Ku-band antenna would have
to be removed to accommodate the RMS there. Two arms could be
installed in the payload bay if the orbiter Ku-band antenna were
removed, but only one arm could be operated at a time because
only a single software package (computer program) and a single
set of display and control panel hardware are provided at the
flight deck aft control station. Electrical wiring is in the flight
deck aft station for both arms.
One flight crew member operates the RMS from the aft flight deck
control station, and a second flight crew member usually assists
with television camera operations. This allows the RMS operator
to view RMS operations through the aft flight deck payload and
overhead windows and through the closed-circuit television monitors
at the aft flight deck station.
The RMS arm is 50 feet 3 inches long and 15 inches in diameter
and has six degrees of freedom. It weighs 905 pounds, and the
total system weighs 994 pounds.
The RMS has six joints that correspond roughly to the joints
of the human arm, with shoulder yaw and pitch joints; an elbow
pitch joint; and wrist pitch, yaw and roll joints. The end effector
is the unit at the end of the wrist that actually grabs, or grapples,
the payload. The two lightweight boom segments are called the
upper and lower arms. The upper boom connects the shoulder and
elbow joints, and the lower boom connects the elbow and wrist
joints. The RMS arm attaches to the orbiter payload bay longeron
at the shoulder manipulator positioning mechanism. Power and data
connections are located at the shoulder MPM.
The RMS can operate with standard or special-purpose end effectors.
The standard end effector can grapple a payload, keep it rigidly
attached as long as required and then release it. Special-purpose
end effectors are designed by payload developers and installed
instead of the standard end effector during ground turnaround.
An optional payload electrical connector can receive electrical
power through a connector located in the standard end effector.
The booms are made of graphite epoxy. They are 13 inches in diameter
by 17 feet and 20 feet, respectively, in length and are attached
by metallic joints. The composite in one arm weighs 93 pounds.
The joint and electronic housings are made of aluminum alloy.
A shoulder brace relieves launch loads on the shoulder pitch
gear train of the RMS. On orbit, the brace is released to allow
RMS operations. It cannot be relatched on orbit, but it is not
required that it be relatched for entry or landing loads. A plunger
is extended between two pieces of tapered metal, pushing the ends
of the pieces outward, wedging the ends of the receptacle on the
outer casing of the shoulder yaw joint, and engaging the shoulder
brace. Shoulder brace release is controlled by the lever-locked
shoulder brace release starboard, port switch on panel A8U. Normally,
the RMS arm is installed on the orbiter's port, or left, side.
Positioning the switch to port releases the port shoulder brace,
which withdraws the plunger by an electrical linear actuator.
This allows the tapered metal pieces to relax and move toward
each other, which permits the brace to slide out of the shoulder
yaw outer casing, unlatching the brace. The switch must be held
until the shoulder brace release talkback indicator on panel A8U
indicates gray, which usually takes six to nine seconds. A microswitch
at the end of the plunger's travel controls the talkback indicator.
A barberpole indication shows that the shoulder brace is still
latched. The shoulder brace release switch and talkback indicator
cannot receive electrical power until the RMS select switch and
RMS power switch on panel A8L are positioned for electrical power.
The RMS select switch on panel A8L selects the arm to be used,
or it indicates off if no arm is to be used. The switch essentially
tells the manipulator controller interface unit and display and
control panel A8L which arm is being powered and operated. The
status of the switch is also displayed on the aft flight control
station CRT display.
The RMS power switch on panel A8L has a guard over it and connects
orbiter main dc bus and AC1 phase A power to the RMS, MCIU and
displays and controls on panels A8L and A8U when positioned to
primary . Main dc bus and AC2 phase A power are connected to the
RMS and some displays and controls on panels A8L and A8U when
the switch is positioned to backup . The status of the switch
is also displayed on the aft flight deck CRT. The off position
removes all power from the selected arm. Panel A8L has a set of
switches for the starboard RMS on the left side and an identical
set for the port RMS on the right side of the panel that controls
the selected RMS heaters, retention system and positioning mechanism.
Normally, the port RMS set of switches is used.
