Patent Description:
Many satellites currently in operation were designed with a finite amount of propellant and were not designed for the possibility of being resupplied with propellant. The design philosophy relied upon replacement of the satellites after they had exhausted the on-board propellant supply. In view of the expense of replacing satellites, it would be very advantageous to be able to resupply satellites with propellant which are either near their end of propellant life but otherwise functional, or have suffered an insertion anomaly, or have been maneuvered more than originally intended for their nominal operations, thereby extending their operational life by several or many years. It is estimated that as many as half of all GEO communication satellites end their <NUM> to15 year life with all or most of their subsystems still functional and it is only the depletion of the carefully budgeted propellant load that drives retirement of the satellite. Using a current economic model, the ability to resupply these end of life satellites in one mission with propellant, would extend each of their useful lives by <NUM> to <NUM> years and thereby delay the need to outlay the very high capital costs to launch a replacement for each satellite. Some satellites suffer from primary propulsion system failures or launch vehicle upper stage related failures soon after they are launched. In these cases the entire book value must be written off and compensation paid to the operator by the insurer. The satellite becomes an asset of the insurer and will eventually have to be disposed of in a graveyard or re-entry orbit. If one of these assets can be resupplied with propellant, enabling it to transfer to an orbital station in geosynchronous orbit and extending its life by <NUM> to <NUM> years, most or all of the value of the spacecraft can be recovered.

In addition, new long duration satellite concepts are being proposed where a modular satellite consists of an underlying structure supporting power generation, guidance and control and payload modules, some or all of which can be exchanged or added to over a lifetime that may be significantly longer than current satellites. These satellites benefit from not only an initial resupply of propellant, but from repeated resupply missions over many years of operation.

The key technical difficulty is that these satellites were not designed for robotic servicing, and it is not generally accepted that such missions are technically possible. Specifically, most satellites are designed with propellant fill and drain valves, (or FDVs), that were intended to be filled once prior to launch and never opened or manipulated again. Thus, accessing these FDVs remotely in-orbit presents several major challenges and would involve several operations, each of which is difficult to accomplish robotically including: cutting and removal of the protective thermal blankets, removal of several lockwires hand wrapped around the valves, unthreading and removing outer and inner valve caps, mating a fuel fill line to the valve nipple, mechanically actuating the valve, and when resupply with propellant is complete, replacing the inner valve cap. On-orbit servicing has been the subject of much study over the past thirty years. The idea of maintaining space assets rather than disposing of and replacing them has attracted a variety of ideas and programs. So far the concept has only found a home in the manned space program where some success can be attributed to the Solar Max and Hubble Space Telescope repair missions, Palapa-B2 and Westar rescue missions and the assembly and maintenance of the International Space Station.

Robotic capture and servicing of operating geostationary spacecraft has never been demonstrated. Until recently there have been no technologies disclosed that can solve the problem of accessing the propellant system of an unprepared satellite for the purpose of replenishing station keeping propellant. The majority of artificial satellites in orbit today were not designed with orbital propellant resupply in mind and access to the propellant system is designed to be accessed by a human on earth before launch. The technologies required to access the client spacecraft's propellant system for the purposes of resupply of propellant still have a very low technology readiness level, and are generally considered to be the main obstacle to a successful servicing mission.

Transferring fuels used for spacecraft propulsion systems from one source to another is very dangerous, due to the corrosive and explosive nature of the liquids involved. For example, inadvertent mixing of fuel and oxidizer in bipropellant systems will cause immediate combustion, so a liquid transfer system for bipropellant-based fuels needs to ensure that no accidental mixing occurs. It would be very advantageous to provide a system of tools that are designed for opening and closing of a variety of types/sizes of satellite FDVs during a propellant resupply operation being conducted on an unprepared satellite, such as but not limited to, removal of the sealing cap assembly, coupling/decoupling of propellant hoses to the client satellite, installation of a new sealing cap assembly to mention just a few.

The FDVs on existent satellites come in several designs, of varying dimensions and operating concepts. Therefore, to maximise the economic benefit of such a propellant resupply system, the minimum number of tools of minimum mass should be carried on any mission to permit the resupply of the widest selection of FDV designs using a single tool. Further mass and operational advantages accrue if various aspects of the refueling tool function can be evaluated and controlled using visual means as opposed to relying upon a host of limited sensors.

A further advantage can be realised if the resupply system can be engaged successfully with the broadest possible arrangement of FDVs on the satellite to be resupplied, this being exemplified by being able to accommodate the smallest possible spacing between FDVs.

<CIT>, discloses a system and method for refueling unprepared satellites from a servicing spacecraft which includes a robotic arm, suitable tools which can be affixed to the end effector of the robotic arm required for accessing, opening and closing the fuel fill valve on the satellite being serviced, storage and retrieval stations on a tool caddy on which the tools and various fuel fill valve caps are stored. Several discreet sockets are included for the different sized components making up the fill drain valve that must be removed prior to the refueling operation and returned post refueling. During engagement with the removable features of the fill drain valve (FDV) the sockets cover the entire part being removed. In addition, this refueling tool could not accommodate the variation of vertical/longitudinal axis position of the removable or actuatable features on the variety of fill drain valves to be serviced.

discloses a system and tool for accessing fill/drain valves during propellant resupply of a client satellite by a servicer satellite. This apparatus uses two to three cam wrenches which fit down over the FDV with one wrench engaging unmovable flats and the other engaging rotatable features of the removable valve components. Advantages of this system is that it provides intrinsic torque balancing via the use of a differential gearbox. The wrenches are also configured to be able to accommodate a range of torque feature sizes and shapes (reaction flats, hex, round with flats, square) and is designed with a 2x torque margin.

Disadvantages of both systems above is there is no sensing of the tool states or valve states due to the valve and tools being generally obscured. The cam wrenches of the latter system work as two opposing pairs operating at two elevations on features of different size, each relying on a complex hinging engagement that is triggered by rotating contact of the cams as they close towards the valve body at the base and the actuation nut higher up. The engagement of both pairs of cam wrenches can only occur simultaneously, as they are driven in opposing directions via a differential that can only generate torque through one pair of cam wrenches acting against the other. The strength of this approach is the ability to accommodate a range of sizes and a range of shapes, as well as intrinsic torque balancing, however this also makes it impossible to determine exactly when or if engagement has begun to occur, hence it is impossible to determine the exact state of FDV features. New information from one FDV supplier indicated excessive rotation of the actuation nut in the opening direction could result in a failure of the actuation nut retention feature and subsequently the unintended removal of the actuation nut and the generation of uncaptured debris. Consequently a new requirement was generated for a maximum rotation of the actuation nut, not to be exceeded. This leads directly to a need for enhanced sensing of the valve states.

Disclosed herein is a system and a device which facilitates on-orbit refueling by teleoperation of FDVs of various designs and dimensions on satellites not originally prepared for on-orbit servicing, through the installation of quick connect safety valves, using vision-based and sensor-based feedback to operate a suite of adaptable and adjustable mechanisms.

The present disclosure provides a suite of supporting tools for preparing a client satellite to be refueled as set out in the appended claims. The suite of supporting tools comprising:.

The tie-down mechanism comprises a receptacle housing secured to the servicing spacecraft having a passive locking mechanism configured to receive the tool retained in the common base and to engage with, and lock, the tie-down mechanism `active-half' of the common base.

The common base and the receptacle housing include visual cues to visually assist the robotic arm aligning the common base with the receptacle housing during operations to insert and lock the common base in the receptacle housing.

The suite of supporting tools may include site preparation tools each of which include a common base and a tool tip attached thereto with each tool tip including a specific device action, the tool tip common structure includes a housing with an interface configured to be bolted to the common base, an internally threaded drive shaft having a portion extending out of the housing which is inserted into the common base to engage one of the two mechanism drive interfaces, an advancing externally threaded rod which is threadably installed in the a portion of the drive shaft located inside the housing, a set of input linkages and a set of output linkages located at the distal end of the common structure, wherein rotation of the drive shaft causes the linear movement of the advancing threaded rod which in turn moves a set of input linkages which in turn cause pivotally connected output linkages forming part of the device action features to pivot about a specific point in the given tool tip causing the device action features to open or close, depending on the direction of motion.

The site preparation tools may include a thermal blanket scissor device, such that the device action features are a pair of cutting shears integrally formed with distal ends of the output pivotally connected output linkages to provide cutting action.

The site preparation tools may include a thermal blanket handling device, such that the device action features are a pair of blanket paddles integrally formed with distal ends of the output pivotally connected output linkages to provide a gripping action for gripping and removing pieces of thermal blanket.

The site preparation tools may include a wire cutter and gripping tool, such that the device action features are a pair of wire cutter shears with wiring gripping features integrally formed with distal ends of the output pivotally connected output linkages to provide a gripping action for gripping and cutting wires.

