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Payload 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 by telemetry.

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 computers.

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 sequence.

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 cease.

The rate meter on panel A8U reads in feet per second. Act indicates the translational speed, and cmd indicates the computer-commanded speed.

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 + 8.8.8.8.

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 panel A8.

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.


Curator: Kim Dismukes | Responsible NASA Official: John Ira Petty | Updated: 04/07/2002
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