The RMS is rotated 31.36 degrees toward the payload so the payload
bay doors can be closed and is rotated 31.36 degrees away from
the payload bay when the payload bay doors are opened. The manipulator
positioning mechanism rolls the arm from its stowed position (toward
the payload bay) to its operating position (away from the payload
bay). The MPM consists of four pedestal joints joined by a torque
tube and operated as a single assembly. The shoulder of the RMS
arm attaches to the orbiter payload bay longeron (the sill of
the bay) at the forwardmost MPM pedestal, and the aft three MPM
pedestals contain latches that secure the arm along the orbiter
payload bay longeron.
The RMS MPM assembly rotation is controlled by the guarded RMS
deploy, off, stow switch on panel A8L. When the switch is positioned
to deploy, two redundant ac motors drive the MPM assembly to the
deploy position; and two microswitches, one for each motor located
on the MPM shoulder, remove electrical power from that ac motor
when it reaches its limit of travel. With both ac motors operat
ing, it takes approximately 34 seconds to deploy the RMS. If only
one ac motor is operating, it takes approximately 68 seconds to
deploy the RMS. When the switch is positioned to stow, the ac
motors drive the MPM assembly to the stow position; and two other
microswitches, one for each motor located on the MPM shoulder,
remove electrical power from that ac motor when it reaches its
limit of travel. The operating time to the stow position for both
motors or one motor is the same as in the deploy mode. The status
of these four microswitches can be monitored by the flight crew
on the aft flight station CRT and by telemetry. The off position
removes electrical power from the MPM.
An RMS talkback indicator above the RMS deploy, off, stow switch
on panel A8L indicates sto when the arm is stowed, barberpole
when the arm is in transit and dep when the arm is deployed. The
talkback indicator is controlled by four microswitches on each
of the four pedestals. These microswitches can also be monitored
A manipulator retention latch is located in each of the three
aft MPM pedestals. It locks a corresponding striker bar on the
arm, locking the arm to the MPM.
When the RMS retention latches, release, off, latch switch on
panel A8L is positioned to release , each MRL has two redundant
ac motors that drive the MRL open; and two microswitches, one
for each motor on each MRL, remove electrical power from that
ac motor when it reaches its limit of travel. With both ac motors
operating, it takes approximately eight seconds to fully open
that latch. If only one ac motor is in operation, it takes approximately
18 seconds for the latch to fully open. The talkback indicator
above the release, off, latch switch on panel A8L indicates barberpole
when the MRLs are in transit and rel when they are released. There
are two release microswitches on each of the MRLs that control
the talkback indicator. These microswitches can be monitored by
the flight crew on the aft flight deck CRT.
The RMS arm is now available for operation.
When the RMS arm is properly aligned and resting on the MPM pedestals
for latching to the MPMs, the three RMS striker bars are in the
MRL ready-to-latch envelope. Two microswitches in each MRL control
the corresponding aft, mid, or fwd ready for latch talkback indicators
on panel A8L. When the talkback indicators show gray, the corresponding
MRL is positioned to latch the corresponding arm striker bar.
If a talkback indicator shows barberpole, the MRL is not correctly
aligned or not in position to be able to latch down the arm. As
a result, the flight crew must reposition the arm until the talkback
indicators show gray. These microswitches can be monitored by
the flight crew at the aft flight deck CRT. When the flight crew
sees three gray ready for latch talkbacks, it positions the retention
latches switch to latch. The two ac motors in each MRL drive the
MRL closed; and two microswitches, one for each motor, remove
electrical power from that ac motor when it reaches its limit
of travel. The operating time for both motors or one motor would
be the same as for release.
The talkback indicator above the release, off, latch switch indicates
barberpole when the MRLs are in transit and lat when they are
latched, thus holding the arm in the MRLs.
The RMS has both passive and active thermal control systems.
The passive system consists of multilayer insulation blankets
and thermal coatings that reflect solar energy away from the arm
and aid in controlling the temperature of the hardware. The blankets
are attached to the arm structure and to each other with Velcro.