The suite of supporting tools may include a crush seal removal tool for removing crushed seals produced when the fill/drain valve B-nut is removed, the crush seal removal tool including the common base and attached thereto a crush seal removal tool tip which includes an interface configured to be bolted to the common base, an internally threaded rotatable drive shaft which has a portion which is inserted into the common base to engage one of the two mechanism drive interfaces, an externally threaded plunger partially into the internally threaded drive shaft and reciprocally moveable therein, the plunger having a distal plunger face, including a pair of flex jaw linkages pivotally connected together a pivot point, the flex jaw linkages each having a distal flex jaw tip, the flex jaw linkages extending through openings in cage which is rigidly mounted on tool tip base structure, wherein when the drive shaft is rotated, plunger translates backwards into the drive shaft and while the plunger translates, the pivot point of the flex jaw linkages moves with the plunger causing the flex jaw tips to close and retract making contact with a valve stem of the fill/drain valve and dragging along the fill/drain valve stem, the flex jaw tips become preloaded against the fill/drain valve stem and dragged along until they hook onto the crush seal and pry it loose where it is trapped in the cage between the flex jaw tips and the distal plunger face, and wherein rotation of the drive shaft in the reverse direction opens the flex jaw tips and ejects the crush seal from the tool tip by pushing the plunger face forward and pushing the crush seal out of the cage.

The suite of supporting tools may include a B-nut removal tool, the B-nut removal tool including the common base and permanently attached thereto a B-nut removal tool tip, the B-nut removal tool tip including a tool tip base structure which is permanently attached to the common base, a drive shaft having a portion which is inserted into the common base to engage one of the two mechanism drive interfaces, spring wrench fingers coupled to a distal end of the drive shaft, a collet, having a keyed connection to the spring wrench fingers at the proximal end of the spring fingers allowing only motion along the axis of rotation of the drive shaft, the collet having a slots in the outer diameter of the collet, enclosed in a pin carrier housing, including cam-pins mounted in the pin carrier housing that run in the slots, and the pin carrier housing delayed from rotation by the ratchet disc via preloaded against the pin carrier housing at the ratchet disc interface by the preload spring, where rotation of the ratchet disc is restricted by the key feature between the ratchet disc and the tip base structure, so that in order for the pin carrier housing to rotate with the drive shaft the collet must move axially forward as driven by the cam-pins in the pin slots until the end of the pin slots forcing the collet to close the spring fingers over the B-Nut against the B-Nut hex features and continued drive shaft rotation causing rotation of the pin carrier housing, with the collet enclosing the spring fingers and B-Nut, as the ratchet disc interface preload spring preload force is overcome and allows the pin carrier housing surface with ramp features to repeatedly slide over the ratchet disc surface with ramp features thus unthreading the B-Nut from the FDV and such that reversing the drive shaft rotation retracts the collet and allows the spring fingers to open so that the B-Nut is no longer contained and is able to be discarded.

Embodiments of the mechanism for teleoperation of satellite FDVs will now be described, by way of example only, with reference to the drawings, in which:.

Various embodiments and aspects of the disclosure will be described with reference to details discussed below. The following description and drawings are illustrative of the disclosure and are not to be construed as limiting the disclosure. Numerous specific details are described to provide a thorough understanding of various embodiments of the present disclosure. However, in certain instances, well-known or conventional details are not described in order to provide a concise discussion of embodiments of the present disclosure.

As used herein, the terms, "comprises" and "comprising" are to be construed as being inclusive and open ended, and not exclusive. Specifically, when used in this specification including claims, the terms, "comprises" and "comprising" and variations thereof mean the specified features, steps or components are included. These terms are not to be interpreted to exclude the presence of other features, steps or components.

As used herein, the terms "about" and "approximately", when used in conjunction with ranges of dimensions of particles, compositions of mixtures or other physical properties or characteristics, are meant to cover slight variations that may exist in the upper and lower limits of the ranges of dimensions so as to not exclude embodiments where on average most of the dimensions are satisfied but where statistically dimensions may exist outside this region. It is not the intention to exclude embodiments such as these from the present disclosure.

Embodiments of the refueling tool comprise the following components in reference to the Figures.

<FIG>, <FIG> show a typical geometric arrangement of FDV's <NUM> with minimum spacing. The arrangement is shown if <FIG>, wherein a first pair of FDVs are vertically aligned and <NUM>" apart, and a second pair of FDVs are also vertically aligned and <NUM>" apart. The first and second vertically aligned pairs are spaced <NUM>" horizontally apart in a symmetrical, staggered pattern. Note that at the base of each FDV valve body <NUM> and above the level of mounting screw heads, there are a pair of torque reaction flats <NUM>, the mid plane between the flats being in alignment with one of <NUM> mounting screws. The close spacing of fill drain valves <NUM> as shown in <FIG> creates a limited access envelope through which a refueling tool on the servicing robotic arm can be positioned to access the features on the FDVs <NUM>. <FIG> outlines the relevant features of FDV <NUM>, namely B-nut <NUM> (also known as a valve access cap), actuation nut <NUM>, valve body <NUM> with torque reaction flats <NUM>, mounting flange <NUM> and welded connection <NUM> that is completed at installation. <FIG> is an exploded view of the FDV showing FDV nipple <NUM> and the components which cap the valve, B-nut <NUM> and crush seal <NUM>.

As the mounting hole pattern is equally spaced, each FDV can be installed in one of three possible orientations and the final, installed configuration is not a matter of record. Consequently there are three possible orientations of the torque reaction flats on each valve instance. Each of the three possible orientations would be satisfactory for the technician at initial installation, although some would be more awkward than others and hence less likely, but nonetheless possible. A detailed examination of each possible orientation, in each of the four locations, reveals that an automated system must be able to adapt to the torque reaction flats being either parallel to, or perpendicular to the approach direction of the refueling tool. Relying on only one of these two relative orientations, rather than the possibility of either, results in a system that cannot reliably grip the torque reaction flats of any valve in any possible installed configuration.

Also note there are two separate designs of valve in the arrangement shown, and both the valve body diameter and the across-flats dimension are different between the two designs. This is typical of bi-propellant systems, where the two valve sizes actually differentiate between the fuel circuit and the oxidizer circuit by employing different sizes of threaded connection, such differentiation meant to further reduce the remote risk of accidental mixing by attaching a fueling line to an oxidizer circuit, or vice versa, when fueling on the launch pad. This presents a further challenge to mechanism A <NUM>, the function of which is to register alignment with the valve body and clamp onto the valve body and the reaction flats such that the torque applied by the wrench rotation mechanism can be reacted at the valve body and prevented from transmission to the FDV mounting bracket or welded tube connection <NUM>.

Insurability requires that no single point failures impede mission success; therefore a robotic operator of the refueling payload must be able to confirm successful completion of each task, or have the ability to continue the mission under degraded conditions.

Refueling operations can be categorized into two scenarios:.

An operator should always have a minimum two options for sensing each task, which achieves the following:.

Based on trade studies performed, cameras have been identified as the baseline primary sensing during alignment operations because the only reliable way of confirming alignment to the target FDV is through visual indication. This leads to an open architecture solution, where the tool volume around the FDV is kept open to allow camera viewing access. The same refueling tool vision system-based solution for ensuring initial alignment of the refueling tool to the FDV, when properly implemented with complementary tools, is ideal for continually monitoring the FDV state.

The present disclosure is designed around the primary requirement for the refueling tool vision system-based sensing as the main source of operator feedback to validate that various access, alignment, clamping actions of the refueling tool and rotation states of the FDVs b-nut and actuation nut can be validated, including but not limited to; initial coarse alignment and readiness for registration, successful registration to valve body and torque reaction flats, initial wrench alignment to a hexagonal feature both rotationally and in elevation, successful rotation of a hex feature, confirmation of safety valve acquisition, initial alignment of safety valve coupling nut to FDV, including contact confirmation, and confirmation of safety valve coupling nut advancement on FDV threaded connection.

The implementation of refueling tool vision system-based sensing in geosynchronous orbit requires cameras suitable to the task, the environment and the journey to orbit. Video devices tend to be sensitive to extreme temperature ranges, radiation exposure and other aspects of the environment and require extensive qualification testing to demonstrate suitability for the application. Most video devices are designed for consumer or industrial applications and require additional shielding and/or repackaging or reworking for material substitution to meet requirements for the geosynchronous environment. As such, the range of qualified video devices available to the design is limited, and in particular the highly miniaturised video devices ubiquitous in hand held computers are not now, nor likely in the foreseeable future to be suitable for use in geosynchronous orbit. Qualified devices tend to be large compared to their counterparts in the consumer marketplace.

Managing multiple video streams is also challenging within the environment and requires video switching devices made specifically for the task, thereby representing another overhead to any approach involving a large number of cameras. Thus this design is based on a single operational camera view, with the critical nature of that single camera view requiring that it have a fully redundant backup.

Designing operations for camera views leads directly to a device that must operate almost entirely in the background of the image with respect to the target FDV, such that the FDV features can be seen at all times and the view does not become obstructed or unduly shadowed. For this reason, for example, wrenching with an open end wrench from the far side of the camera view is advantageous over wrenching from above with a socket.

The present disclosure is shown in <FIG> and <FIG>. Refueling tool <NUM> is depicted in the process of servicing one of four FDVs <NUM> arranged in a symmetrical pattern on a typical FDV bracket <NUM>. Note that one of four the FDVs <NUM> is shown part way through a refueling operation, wherein the B-nut has been removed and safety valve <NUM> is about to be installed. Cameras <NUM>, beneath camera shield <NUM> are arranged on camera bracket <NUM> such that each camera has a complete view of the worksite and all interactions between the refueling tool and the target FDV. Alternatively, a prime and redundant camera pair could be implemented with a single lens and a beam splitter, thus affording each camera the ideal view rather than each camera having a view that is compromised for the sake of the other camera.

The cameras shown are representative of visions systems in the broader sense. A complete refueling tool vision system may be as simple as a single camera intended for a human operator, or may comprise a suite of optical sensors including but not limited to cameras, lidar and laser range finders more suitable to an automated, machine vision-based system. Additionally, a single camera may be used in conjunction with a detailed optical survey performed by another tool or apparatus on the robotic arm, such that the camera view relates the tool position to the target FDV within a computer generated 3D rendering. In this sense a refueling tool vision system-based architecture encompasses any optical system used in conjunction with a human or machine operator to validate the successive states of the refueling operation.

Also visible in <FIG> are four contact spheres <NUM>, one on each of two touchdown rods <NUM> and two touchdown arms <NUM>, one of the touchdown rods mounted to camera bracket <NUM> and the other to touchdown bracket <NUM>, the purpose of the contact spheres being to indicate contact between the refueling tool and the FDV bracket <NUM> via force/moment sensing and control or other means within the robotic arm <NUM>. The contact spheres, touchdown rods and arms shown are representative of a means of touchdown sensing and could alternatively employ other technologies including but not limited to proximity sensing and sensing by mechanical actuation of switches by either direct or indirect means.

<FIG> also shows the elements of refueling tool end effector interface <NUM>, namely, grasp fixture <NUM>, first rotary input shaft <NUM>, second rotary input shaft <NUM>, electrical connectors <NUM> and quick connect nipple <NUM>. The refueling tool consists essentially of a collection of mechanisms, each with a specific function, namely, mechanism A <NUM> for registering to and clamping onto valve body <NUM> and torque reaction flats <NUM>, mechanism B1 <NUM> for closing and opening the wrench, mechanism B2 <NUM> for rotation of the wrench, mechanism C <NUM> for elevation adjustment of the rotating wrench, and mechanism D <NUM> for connection of the refueling system to the nipple of the target FDV. Each mechanism requires one independent actuation, except for mechanism D which requires two.

Mechanism B1 for closing and opening the wrench is compliantly mounted to mechanism B2 for wrench rotation, which is in turn is mounted to mechanism C for wrench elevation. Mechanism A for registration and clamping onto the valve body is also mounted to mechanism C. This sub-structure forms the torque reaction loop that ensures torque induced by rotating the wrench is reacted at the valve body via the torque reaction flats, as required. This sub-structure is connected to mechanism D, which includes the refueling delivery system and refueling tool top plate <NUM>, which includes the end effector interface by bolted and pinned connections to side plates <NUM>, thus forming the complete refueling tool assembly or structure.

Requiring a high number of separately controlled actuations could be considered a detriment to this design approach, particularly if each requires a discrete actuator, as drive electronics for the discrete actuators may reside on the robotic arm, with the associated interconnections passing separably through the electrical connectors of the end effector of the robotic arm and the refueling tool.

The end effector of the robotic arm optimally has two external tool drives, since the majority of tools used in the complete refueling operational concept are passive, externally driven devices requiring one tool drive input for stowing and un-stowing and a second tool drive input for operation of the mechanism, the passive tools (site preparation and refueling support tools discussed herein after) including but not limited to those for cutting and manipulating thermal blankets, cutting and removing lock wire and removing B-nuts and crush seals.

In order to minimize the number of discrete actuators, associated drive electronics, and separable electrical interconnections, a power transmission device <NUM> moveably located adjacent to the refueling tool end effector interface is used to selectively direct a first end effector rotary drive shaft <NUM> to one of <NUM> discrete outputs, one for each of mechanisms A, B2, C and D. A second end effector rotary drive shaft <NUM> is used to actuate the transmission device, the actuation being for the purpose of selecting which of the mechanisms to connect to the first tool drive input. The power transmission device may optionally include additional mechanisms to perform additional actuations within the refueling tool, such as stowing and un-stowing of the refueling tool.

Each of the aforementioned mechanisms, and other elements of the current disclosure are further described in the paragraphs below.

Referring to <FIG>, <FIG> and <FIG> and <FIG>, mechanism A is driven in a closing motion by clockwise rotation of input shaft <NUM> supported between lower thrust ball bearing <NUM> and upper thrust needle roller bearing <NUM>, the former selected for the high thrust loads induced by mechanism A clamping and the latter for the comparatively low thrust loads involved in driving the mechanism through free space to the fully open position. Clockwise rotation induces upwards motion of tension assembly <NUM> comprising tension housing <NUM>, lead nut <NUM>, piston <NUM> with cross pin <NUM>, springs <NUM>, spacers <NUM> and <NUM>, end cap <NUM> and linear bearing rail <NUM>. Cross pin <NUM> passes through slots on both sides of tension housing <NUM>. Linear bearing block <NUM>, mounted to mechanism A frame <NUM>, guides motion of tension assembly <NUM> and maintains alignment with input shaft <NUM>. Springs <NUM>, being positioned between end cap <NUM> and piston <NUM>, allow for continued upwards motion of the tension assembly after the rest of the mechanism has contacted the valve body and stopped moving, such continued motion being used to compress the springs and produce a predetermined level of clamping load.

Vertical motion of the tension assembly induces horizontal motion of pushrod <NUM> via drive links <NUM>, rocker arm <NUM> and connecting links <NUM>, the drive links <NUM> being connected to cross pin <NUM>. Pushrod <NUM> is guided within bushing <NUM> which is contained within mechanism A frame <NUM>. Mechanism A frame <NUM> forms the structural framework for aligning the refueling tool <NUM> to the FDV axis <NUM> via mechanism A mounting interface <NUM>.

Mechanism A jaws <NUM> rotate on pivots <NUM> housed within body <NUM>, and are driven to close symmetrically by rollers <NUM> contained within roller bracket <NUM>, as the roller bracket is driven forward towards the target FDV by virtue of its connection to pushrod <NUM>. Rollers <NUM> run inside closed slots within jaws <NUM> such that the rollers drive the jaws both in the close direction and in the open direction, the closed slots being shaped to produce a closing motion that is fast in the region of stroke allotted to centring, then much slower within the region of stroke devoted to clamping, this latter region designed to accommodate FDV bodies of various sizes and orientations. The slower closing motion within this region of stroke devoted to clamping affords a better mechanical advantage to the roller bracket <NUM>.

Jaws <NUM> are each equipped with two grippers <NUM> which are free to rotate through approximately <NUM> degrees. Each gripper has two contact fingers <NUM> and as the jaws close around the base of FDV <NUM> one finger from each gripper will contact the cylindrical surface and the other the torque reaction flat <NUM> on valve body <NUM>. This arrangement allows the grippers to close around a range of valve body diameters in two distinct orientations; with torque reaction flats parallel to the mechanism A pushrod and with torque reaction flats perpendicular to the mechanism A pushrod as depicted in <FIG>,.

Prime and redundant microswitches <NUM> mounted to tension assembly <NUM> change state from closed to open when springs <NUM> have reached the desired compression, the switches informing the operator of the latched condition.

Referring to <FIG>, <FIG>, <FIG>, <FIG>, <FIG>, <FIG>, mechanism B1 is a wrench close/open device based on twin lead screws <NUM> with right hand thread and left-hand thread on opposing ends, in a parallel screw clamp arrangement such that similarly handed threads are on each side of the assembly with right hand threads on the actuator side. Two wrench jaws <NUM>, each housing two similarly handed lead nuts <NUM>, are mounted onto the corresponding lead screw threads on each side of the mechanism B1, the wrench jaws being configured such that the location where the wrench jaws intersect the FDV axis <NUM> lies on a line formed by the lead screw centres. Each lead nut <NUM> is retained by nut clamp <NUM>, the lead nut being free to rotate within the wrench jaw and the nut clamp during initial setup in order to establish a parallel arrangement of the wrench jaws. The lead nuts are locked from rotation thereafter by drilling holes through the nut clamps, lead nuts and wrench jaws and installing locking pins <NUM>.