Exposed areas around the moving parts are painted with a special
white paint. To maintain the arm's temperature within predetermined
operating limits, an active system, which consists of 26 heaters
on the arm, supplies 520 watts of power at 28 volts dc. There
are two redundant heater systems: one powered from the orbiter's
main A dc bus and the other from the main B dc bus. Only one system
is required for proper thermal control. The heaters in each system
are concentrated at the arm's joint and end effector to heat the
electronics and ac motor modules. The heaters are enabled by the
heater auto, off guarded switch on panel A8L. When the switch
is positioned to auto, the heaters are thermostatically controlled
by 12 thermistors located along the arm. The heaters are automatically
turned on at 14 F and off at 43 F.
The light-emitting diodes 1, 2 and 3 on panel A8U can be used
in conjunction with the joint and parameter rotary switches on
panel A8U to display arm temperatures in degrees Farenheit along
with identification numbers. When the joint rotary switch is positioned
to end eff temp and the parameter rotary switch is positioned
to port or stbd (normally port ), LED 1 displays the commutator's
temperature, LED 2 displays the end effector electronics' temperature,
and LED 3 identifies the end effector. The stbd temp or port temp
caution and warning light (normally port ) on panel A8U indicates
a joint has reached a critical temperature. When the joint rotary
switch is positioned to crit temp and the parameter rotary switch
is positioned to stbd or port, the LED 1 digital display shows
the commutator's temperature, the LED 2 digital display shows
the temperature of the housing arm-based electronics, and the
LED 3 digital display identifies the joint that has the most out-of-limit
temperature. Temperatures are also monitored by software.
The orbiter's CCTV aids the flight crew in monitoring PDRS operations.
The arm has provisions on the wrist joint for a CCTV camera that
can be zoomed, a viewing light on the wrist joint and a CCTV with
pan and tilt capability on the elbow of the arm. In addition,
four CCTV cameras in the payload bay can be panned, tilted and
zoomed. Keel cameras may be provided, depending on the mission
payload. The two CCTV monitors at the aft flight deck station
can each display any two of the CCTV camera views simultaneously
with split screen capability. This shows two views on the same
monitor, which allows crew members to work with four different
views at once. Crew members can also view payload operations through
the aft flight station overhead and aft (payload) viewing windows.
The RMS can only be operated in a zero-gravity environment, since
the arm dc motors are unable to move the arm's weight under the
influence of Earth's gravity. Each of the six joints has an extensive
range of motion, allowing the arm to reach across the payload
bay, over the crew compartment or to areas on the undersurface
of the orbiter. Arm joint travel limits are annunciated to the
flight crew arm operator before the actual mechanical hardstop
for a joint is reached.
Each joint of the arm is driven electromechanically. Each joint
has one dc motor and associated ABE. Each dc motor turns a gear
train, which produces joint motion. A tachometer on the output
side of each motor measures motor rate. Also, on the output side
of the gear train is an optical encoder that measures the actual
joint angle and feeds it back to the software. There are two optical
commutators on the input side of each motor: one commutator electronically
interfaces with the primary motor drive amplifier; and one electronically
interfaces with the backup drive amplifier, which is the only
redundancy in each joint motor.
The arm has a number of operating modes. Some of these modes
are computer-assisted, moving the joints simultaneously as required
to put the end point (the point of resolution, such as the tip
of the end effector) in the desired location. Other modes move
one joint at a time; e.g., single mode uses software assistance
and direct and backup hard-wired command paths that bypass the
When the arm is used in the computer-assisted mode, the command
from the flight crew operator is converted by the computer to
a set of motor speeds (one for each joint) that move the arm to
the desired configuration. The software scales down the set of
commands so that no joint exceeds the maximum allowable joint
rate. This is called rate limiting, with the maximum joint rates
dependent on the payload being flown and chosen so the arm can
be stopped in 2 feet. The software also checks that the POR can
be stopped within 2 feet. This is called POR rate limiting. For
example, the tip of the unloaded arm cannot be moved more than
2 feet per second, and a 32,000-pound payload cannot be moved
more than 0.2 foot per second.
The motor drive amplifier for each joint (total of six) can receive
either a hard-wired direct drive input when the arm is not in
the computer-assisted mode of operation or receive the error signal
from the tachometer feedback loop. When the MDA receives its signal
from the feedback loop, it gets additional input, called the current
limit command, from the computer. This input controls the maximum
torque of the motor; thus, arm loads are maintained within the
defined limits while operating. The current limit can only be
changed with a computer memory read/write procedure.