The need for B1 actuation to be independent of other mechanism motion, most notably wrench rotation, combined with the complexity of motion of the B1 actuation axis, provides ample justification for a discrete actuator for this mechanism.

Mechanism B1 housing <NUM> and B1 cover <NUM> enclose and locate the central gear <NUM> of each lead screw via bearings <NUM>, one in each of the housing and cover and two idler gears <NUM> via idler shaft <NUM> and idler bearing <NUM>. B1 drive input gear <NUM> is supported via a pair of bearings <NUM> located side by side within the cover, thereby permitting the axis of the drive input gear to be exposed through an opening in the B1 housing. Referring to <FIG>, the B1 drive input gear has, on the exposed drive axis, a torque reacting recess <NUM> precisely manufactured to accept torque reacting shaft <NUM> of B1 drive actuator <NUM>, the torque reacting recess in this embodiment being in the form of a shaft with a flat. The mechanism B1 housing <NUM> provides a unique mounting arrangement for B1 drive actuator <NUM>, which is coaxially mounted to a puck-shaped adaptor <NUM> made of self-lubricating material. This adaptor is located and contained within a corresponding recess <NUM> in the mechanism B1 housing <NUM>, and retained therein by two retaining clips <NUM>. The adaptor is fitted with two pins <NUM> oriented radially on opposing sides of the adaptor such that the pins are coaxial. B1 housing actuator recess <NUM> has cut-outs to accommodate the radially opposed pins and to allow for rotation of the actuator adaptor with the pins on the order of <NUM> degrees. Two spring plunger assemblies, each comprising a post-mounted plunger guide <NUM>, compression spring <NUM> and plunger <NUM> with bifurcated head <NUM> are arranged tangentially to the B1 housing actuator recess <NUM> with the bifurcations straddling the radially opposed pins such that both spring plunger assemblies exert a counter-clockwise torque on the actuator adaptor as viewed from the end of the actuator opposite to the actuator shaft. The torque forces the radially opposed pins to be seated against one end of the B1 actuator recess cut-outs and collectively the fit and retention of the actuator adaptor within the B1 actuator recess in conjunction with the arrangement of spring plunger assemblies allows the actuator mounted on the adaptor with the radially opposed pins to rotate clockwise within the B1 housing actuator recess in opposition to the tangentially arranged spring plungers when the wrench jaws have closed on an object or have reached the end of travel in the closed direction.

One of the spring plungers with bifurcated head <NUM> interacts with a pair of microswitches <NUM> such that the switches are closed when the spring plungers are fully extended, becoming open as the spring plungers are compressed, the actuator being commanded to stop when the microswitches change to the open state. This arrangement causes the actuator to shut off at a predetermined torque value regardless of position within the mechanism stroke, the torque value being determined by the selection of springs for the spring plungers.

Shoulder bolts <NUM> installed through the wrench jaws into the B1 housing and B1 cover define travel limits of the wrench jaws in the closed direction.

Two mounting lugs <NUM> on B1 housing <NUM> provide a means for attachment.

Residual misalignment between the refueling tool wrench rotation axis and the FDV axis after clamping onto the FDV body could induce side loads on the FDV when the wrench is clamped onto the FDV, and also when the wrench is rotated. In order to minimize the side loads, a small range of spring-centred compliance is afforded by the compliance mechanism, in both radial and tangential directions.

Referring to <FIG>, <FIG>, <FIG> and <FIG>, a rectangular coupling platform <NUM> features a coaxial pair of protruding lugs <NUM> along each of two parallel first edges on the upper side of the platform such that each lug is near a platform corner. A similar arrangement of coaxial pairs of protruding lugs <NUM> is similarly placed on the underside of the platform along two edges that are perpendicular to the first edges, the first edges being oriented radially with respect to the workspace of the FDV and the second edges being oriented tangentially with respect to the workspace. Ball bushings <NUM> are fitted into the protruding lugs on both sides of the platform, the bushings being secured to the protruding lugs by a bushing circlip <NUM> placed at both ends of the ball bushings, the circlips straddling the protruding lugs.

A first pair of precision shafts <NUM> is supported within the ball bushings on the upper side of the platform, one shaft per pair of coaxial pair of bushings, such that at least <NUM> of shaft extends beyond the outward ends of the coaxial pairs of bushings. Coupling bracket <NUM> is mounted onto, and straddles the first pair of precision shafts on the upper side of the platform via a pair of down-swept protrusions <NUM> symmetrically located on each of two sides of the coupling bracket, the pairs of down-swept protrusions being spaced to accommodate length-adjustable locking shaft collars <NUM> between them, the shaft collars being used to secure the coupling bracket to the precision shafts centrally between the pairs of ball bushings, adjustment of the length-adjustable locking shaft collars being used to eliminate free play between the coupling bracket and the first pair of precision shafts. A pair of compression springs <NUM> placed on each of the first pair of precision shafts on the upper side of the platform, each one located between a ball bushing <NUM> and a down-swept protrusion <NUM>, each of the compression springs partially compressed at installation, permit limited, spring-centred bilateral motion of the coupling bracket, shafts and shaft collars with respect to the coupling platform, parallel to the axes of the first pair of precision shafts.

A second pair of precision shafts <NUM> is supported within the ball bushings on the underside of the platform, one shaft per pair of coaxial pair of bushings, such that at least <NUM> of shaft extends beyond the outward ends of the coaxial pairs of bushings. Mechanism B1 <NUM> is mounted onto, and straddles the second pair of precision shafts via B1 mounting lugs <NUM>. The mounting lugs are secured to each of the second pair of precision shafts via two length-adjustable locking shaft collars <NUM> per shaft, one on either side of each of the mounting lugs, at a central location on the shafts, adjustment of the length-adjustable locking shaft collars being used to eliminate free play between the mechanism B1 and the second pair of precision shafts. A pair of compression springs <NUM> placed on each of the second pair of precision shafts on the lower side of the platform, each one located between a ball bushing <NUM> and a length-adjustable locking shaft collar <NUM>, each of the compression springs partially compressed at installation, permit limited, spring-centred bilateral motion of the mechanism B1, shafts and shaft collars with respect to the coupling platform, parallel to the axes of the second pair of precision shafts. Torque cell <NUM> is mounted between coupling bracket <NUM> and torque cell plate <NUM>, the torque cell plate including the mounting interface <NUM> of the compliance mechanism to the mechanism B2.

Mechanism B2 is a wrench rotation device designed to rotate wrench close/open mechanism B1 through a hard stop limited arc of <NUM> degrees in either the clockwise or counter-clockwise direction, thus achieving one full turn of a hexagonal feature in six increments by repeatedly closing and opening the B1 mechanism in concert with back and forth rotation through <NUM> degrees, the extra <NUM> degrees being a buffer between commanded motion and end of travel. Incremental rotation allows for the mechanism to occupy primarily one side of the volume surrounding the FDV axis, thus permitting a clear view of the overall operation via cameras situated on the opposite side of the volume.

Referring to <FIG> and <FIG>, <FIG> and 13A and 13B, segment gear assembly <NUM>, comprising segment gear <NUM>, end-of-travel pin <NUM>, segment gear carrier <NUM>, a first pair of track rollers <NUM> and tensioner assembly <NUM>, itself comprising a second pair of track rollers <NUM>, tensioner yoke <NUM>, tensioning screw <NUM> and disc springs <NUM>, is constrained to rotate about wrench rotation axis <NUM> via contact and preload between precision rolling surfaces <NUM> of rotation track plate <NUM> and the first pair and the second pair of track rollers, the former in contact on the outer precision rolling surface and the latter on the inner, the precision rolling surfaces being sufficient in arc to allow plus and minus <NUM> degrees of rotation of the segment gear assembly about a central position, with a thickening of the rim formed by the precision rolling surfaces beyond the arc forming travel stops, the wrench rotation axis being defined by the precision rolling surfaces.

Mechanism B2 drive housing <NUM> supports lead nut <NUM> and nut clamp <NUM>, the lead nut being locked against rotation within the B2 drive housing and the nut clamp by locking pin <NUM>. B2 drive gear <NUM> with internally-splined hub <NUM> is supported via bearings <NUM> housed in the B2 drive housing and the rotation track plate. The segment gear assembly is constrained along the wrench rotation axis by segment gear bumper <NUM> and thrust pad <NUM>, the former mounted to the rotation track plate and the latter to the B2 drive housing.

Pairs of microswitches <NUM> separated by microswitch spacers <NUM> are mounted in stacked configurations via slots in the rotation track plate near each end of the range of motion of the end-of-travel pin mounted within the segment gear, the slots permitting the adjustment of the stacked pairs of microswitches such that they change from a free state to an operating state to signal an end to rotation in advance of the travel-limiting thickening of the rim formed by the precision rolling surfaces. Elevation travel indicator <NUM> is mounted to the rotation track plate.

Mechanism C is an elevation stage for the wrench rotation mechanism B2 which requires mechanism B2 to be present in order to function as a mechanism. Consequently, <FIG> depicts mechanism C parts alone, while <FIG>, from the same perspective, includes mechanism B2 for clarification. Referring to these figures, and <FIG> from a different perspective, back plate <NUM>, including interface to mechanism A <NUM>, and mid plate <NUM> are secured together and form a basis for the RT structural frame. A pair of linear bearing rails <NUM> are secured to the inward-facing side of the back plate oriented vertically and widely spaced on the back plate. A pair of linear bearing blocks <NUM> are precisely guided on each of the linear bearing rails. Right angle brackets <NUM> are mounted to the linear bearing blocks, one per the block and arranged like bookends, such that each pair of the brackets straddle and support rotation track plate <NUM> of mechanism B2 <NUM>. A pair of non-metallic bumpers <NUM> mounted to the back plate at each end of each of the linear bearing rails define the limits of travel.

A pair of retracted microswitches <NUM> is mounted via slots in the back plate, near the upper end of travel of elevation travel indicator <NUM> of mechanism B2 <NUM>, the slots permitting the adjustment of the retracted microswitches such that they change from a free state to an operating state to signal an end to mechanism C motion in the upwards direction prior to contact with the non-metallic bumpers. A pair of extended microswitches <NUM> is similarly mounted via slots in the back plate, near the lower end of travel of elevation travel indicator <NUM>, the slots permitting the adjustment of the extended microswitches such that they similarly signal an end to mechanism C motion in the downwards direction prior to contact with the non-metallic bumpers. It will be appreciated that the present system and tools uses sensing means that are microswitches but it will be appreciated other types of sensors may be used, a non-limiting example being potentiometers.

Bearings <NUM> mounted within mid plate <NUM> support mechanism B2 spline shaft <NUM> and mechanism C lead screw <NUM>, the spline shaft aligning and interfacing with internally-splined hub <NUM> of B2 drive gear <NUM>, thus transferring torque to the B2 drive gear regardless of mechanism C position, the lead screw aligning and interfacing with lead nut <NUM> of mechanism B2 <NUM> in order to drive mechanism C through its range of motion.

Mechanism D <NUM> is used to connect the refueling system to the FDV nipple <NUM> via the installation of a safety valve <NUM>. The safety valve <NUM> is a non-latching quick connect device with a secondary check valve and is designed to be mounted to an FDV permanently in place of the B-nut after the B-nut has been removed. Once installed, it acts as a safe fluid coupling to pass fuel or oxidizer through a FDV into the client spacecraft, providing two independent seals against leakage beyond the seat of the actuation nut of the FDV, which is itself the primary seal in the line. Referring to <FIG>, the safety valve <NUM> comprises a valve body <NUM> with external capture groove <NUM>, coupling nut <NUM> and spring <NUM>, the valve body featuring a fully independent check valve <NUM> and a quick connect nipple <NUM> which is essentially another check valve that is either forced open by the act of coupling or by the application of pressure via flowing gas or liquid after coupling.

The quick connect coupling and nipple are of a non-latching variety. Specifically, unlike the vast majority of quick connect systems in common usage, known as latching quick connects, which latch together via the interaction of detent balls and a groove, the locking action being released by the axial movement of a spring-loaded external locking collar, the non-latching quick connect coupling and nipple require an externally applied force to maintain the connection of the coupling and nipple. A latching quick-connect coupling design could be adopted in another embodiment, though the latching function is superfluous when used with the refueling tool as presented here.

The safety valve <NUM> is designed to be installed on the FDV after removing the b-nut and prior to passing fuel or oxidizer. Once fuel or oxidizer is transferred through the safety valve <NUM>, the safety valve <NUM> is left on the client valve. The quick connect coupling on the safety valve <NUM> enables subsequent refueling operations of the client satellite <NUM> at later points in time to be more quickly and safely performed, with the refueling operation no longer requiring the removal or re-installation of the b-nut or the actuation of the valve actuation nut to open or close it, with the added advantage that leakage outboard of the valve actuation nut is now being mitigated through the check valve and quick disconnect coupling.

As shown in <FIG>, Mechanism D <NUM> features two independent coaxial actuations of two carriages; hereafter referred to as D1 actuation and D2 actuation. Mechanism D2 actuation is dedicated to capturing and holding onto the safety valve and thereafter the ability to mate and de-mate the propellant delivery system of the robotic arm to the safety valve via actuation of a quick connect coupling <NUM> in order to force together the coupling and the nipple. Mechanism D1 actuation is dedicated to acquisition of and manipulation of the safety valve along the FDV axis in order to remove it from a storage location and install it on an FDV, the height of the FDV being dependent on the variety of FDV being accessed. The D2 actuation results in motion between mate/de-mate carriage assembly <NUM> and safety valve carriage assembly <NUM>. The mechanism D1 actuation results in motion between the safety valve carriage assembly and mechanism D baseplate <NUM>, the safety valve carriage assembly carrying all components of the D2 actuation, the D1 and D2 actuations being along the FDV axis in both a first direction and a second direction, the first direction being towards the FDV and the second direction opposite to the first direction.

The current embodiment uses a discrete actuator for the D2 actuation. Optionally the D2 actuation could be performed by an additional mechanism within transmission <NUM>.

Referring to <FIG> & <FIG>, a first set of linear guide rails <NUM> is mounted to the mechanism D base plate <NUM>, along with, four (<NUM>) adjustable end stops <NUM>, and two dual microswitch assemblies <NUM>, the microswitch assemblies acting to limit the commanded motion of the safety valve carriage assembly. Each of the dual microswitch assemblies includes advance microswitch <NUM> and retract microswitch <NUM>.

The safety valve carriage assembly includes safety valve carriage <NUM> with two locking arm posts <NUM> along the edge of the safety valve carriage closest to the FDV and symmetrically spaced about the FDV axis, the posts forming short-stroke rotation centres for two symmetrical safety valve locking arms <NUM>, mounted on flanged bushings <NUM>, the distal ends of the locking arms being shaped to collectively form a diameter compatible with the external capture groove of the safety valve body, the locking arms each including a precisely shaped actuation slot <NUM> on the side adjacent to the mate/de-mate carriage assembly. Linear guide blocks <NUM>, safety valve sensor assembly <NUM>, compliant coupling assembly <NUM>, first actuation actuator <NUM>, microswitch striker <NUM> and a second set of linear guide rails <NUM> are all mounted to the safety valve carriage, the linear guide blocks maintaining precise alignment to the mechanism D base plate via the first set of linear guides.

Mate/de-mate carriage <NUM> forms the platform for the mate/de-mate carriage assembly and includes two track rollers <NUM> symmetrically spaced about the FDV axis along the edge closest to the FDV, the track rollers residing in the actuation slots of the locking arms such that relative motion between the mate/de-mate carriage assembly and the safety valve carriage assembly in the first direction causes the locking arms to swing towards each other and to fit precisely within the external locking groove of the safety valve, the precision slots being shaped to produce first a rapid closing motion to the closed position and thereafter to maintain the locking arms in the closed position while allowing continued motion of the mate/de-mate carriage assembly, the continued motion being optionally exercised only when attempting to fully mate the quick connect coupling and nipple.

Also mounted to the mate/de-mate carriage are linear guide blocks <NUM>, lead nut <NUM>, quick connect coupling <NUM>, manifold <NUM> with travel stop <NUM>, and dual microswitch assembly <NUM>, the linear guide blocks ensuring precise alignment between the mate/de-mate carriage assembly and the safety valve carriage assembly via the second set of linear guides, the lead nut completing the connection to the mechanism D2 actuator, the dual microswitch assembly interacting with the microswitch striker to signal the end of travel in the first direction.

Relative motion of the mate/de-mate carriage assembly with respect to the safety valve carriage assembly in the second direction correspondingly de-mates the quick connect coupling and nipple if mated and then fully releases the safety valve.

The shape of the actuation slots in the locking arms ensures that the commanded motion of the mate/de-mate carriage with respect to the safety valve carriage can only be completed when the shaped ends of the locking arms coincide with the external locking groove of the safety valve, the external locking groove of the safety valve being shaped with generous lead-in to assist with the alignment. Excessive misalignment causes the locking arms to close around the outer diameter of the safety valve instead of the external locking groove, causing the D2 actuation to stall and preventing the mate/de-mate carriage from completing the commanded motion, the commanded motion being aborted by a current limit on the D2 actuation.