One backup drive amplifier for the entire arm is located in the
shoulder electronics compartment. When the arm is operated in
the backup mode, the drive unit goes to the motor via the BDA
and bypasses the feedback loop.
Normal braking is accomplished by each joint motor deceleration;
however, each joint has a mechanical friction-type brake, and
all six brakes are operated by a single switch on panel A8U. When
the brakes on, off switch is positioned to on, brakes in all joints
of the arm are applied. The brakes are applied only after all
joints are brought to rest or for an emergency and should be left
on whenever the arm is unattended. The switch positioned to off
removes the brakes from all joints of the arm. The talkback indicator
above the brakes switch on panel A8U indicates when the brakes
are on or off.
The standard end effector can be considered the hand of the RMS.
It is a hollow canlike device attached to the wrist roll joint
at the end of the arm. Payloads to be captured by the standard
end effector must be equipped with a grapple fixture. To capture
a payload, the flight crew operator aligns the end effector over
the grapple fixture probe to capture it. The end effector snare
consists of three cables that have one end attached to a fixed
ring and one attached to a rotating ring.
The end effector extend talkback indicator on panel A8U indicates
gray when the end effector snare assembly is fully extended toward
the opening of the canister. Barberpole indicates the end effector
snares are somewhere between rigidize and derigidize.
The end effector open talkback indicator on panel A8U indicates
gray when the snares are fully open. Barberpole indicates the
snares are not fully open.
An end effector capture/release rocker switch on the RMS rotational
hand controller at the aft flight deck station is positioned to
capture by depressing the bottom half of the rocker switch. The
switch commands capture of the payload by rotating the inner cage
assembly three-wire snares around the payload-mounted grapple
fixture probe and centers the payload grapple fixture in the end
effector. The RMS RHC end effector capture switch must be held
until the payload-mounted grapple fixture is centered. The RMS
RHC end effector capture switch is powered only if the end effector
mode switch is in auto or man .
The end effector capture talkback indicator on panel A8U indicates
gray when the snares have closed on the payload grapple fixture
probe. Barberpole indicates the end effector has not captured
the payload grapple fixture.
The end effector close talkback indicator on panel A8U indicates
gray when the snares have fully closed on the payload grapple
fixture probe and the probe is centered in the end effector. Barberpole
indicates that the snares are not fully closed. The end effector
derigid talkback indicator on panel A8U indicates gray when the
end effector snare assembly is fully extended.
The payload is rigidized by drawing the snare assembly inside
the end effector using a jackscrew, pulling the payload tightly
against the face of the end effector and rigidizing the arm/payload
assembly. During this process, current limit commands are sent
to each joint motor to limp the arm, allowing the arm to move
and compensate for misalignment errors. Wrist roll can still be
commanded with a limp arm. The end effector rigid talkback indicator
on panel A8U indicates gray when the end effector snare assembly
is fully withdrawn in the end effector canister and the payload
is rigidized. Barberpole indicates the end effector and payload
are not rigidized.
There is one dual-end motor that produces all the motion in the
end effector. The end effector electronics unit processes the
end effector commands to produce the appropriate motor, clutch
and brake commands from the displays and controls.
The rigidize sequence can be accomplished automatically or manually.
The mode is selected by the flight crew operator with the end
effector mode auto, off, man switch on panel A8U. Positioning
the switch to auto causes the rigidize sequence to proceed automatically.
If the switch is positioned to man , the end effector man contr
switch on panel A8U must be positioned to rigid .
To release a payload, the snare mechanism moves outward until
there is no force pulling the payload against the end effector,
which is called derigidizing. If the end effector mode auto, off,
man switch is in auto, lifting the RMS RHC switch guard and depressing
the top half of the rocker switch commands a release. Derigidization
automatically occurs, the snares of the end effector rotate open,
and the payload grapple fixture is released. If the switch is
positioned to man , the end effector man contr switch on panel
A8U must be positioned to derigid .