To further assist in the alignment of the locking arms with the external locking groove of the safety valve, the D2 actuation is triggered by safety valve sensor assembly <NUM> comprising sensor housing <NUM> and sensor base <NUM>, both of a self-lubricating material, trigger plate <NUM>, prime and redundant ready-to-latch microswitches <NUM>, compression springs <NUM> and limiting pin <NUM>, the compression springs selected to be installed with preload and final load chosen in consideration of robotic arm performance, force-moment sensing capabilities and/or techniques if any, and FDV load limits, the limiting pin acting within a slot within the housing, the slot commensurate in length with microswitch stroke. The microswitches, in contact with one side of the trigger plate, change state when contact between the opposite side of the trigger plate and the top surface of the safety valve result in motion of the trigger plate sufficient for the indication.

Flexible hose <NUM> is also shown in <FIG> and on the opposite side of mechanism D baseplate <NUM> and includes a right angle fitting which passes through a slot in the baseplate to form a connection with manifold <NUM>.

The D1 actuation, between mechanism D base plate <NUM> and safety valve carriage assembly <NUM>, is accomplished via rotation of splined input shaft <NUM> which drives safety valve lead screw <NUM> via gears <NUM> and bearings <NUM> housed within drive bracket <NUM>, the drive bracket being rigidly mounted to the mechanism D base plate. Rotation of the lead screw induces linear motion of lead nut <NUM> contained within guide housing <NUM>, the housing supporting guide pin <NUM>, and connecting pins <NUM>, the guide pin and connecting pins forming a connection to compliant coupling assembly <NUM> permitting limited, bi-lateral, spring-centred compliance between the safety valve carriage and the D1 actuation, the compliance afforded by the action of shuttles <NUM> and springs <NUM> contained within compliance housing <NUM> and compliance base <NUM>, both made of a self-lubricating material.

Compliance microswitch <NUM> mounted to the guide housing and interacting with compliance striker <NUM> mounted to the safety valve carriage, changes state when motion of the safety valve carriage assembly in the first direction is arrested by contact between the safety valve and the FDV, the change of state signaling an end to forward motion. Thus the compliance microswitch serves effectively as a touch sensor to indicate readiness for safety valve installation.

The transmission <NUM> is used to selectively direct a first end effector tool drive input to one of <NUM> drive outputs <NUM>, each of the drive outputs being a rotating gear with an internally-splined hub <NUM>, the internally splined hubs being compatible in size and relative position with the splined input shafts of the mechanisms A, B2, C and D.

Referring to <FIG>, transmission housing <NUM>, top cover <NUM> and bottom cover <NUM> enclose and support transmission gears <NUM> arranged in <NUM> distinct layers, each of the layers designed to transfer torque from an input gear <NUM> to an output gear <NUM>, the input gear of each layer being arranged on a common axis <NUM>. Each of the input gears features an internally splined hub <NUM> and is supported on a bearing <NUM> within a support housing <NUM>. The input gears, each with the bearing and support housing, and thrust washers <NUM> are arranged in a stack within the transmission housing, and contained by the top and bottom covers, such that one of the thrust washers is between the bottom gear in the stack and the bottom cover and one of the thrust washers is between each successive gear and the support housing beneath it and one of the thrust washers is between the support housing of the top gear and the top cover. Remaining gears, including the output gears, are straddle mounted on two bearings <NUM>, one bearing in the transmission housing and the other in one of the top and bottom covers.

The transmission is moveably mounted via mounting bracket interfaces <NUM>. Lead nut <NUM> and nut clamp <NUM> mounted to the transmission housing form the interface by which the transmission is actuated.

<FIG> includes a section view of the stack of the input gears, bearings and support housings, Each of the support housings has the form of a disk with a central hole, with a complete rim <NUM> on the inner diameter and a partial rim <NUM> of approximately <NUM> degrees of arc on the outer diameter, the complete inner rim forming a hollow shaft for the bearing, the partial outer rim forming a cover over the gear teeth of the input gear except for the missing segment, the missing segment of outer rim of the support housing allowing the input gear to mesh with another gear. Visible in <FIG> the outer diameter of the partial outer rim of the support housings are interrupted by three cylindrical grooves <NUM>. The bore <NUM> within the transmission housing which precisely locates the support housings via the outer diameter is also interrupted by a hole <NUM> parallel to the axis of the transmission housing bore and breaking through the cylindrical wall of the bore, such that the axis of each of the grooves on the outer diameter of the support housings can be made to align with the axis of the hole in the transmission housing by rotating the support housing within the transmission housing bore. Locating pin <NUM> fitted within the hole in the transmission housing forms a locating feature along the full length of the bore, such that the support housings can only be installed in one of three rotational orientations, each of the three orientations being determined by one of three the cylindrical grooves, thus ensuring that the outer rim openings of support housings of the input gears maintain alignment with the next gear in each layer. In the current embodiment three grooves are sufficient for four layers of gearing only because two non-adjacent layers share similar output directions. Another embodiment may require one groove per layer of gearing. Additionally, the only reason to include all grooves on all support housings is one of interchangeability. Alternatively, each support housing could be made for a specific layer, with a single groove correspondingly placed.

Each of <FIG> show a section view of the transmission through one of the four layers of gearing. Each layer includes one of the input gears, one or two idler gears and one of the output gears.

<FIG> is a section view immediately below refueling tool top plate <NUM> showing transmission <NUM> mounted on two linear guide rails <NUM> via linear guide blocks <NUM> and transmission brackets <NUM>. The linear guide rails are mounted to transmission support plate <NUM>, the support plate being located and supported between top plate <NUM> and mid plate <NUM> with bolted and pinned connections.

Also shown in <FIG> are linear potentiometer <NUM>, potentiometer bracket <NUM> and potentiometer rod bracket <NUM>. The body of the linear potentiometer, mounted to refueling tool mid plate <NUM> via the potentiometer bracket, remains stationary while the potentiometer rod bracket, mounted to transmission <NUM>, moves with the transmission, thereby reporting the position of the transmission within its range of motion.

<FIG> is a top view of refueling tool <NUM>, showing the elements of refueling tool end effector interface <NUM>, namely; grasp fixture <NUM>, first rotary drive input <NUM>, second rotary drive input <NUM>, electrical connectors <NUM> and quick connect nipple <NUM>. The quick connect nipple is mounted to fuel channel <NUM>, the fuel channel providing a sealed delivery passage to flexible hose <NUM> of mechanism D <NUM>. A breakout section in <FIG> reveals first rotary drive input gear <NUM> transferring the first rotary drive input to quill shaft <NUM> via transfer gears <NUM> and quill shaft drive gear <NUM>, the gears supported and enclosed within transfer housing <NUM>.

<FIG> is a section view of quill shaft <NUM>, quill shaft drive gear <NUM> and the stack of transmission input gears <NUM>. The quill shaft is located and supported at the lower end by bearing <NUM> and bearing retainer <NUM> in mid plate <NUM>. The upper end of the quill shaft is supported by quill shaft external splines <NUM> engaged in corresponding internal splines of quill shaft drive gear <NUM>. A second set of external splines <NUM>, approximately midway along the length of the quill shaft is sized and located to engage with the lowest transmission input gear <NUM> in the stack when the transmission is at the upper end of transmission range of motion <NUM>, the range of motion being sufficient to allow the second external spline to engage with each of four the transmission input gears. A breakout section in <FIG> reveals transmission lead screw <NUM> of second rotary input <NUM> and lead nut <NUM> mounted to the transmission such that the second rotary input can be used to drive the transmission on the linear guides through the range of motion.

<FIG> shows conceptually a dexterous end effector <NUM> with the necessary components for a refueling operation, namely; grasp mechanism <NUM>, first rotary drive socket <NUM>, second rotary drive socket <NUM>, robotically mate-able electrical power and data signal connector drive electrical connectors <NUM>, movable quick connect propellant couplings <NUM> and cameras <NUM>. The propellant couplings <NUM> are connected upstream via hoses to the propellant transfer system <NUM>. Cameras <NUM> provide close-in views of the grasping fixture <NUM> on refueling tool <NUM> prior to grasping by end effector <NUM> and similarly, the grapple fixture <NUM> prior to grasping by end effector <NUM> of any of the refueling support tools (<NUM>, <NUM>) or site preparation tools (<NUM>, <NUM>, <NUM>). In one embodiment of the refueling system, a fiducial mark or machine vision target (not shown) is placed adjacent to grasp fixture <NUM> on top plate <NUM>. This enables the processor <NUM> in computer control system <NUM> to compute the position of the grasp fixture <NUM> based on video stream images of the target obtained from cameras <NUM>. This position can be used to guide the motion of the robotic arm <NUM> by the automatic control system <NUM> to the ready-to-grasp position of the grapple or grasp fixture. Alternatively, a video display of that fiducial mark can be displayed to a human tele-operator, to help them guide the motion of robot arm <NUM> to the ready-to-grasp position. The refueling support tools (<NUM>, <NUM>) and site preparation tools (<NUM>, <NUM>, <NUM>) can be similarly equipped with fiducial marks or targets on common tool base structure <NUM>, adjacent to grapple fixture <NUM>. These cameras <NUM> could also be used to monitor the action of the tool tips of the blanket cutter tool <NUM>, blanket handling tool <NUM>, wire Cutter Tool <NUM>, B-Nut Removal Tool <NUM> and crush seal removal tool <NUM>.