The end effector rigid talkback indicator indicates barberpole
when the end effector is no longer rigidized. The end effector
derigid talkback indicator indicates gray when the end effector
is derigidized. The end effector extend talkback indicator indicates
gray when the end effector is fully extended. The end effector
open talkback indicator indicates gray when the snares are fully
open, releasing the payload, and the end effector close talkback
indicator indicates barberpole.
The end effector is also equipped with a backup release capability
that is controlled by the lever-locked payload release, off switch
on panel A8U. The switch is only powered when the RMS power switch
on panel A8L is positioned to backup . When the snares are closed,
the snares wind up a spring device in the end effector. When the
RMS power switch is in backup and the payload release switch is
positioned to on, the snares are opened by the energy stored in
the spring, releasing the payload. The end effector does not derigidize
before releasing the payload. The payload release switch positioned
to off de-energizes the circuit that opened the snares.
There are two types of automatic modes that can be used to position
the RMS arm: preprogrammed and operator-commanded. The RMS software
may be placed in the auto mode by positioning the mode rotary
switch on panel A8U to auto 1, auto 2, auto 3, auto 4 or opr cmd
and depressing the enter push button indicator on panel A8U. RMS
joint rate commands are computed to drive the arm from its present
position to a given point. (Point refers to a position and attitude
of the point of resolution relative to the orbiter.) The RMS joint
rates are computed so that the desired position and attitude are
reached at the same time.
The operator-commanded automatic mode moves the end effector
from its present position and orientation to a new one defined
by the operator via the keyboard and RMS CRT display. After the
data are keyed in, the operator must do a command check to verify
that there is a set of joint angles that will put the arm at the
desired point, but this command check does not verify the trajectory
the arm must travel to get to that point (a straight line). If
the point is valid, good appears on the CRT; if not, fail appears.
The mode is then entered by selecting opr cmd on the rotary mode
switch, positioning the brakes switch to off , and depressing
the enter push button indicator. The white ready light on panel
A8U then is illuminated. To start the arm moving to the desired
point, the auto seq switch on panel A8U is positioned momentarily
to proceed. The ready light is extinguished, and the white in
prog light on panel A8U is illuminated. The arm will move in a
straight line to the desired position and orientation, the in
prog light will be extinguished, and the arm will then enter the
hold mode. The RMS operator can stop and start the sequence through
the auto seq proceed, stop switch on panel A8U.
The preprogrammed auto sequences operate in a manner similar
to the operator-commanded sequences. Instead of the RMS operator
entering the data on the computer via the keyboard and CRT display,
the RMS arm is maneuvered according to sets programmed before
the flight, called sequences. Up to 200 points may be preprogrammed
into as many as 20 sequences. A given sequence is assigned via
the CRT into auto 1, auto 2, auto 3 or auto 4. The mode is determined
by then selecting auto 1, auto 2, auto 3 or auto 4 on the rotary
mode switch and depressing the enter push button indicator. Each
sequence is an ordered set of points to which the arm will move.
The preprogrammed sequences also consist of pause and fly-by.
Pauses may be preprogrammed into the arm trajectory at any point
that will cause the arm to come to rest. In order for the arm
to proceed with the automatic sequence, the auto seq proceed,
stop switch is positioned to proceed . (The operator can stop
the arm at any place in the auto sequence by positioning the auto
seq switch to stop .) When the last point in the sequence is reached,
the computer will terminate the movement of the arm and enter
a position hold mode. The speed of the end effector between points
in a sequence is governed by the individual joint rate limits
set in the RMS software. In the fly-by sequence, the arm does
not stop at a fly-by point; it continues to the next point in
The single-joint drive control mode enables the operator to move
the arm on a joint-by-joint basis with full computer support,
thereby enabling full use of joint drive characteristics on a
joint-by-joint basis. The operator places the rotary mode switch
in the single position, depresses the enter push button indicator,
and operates the arm by driving one joint at a time with the joint
rotary switch on panel A8U and the single/direct drive switch
on panel A8U. In this mode, actuation of the single/direct drive
switch removes the brakes from the joint that is selected by the
joint rotary switch. The computer sends rate commands to the selected
joint while holding position on the other joints. The single-joint
drive mode is used to stow and unstow the arm and drive it out
of joint travel limits.