In operation, after the servicer spacecraft <NUM> has captured the client satellite <NUM> with berthing device <NUM> and after the FDV worksite <NUM> has been prepared using the robotic arm <NUM> and supporting tools in a succession of operations to expose the FDV <NUM>, the robotic arm <NUM> then brings refueling tool <NUM> to the FDV worksite <NUM> and into alignment with the selected FDV <NUM> axis, thereafter approaching along the FDV axis to effectively lower the refueling tool <NUM> onto the FDV bracket <NUM>. The refueling tool vision system <NUM> of the refueling tool <NUM> provides the primary means for sensing the correct alignment of the refueling tool <NUM> to the FDV <NUM> and monitoring the approach to the FDV bracket <NUM> until contact between contact spheres <NUM> of the touchdown sensing system and the FDV bracket <NUM> is sensed by force/moment sensing or other means within the robotic arm <NUM> or tool.

Actuation of mechanism A <NUM> then causes the mechanism A <NUM> to close symmetrically around the valve body <NUM> and torque reaction flats <NUM>, bringing the refueling tool <NUM> and the FDV <NUM> into final alignment, thereby clamping onto the valve body <NUM> and the torque reaction flats <NUM>. An operator, using primarily the view from the camera <NUM>, now uses mechanism C <NUM> to lower the wrench jaws <NUM> into position near the mid height of the actuation nut <NUM>, having first confirmed through the view from the camera <NUM> that mechanism B1 <NUM>, for wrench closing and opening, is sufficiently open. Mechanism B2 <NUM>, for wrench rotation, is then adjusted so that the wrench jaws <NUM> are parallel to a pair of flats on the actuation nut <NUM> nearest the middle of the wrench rotation range of motion. Mechanism B1 <NUM> is then commanded in the closing direction. As the wrench jaws <NUM> close, an operator may pause to further adjust wrench rotation or wrench elevation into more precise alignment using mechanisms B2 <NUM> and C <NUM> respectively.

When satisfied that the alignment between wrench jaws <NUM> and actuation nut <NUM> is good by checking the view from the camera <NUM>, an operator commands the wrench jaws <NUM> to fully close, where the closing action stops automatically when the mechanism B1 <NUM> has achieved a preset level of torque as determined by the preload microswitch <NUM> of mechanism B1 <NUM>. Once the actuation nut <NUM> is within the wrench jaws <NUM>, an operator commands a clockwise rotation at a preset level of torque in order to ensure the actuation nut is closed. These activities ensure the actuation nut <NUM> is fully closed prior to any subsequent operations on the FDV <NUM> to prepare it for refueling. After the preset level of torque has been applied, regardless of whether or not the actuation nut <NUM> has rotated, the actuation nut will be released and the wrench jaws <NUM> will be reconfigured into a similar alignment with the B-nut <NUM> at the top of the FDV <NUM> using mechanisms B1 <NUM>, B2 <NUM> and C <NUM> for wrench opening/closing, wrench rotation and wrench elevation respectively. After aligning with and closing on the B-nut <NUM> using the same methodology as just described for the actuation nut <NUM>, mechanism B2 <NUM> is actuated in a counter clockwise direction. Unlike the actuation nut <NUM>, the B-nut <NUM> must rotate for successful completion of this step. Rotation of about one quarter turn is required to ensure sufficient loosening of the B-nut <NUM> by the refueling tool <NUM>, and this is achieved by iteratively closing, then CCW rotation, then opening, then CW rotation of the wrench jaws <NUM>.

The refueling tool <NUM> is then stowed on the servicer spacecraft <NUM> in order to use the B-nut removal tool <NUM> and crush seal removal tool <NUM> to remove the B-nut <NUM> and crush seal <NUM> respectively from the FDV <NUM>. After the B-nut <NUM> and crush seal <NUM> are removed and discarded safely on the servicer spacecraft <NUM> using the B-nut removal tool <NUM> and the crush seal removal tool <NUM>, the robotic arm <NUM> once again acquires the refueling tool <NUM> from its stowed location on the servicer spacecraft <NUM> and uses it to acquire a safety valve <NUM>, also from a stowed location on the servicer spacecraft <NUM>. Using the same approach methodology at the safety valve stowed location, and similarly using mechanism A <NUM> to close around the base of the safety valve stowed location, the safety valve carriage assembly <NUM> of mechanism D <NUM> is commanded to advance until trigger plate <NUM> contacts the safety valve shoulder <NUM>, tripping the ready-to-latch microswitch <NUM>.

The mate/de-mate carriage assembly <NUM> is then advanced causing locking arms <NUM> to close around the safety valve assembly <NUM> and lock into an external locking groove <NUM> of the safety valve assembly <NUM>, with confirmation of the closing action coming from the view from the camera <NUM>. The mate/de-mate carriage assembly <NUM> is further advanced to fully mate the quick connect <NUM> on the safety valve assembly <NUM> to the quick connect coupling <NUM> on the refueling tool <NUM> and as confirmed by the dual microswitch assembly <NUM>.

Thereafter mechanisms B1 <NUM>, B2 <NUM> and C <NUM> are used to align the wrench jaws <NUM> to the flats of the coupling nut <NUM> of the safety valve assembly <NUM>, to close onto the coupling nut <NUM> and to loosen and rotate the coupling nut <NUM> through a predetermined number of rotations in order to release the safety valve assembly <NUM> from the stowage location, where the loosening of the coupling nut <NUM> is accommodated by axial motion of the coupling nut <NUM> afforded by spring <NUM> of the safety valve assembly <NUM>. The safety valve assembly <NUM> is then fully retracted into mechanism D <NUM> by retracting the safety valve carriage assembly <NUM> and as confirmed by the safety valve carriage assembly <NUM> retracted microswitch <NUM>. After transferring the safety valve assembly <NUM> back to the FDV worksite <NUM> and re-registering and re-clamping to the FDV valve body <NUM> and torque reaction flats <NUM>, the safety valve carriage assembly <NUM> with the safety valve assembly <NUM> is commanded towards the FDV <NUM> until the coupling nut <NUM> comes into contact with the FDV <NUM>, the contact being evident in the camera view by compression of the safety valve spring <NUM> as well as being indicated by compliance microswitch <NUM> of mechanism D <NUM>.

Mechanisms B1 <NUM>, B2 <NUM> and C <NUM> are then used to manipulate the wrench jaws <NUM> into position at the coupling nut <NUM>, to close on the coupling nut <NUM>, and to iteratively rotate the coupling nut <NUM> in the CW direction while monitoring the view from the camera <NUM> for progress. The same spring-resisted motion that tripped the compliance microswitch <NUM> to indicate contact between safety valve coupling nut <NUM> and FDV nipple <NUM> ensures there is always a small force acting to push together the threads of the coupling nut <NUM> and the FDV nipple.

Once the safety valve assembly <NUM> has been installed on the FDV <NUM>, thereafter mechanisms B1 <NUM>, B2 <NUM> and C <NUM> are used to align the wrench jaws <NUM> to the actuation nut <NUM> and to loosen and rotate the actuation nut <NUM> through a predetermined number of rotations in order to fully open the actuation nut <NUM> for subsequent fluid transfer. Once fluid transfer is complete from the servicer spacecraft <NUM> through the refueling tool <NUM>, through the check valve <NUM> of the safety valve assembly <NUM> into the FDV <NUM> and thus into the client spacecraft <NUM>, thereafter an operator confirms alignment of the wrench jaws <NUM> to the actuation nut <NUM> and if required, thereafter uses mechanisms B1 <NUM>, B2 <NUM> and C <NUM> to align the wrench jaws <NUM> to the actuation nut <NUM>. The wrench jaws <NUM> are then commanded to rotate the actuation nut <NUM> through a predetermined number of rotations in order to fully close the actuation nut <NUM> after completion of fluid transfer. The mate/de-mate carriage assembly <NUM> is then retracted until the quick connect <NUM> on the safety valve assembly <NUM> is de-mated from the quick connect coupling <NUM> on the refueling tool <NUM> and as confirmed by the dual microswitch assembly <NUM>.