Direct-drive control is a contingency mode. The direct mode is
selected by positioning the rotary mode switch to direct and the
brakes switch to on; the individual joints are driven with the
rotary joint switch and the single/direct drive + or - switch.
In the direct mode, the brakes remain on those joints not being
driven, and the drive commands are hard-wired to the selected
joint. Direct drive bypasses the manipulator control interface
unit, computer and data buses to send a direct command to the
motor drive amplifier. The direct-drive mode is used when the
MCIU or computer has a problem that necessitates arm control by
the direct-drive mode to maneuver the loaded arm to a safe payload
release position or to maneuver the unloaded arm to the storage
position. Since this is a contingency mode, full joint performance
characteristics are not available. Computer-supported displays
may or may not be available, depending on the fault that necessitated
the use of direct drive.
Backup drive control is a contingency mode to be used when the
prime channel drive modes are not available. The backup is a degraded
joint-by-joint drive system. The RMS software is in a suspend
mode when backup is selected. The backup mode is selected by positioning
the RMS power switch on panel A8L to backup . The arm is controlled
using the backup control rotary switch on panel A8U and the single/direct
drive + or - switch located below the rotary switch. The brakes
are on the joints not being driven. The motors are driven bypassing
the servoloop system. Since the MCIU has no power, there are no
data from the arm.
Four RMS manually augmented modes are used to grapple a payload
and maneuver it into or out of the orbiter payload retention fittings.
The four manually augmented modes require the RMS operator to
use the RMS translational hand controller and rotational hand
controller with the computer to augment operations. The RMS takes
up 32 percent of the fifth central processor unit for RMS operation
and 30 percent for the manually augmented modes. The four manually
augmented modes are controlled by the mode rotary switch on panel
A8U. The modes are orbiter unloaded, end effector, orbiter loaded
or payload. The coordinate system to which the motion is referred
and point of resolution differ for each of these modes.
The THC and RHC located at the aft flight deck station are used
exclusively for RMS operations. The THC is located between the
two aft viewing windows. The RHC is located on the left side of
the aft flight station below the CCTV monitors. The THC and RHC
have only one output channel per axis. Both RMS hand controllers
are proportional, which means that the command supplied is linearly
proportional to the deflection of the controller.
The RHC has additional switches on it. A rate hold push button
on top of the RHC allows the RMS operator to maintain the RHC
and THC inputs that are applied when the push button is engaged.
Rate hold is disengaged when the push button is actuated again.
Next to the rate hold push button is a rate limit vernier/coarse
slide switch. In the forward position (away from the RMS operator),
the operator uses the coarse rates. In coarse, the maximum rate
of end effector movement for an unloaded arm is 2 feet per second,
0.2 foot per second for a loaded arm with a 32,000-pound payload,
and 0.1 foot per second for 65,000-pound payloads. Sliding the
switch toward the operator limits the maximum rate of end effector
movement to lower speeds (vernier). For example, unloaded arm
rates are limited to 0.61 foot per second and loaded arm rates
to 0.061 foot per second. In vernier, maximum rates are loaded
for a given payload.
The manually augmented mode enables the RMS operator to direct
the end effector of the arm using two three-degree-of-freedom
RMS hand controllers to control the end effector translation and
rotation rates. The control alogrithms process the hand controller
signals into a rate for each joint.
When a manually augmented mode is selected, rate commands from
the RMS THC result in motions at the tip of the end effector that
are parallel to the orbiter-referenced coordinate frame and compatible
with the up/down, left/right, in/out direction of the THC. Commands
from the RMS RHC result in rotation at the tip of the end effector,
which is also about the orbiter-referenced coordinate frame.
The manually augmented end effector mode maintains compatibility
at all times among rate commands at the THC and RHC and the instantaneous
orientation of the end effector. The end effector mode is used
for grappling operations in conjunction with the RMS wrist-mounted
CCTV camera, which is oriented with the end effector coordinates
and rolls with the end effector. The CCTV scene presented on the
television monitor has viewing axes that are oriented with the
end effector's coordinate frame. This results in compatible motion
among the rate commands applied at the hand controllers and movement
of the background image presented on the television monitor. Up/down,
left/right and in/out motions of the THC result in the same direction
of motion of the end effector as seen on the television monitor,
except that the background in the scene will move in the opposite
direction. Therefore, the operator must remember to use a fly-to
control strategy and apply commands to the THC and RHC that are
toward the target area in the television scene.
The manually augmented orbiter-loaded mode enables the operator
to translate and rotate a payload about the orbiter axis with
the point of resolution of the resolved rate algorithm at a predetermined
point within the payload, normally the center of geometry. This
allows for pure rotations of the payload for berthing operations.
The manually augmented payload mode is analogous to the manually
augmented end effector mode.
Each RMS joint has travel limits. The wrist pitch joint is an
example. This joint can be physically moved to plus or minus 121.4
degrees to the mechanical hardstop. At plus or minus 114.4 degrees,
the arm is at its reach limit, where the software warns the RMS
operator by activating the yellow reach limit light, the master
alarm push button indicator and tone on panel A8U, a computer
fault message, an SM tone and a reach limit indication on the
CRT. If the RMS operator continues driving the joint past the
reach limit, the next warning is the joint's softstop. At this
point (plus or minus 116.4 degrees for the wrist pitch joint),
the software stop talkback on panel A8U will indicate barberpole.
The arm will drop out of mode (if it was being driven in one of
the computer-augmented modes) and be unable to be driven further
without operator action. The arm can only be operated in the single,
direct or backup modes once it reaches a softstop. If one continues
to drive the joint in this direction, motion will stop at plus
or minus 121.4 degrees for wrist pitch because a joint cannot
be driven past its hardstop. All joint angles equal zero degrees
when the arm is cradled.
Safing and braking are the two methods available for bringing
the arm to rest. Safing can be accomplished by positioning the
safing switch on panel A8U to safe , which brings the arm to rest
using the servocontrol loops. When the safing switch is positioned
to auto , safing is initiated by the MCIU when certain critical
built-in test equipment failures are detected. The cancel position
of the safing switch removes the safing state. The safing talkback
indicator indicates gray when safing is not in progress and barberpole
when safing is in progress.
The RMS has a built-in test capability to detect and display
critical failures. It monitors the arm-based electronics, displays
and controls, and the MCIU software checks in the computer monitor
computations. Failures are displayed on panel A8U and on the CRT
and are also available for downlinking through orbiter telemetry.
All of the major systems of the ABE are monitored by BITE. The
MCIU checks the integrity of the communications link among itself
and ABE, displays and controls, and the orbiter computer. It also
monitors end effector functions, thermistor circuit operation
and its own internal consistency. The computer checks include
an overall check of each joint's behavior through the consistency
check, encoder data validity and end effector behavior as well
as the proximity of the arm to reach limits, softstops and singularities.
The white auto 1, auto 2, auto 3, auto 4, opr cmd, test, orb
unl, end eff, orb ld, payload, single and direct lights on panel
A8U indicate the current RMS operating mode.
The software stop talkback indicator on panel A8U indicates gray
when a stop has been commanded by the computer. Barberpole indicates
a software stop has occurred, at least one joint has reached its
limit of travel, and the computer has commanded arm motion to
The rate meter on panel A8U reads in feet per second. Act indicates
the translational speed, and cmd indicates the computer-commanded
The rate min talkback indicator on panel A8U indicates on when
the RHC vernier speed has been selected. Off indicates that the
RHC coarse speed has been selected.
The rate hold talkback indicator on panel A8U indicates on when
rate hold has been commanded and implemented by the computer.
Off indicates that the rate hold function is not in effect. The
rate hold function is engaged or disengaged by the rate hold button
on the RHC.
The 11 RMS C/W annunciators are located on panel A8U. The red
MCIU light indicates the MCIU has failed a self-test. The red
derigidize light indicates that the end effector has derigidized
without command. The red ABE light indicates that a failure has
occurred in the ABE of any joint. The red release light indicates
that the end effector has released the grapple fixture without
command. The red GPC data light indicates invalid data were transmitted
from the orbiter computer to the MCIU and were detected by the
MCIU BITE. The yellow check CRT light indicates an RMS failure
message is on the orbiter CRT. The yellow contr err light indicates
the presence of abnormal conditions in an arm joint that may not
be detected by BITE and may cause a joint runaway (software automatically
applies the brakes when such a condition occurs). The yellow reach
limit light indicates that one of the joints is close to its travel
limit. The yellow stbd temp light indicates that the temperature
of the starboard arm has exceeded its predetermined caution threshold.
The yellow port temp light indicates the same for the port arm.
The red master alarm push button light indicator on panel A8U
signals the RMS operator that an RMS C/W light was activated.
A tone is activated with the master alarm light. The master alarm
light and tone can be canceled by depressing the master alarm
push button indicator. The RMS C/W tone volume can be adjusted
on panel A8U. The C/W tone and master alarm on panel A8U are not
associated with the orbiter's C/W system.
The three digital LEDs on panel A8U display data that are determined
by the parameter rotary switch on panel A8U. A small red light
above each digital LED, when illuminated, indicates there is a
malfunction in the corresponding numerical readout.
The test position of the parameter rotary switch lights all of
the RMS displays and lights and sounds the master alarm on panel
A8U. The numeric indicators should display + 22.214.171.124.
The lighting annun-num bright switch on panel A8U fixes the brightness
of all panel A8 lights to a maximum level, while the var position
enables the low, var, med rotary switch to control the brightness
of the panel lights. The panel/inst rotary off, brt switch on
panel A8U controls the integral lighting on the analog meter,
panel nomenclature and electromechanical talkback indicators on
The rate scale talkback indicator on panel A8U indicates gray
when effective scales are as shown on the translation rate meter.
X10 indicates all readings should be multiplied by 10.
If the manipulator arm cannot be restowed for any reason, it
will be jettisoned so the payload bay doors can be closed. There
are four separation points: one at the shoulder and one at each
of the three retention latches. Each separation point is individually
released. The switches for jettisoning the right or left RMS are
located on panel A14.
An RMS jett deadface switch is located on panel A14. When the
switch is positioned to deadface , the electronics of the three
RMS retention latches are deadfaced. The safe position removes
power from the deadface circuits and the ground reset circuits.
The gnd reset position resets relays in the retention latches
if the RMS was jettisoned. The relays are reset on the ground.
The pyro port or starboard RMS arm switches on panel A14 control
the corresponding arm jettison functions. The jett arm, safe,
guillotine switch on panel A14 positioned to safe opens the corresponding
RMS arm circuitry to disable the guillotine and jettison operations.
Positioning the switch to guillotine closes the circuits, which
arm the corresponding guillotine circuits. The arm position enables
power to the RMS jett switch.
The pyro port or starboard RMS jett switches on panel A14 control
the corresponding arm shoulder jettison. The jett arm, safe, guillotine
switch on panel A14 positioned to safe opens the jettison logic
circuitry for the corresponding arm. Positioning the switch to
guillotine allows power to the guillotine logic circuitry, guillotining
the corresponding arm shoulder wire bundle (the corresponding
RMS arm switch must be in the guillotine position). The wire bundle
is severed by a redundant pyro-operated guillotine. Positioning
the switch to jett allows power to the jettison logic circuitry,
jettisoning the corresponding arm shoulder (the corresponding
RMS arm switch must be in the jett position). The separation system
has redundant pyro-operated pressure cartridges to force a retractor
down and pulls four overcenter tie-down hooks back, which releases
the arm at the shoulder joint support.
The pyro starboard or port retention latches, fwd, mid, aft switches
on panel A14 control the corresponding arm retention latches.
Positioning the switches individually to the safe position opens
the jettison logic circuitry for the corresponding retention latch.
Positioning the switches to guillotine individually allows power
to guillotine the corresponding retention latch. Positioning the
switches to jett individually allows power to the jettison circuitry,
jettisoning the corresponding latch. The separation of the retention
latches operates in a similar manner as the jettisoning of the
shoulder joint. The separation system imparts a minimum impulse
velocity on the RMS arm.