The mate/de-mate carriage assembly <NUM> is then further retracted to fully open the locking arms <NUM> from the external locking groove <NUM> of safety valve assembly <NUM>, with confirmation of the opening action coming from the view from the camera <NUM>. The safety valve assembly <NUM> is left behind on the client spacecraft <NUM> after refueling is complete and the refueling tool <NUM> is subsequently mated to a safety valve fixture <NUM> on the servicer spacecraft <NUM> to purge propellant hose <NUM> and refueling tool <NUM> through the safety valve fixture <NUM> prior to stowing the refueling tool <NUM> on the servicer spacecraft <NUM>.

Referring to <FIG>, support tools <NUM> for refueling are independent tools used for specific steps in the refueling flow. Each of these tools <NUM> has a common tool base structure <NUM> and a specific tool tip, designed for the specific task the tool is required for. The common tool base <NUM> allows for a single robotic interface to a manipulator system with a specific `end-of-arm-assembly', while allowing for several tasks to be accomplished. The common base structure <NUM> is made up of a grapple fixture <NUM>, the grasping interface for the tool designed for robotic grasping by the `end-of-arm-assembly' located in the end effector <NUM> of robotic arm <NUM> mounted on the servicer spacecraft <NUM>, see <FIG>. Based structure <NUM> further includes tool mechanism drive interface(s) <NUM> and <NUM>, used for enacting the functions of a given tool via a drive actuator mechanism that resides on the `end-of-arm-assembly'. In the embodiment described herein there are two (<NUM>) tool mechanism drive inputs, one of which is used to drive the specific tool tip on each of the support tools, and the second to drive a 'tie-down' mechanism for retaining the tool when not grasped by the manipulator system. Base <NUM> includes a tool mechanism gear train <NUM> that transfers the rotation and torque from one of the tool mechanism drive input interfaces to the tool tip driveshaft <NUM> via the tool mechanism gear train interface <NUM>, for actuation of that tip. Base <NUM> includes a tie-down mechanism 'active-half' <NUM>, driven by the second tool mechanism drive <NUM> interface either directly, or in an alternate embodiment through another gear-train transmission to the location of the alternate tie-down mechanism. Base <NUM> includes a structure <NUM> that holds the constituent components of the common base <NUM> together.

The common tool base <NUM> has an interface to the tool tips <NUM>, which are permanently attached to an instance of the common base tools <NUM> at the tool tip to tool base geartrain interface <NUM> and the tool tip bolted interface <NUM>. This interface involves a feature that allows for the transfer of rotary mechanical power from the tool mechanism gear train interface <NUM> to the tool tip drive shaft <NUM>. The main structure <NUM> of the tool tip is rigidly connected to the common tool base <NUM>, in this embodiment through the use of a bolted interface <NUM>.

There are several functions in the refueling operations that are allocated to the support tools. These include site preparation tools which include a blanket cutter to <NUM>, a blanket handler tool <NUM>, and a wire cutter tool <NUM>. The tool tips <NUM> of the three site preparation tools are all similarly designed, whereby they all require a simple scissor-action linkage to perform their function. Refueling support tools include a B-nut removal tool <NUM> and a crush seal removal tool <NUM>. These will each be described below.

Referring to <FIG>, in each of the site preparation tool tips, the blanket cutter <NUM>, the blanket handler <NUM> and the wire cutter <NUM>, the tool tip drive shaft <NUM> is internally threaded and an advancing threaded rod <NUM> is installed in the drive shaft <NUM>. The rotation of the drive shaft <NUM> causes the linear movement of the advancing threaded rod <NUM> which in turn moves a set of short input linkages <NUM> which in turn cause the output linkages <NUM> to pivot about a specific point in the given tool tip causing the device action features to open or close, depending on the direction of motion. These action features are cutting shears <NUM> in the blanket cutter <NUM>, tweezer gripping paddles <NUM> in the blanket handler <NUM> and a shear cutter with gripper feature <NUM> in the wire cutter <NUM>.

Referring to <FIG>, B-Nut removal tool tip <NUM> stages motion into two parts. Initially the collet <NUM> is driven forward by the rotation of the drive shaft <NUM> due to the cam-pins <NUM> that run in slots <NUM> on the collet <NUM> until the spring wrench fingers <NUM> contacts the B-Nut hex <NUM> and/or the cam pins <NUM> reach the end of the collet slots <NUM>. The drive shaft <NUM> then continues to rotate forcing the ratchet disk <NUM> interface to separate, causing the pin carrier housing <NUM> to rotate with the collet <NUM> and spring fingers <NUM>, and in doing so the B-Nut <NUM>, captured by the shape of the closed spring fingers <NUM> is threaded off of the FDV <NUM>. To discard the B-Nut <NUM>, the drive shaft <NUM> is rotated in the opposite direction than previously described. The ratchet disk <NUM> restricts motion of the pin carrier <NUM> in this direction, forcing the collet <NUM> to retract and allow the wrench spring fingers <NUM> to open, thus releasing the B-Nut <NUM>.

The ratchet disc <NUM> controls the rotary motion of the pin carrier housing <NUM> by being keyed <NUM> against rotation with respect to the tool-tip base structure <NUM> while being preloaded against the pin carrier housing <NUM> with a preload spring <NUM>. The ratchet disc surface <NUM> and the mating surface <NUM> of the pin carrier housing <NUM> have mating ramp features. In one direction, where the shallow angled surfaces of the ramps slide against each other motion is permitted, which is rotation of the tool to remove the B-Nut <NUM>, only when the input torque is enough to slide the ramps over each other while under the preload spring <NUM> preload that pushes the ratchet disc <NUM> against the pin carrier housing <NUM>. In the other direction the steep side of the ramps engage and relative motion is inhibited in that direction, allowing the collet <NUM> to move to release the B-Nut <NUM>. The drag in the ratchet disc interface <NUM> allows for axial motion of the collet <NUM> to occur ahead of rotary motion.

Referring to <FIG>, the crush seal <NUM> may be adhered to the FDV valve stem <NUM> and must be removed prior to installing the safety valve <NUM> with a new crush seal <NUM>. To operate the crush seal removal tool tip <NUM> the drive shaft <NUM> rotated, which translates the plunger <NUM> backwards into the drive shaft <NUM>. The drive shaft <NUM> has an internal thread while the plunger <NUM> an external thread where they interface <NUM>. While the plunger <NUM> translates, the pivot point <NUM> of the flex jaw linkages <NUM> moves with the plunger <NUM> causing the flex jaw tips <NUM> to close and retract making contact with the FDV valve stem <NUM> and dragging along the FDV valve stem <NUM>. The flex jaw tips <NUM> are preloaded against the FDV valve stem <NUM> and dragged along until they hook onto the crush seal <NUM> and pry it loose. As the flex jaw tips <NUM> come free from the FDV valve stem <NUM>, the crush seal <NUM> is retained within the cage <NUM> which is connected to the tool tip base structure <NUM> which is in turn connected to the common base <NUM>. Rotation of the drive shaft <NUM> in the reverse direction opens the flex jaw tips <NUM> and ejects the crush seal <NUM> from the tool tip <NUM> but pushing the plunger face <NUM> forward and pushing the crush seal <NUM> out of the cage <NUM>.

Referring to <FIG>, an embodiment of the tool tie-down method is to use a ball lock, quick-disconnect mechanism. This is a tie-down that uses the input mechanical motion from the end effector to enable tie-down and retention on the spacecraft, without the need to have active mechanisms for each tool-tie down. In the event that active tie-down mechanisms are not feasible for all tools on the servicer deck, this tool tie-down method, precludes the need for a second robot arm to provide actuation to tie a supporting tool down while the supporting tool is held by the first robotic arm <NUM>. In this mechanism, once the robotic arm has positioned the tool such that the tie down body on the tool <NUM> is fully engaged within the locking interface on the spacecraft <NUM>, guided by appropriate visual cues <NUM> on the tool and servicing spacecraft and by the arm control software, the secondary tool mechanism drive <NUM> is rotated on the tool. This rotation is transmitted to a spline <NUM> on the lead-threaded drive shaft <NUM> within the spacecraft side receptacle <NUM> by the actuator spline within the tie down body <NUM>. Rotating the drive shaft <NUM> causes the ball lock sleeve <NUM> to advance forcing a plurality of balls <NUM> within the spacecraft side receptacle <NUM> to advance into indentations <NUM> in the tie down body <NUM>, thus retaining the tie down body <NUM> and the attached tool tie-down half <NUM> within the spacecraft side receptacle <NUM>. To provide visual confirmation of the tie-down of the tool a visual cue indicator <NUM> is provided. As the ball lock sleeve <NUM> is advanced a protrusion on the ball lock sleeve <NUM> simultaneously pushes a spring loaded indicator <NUM> within the tool thus exposing more and more of the spring loaded indicator <NUM> as the ball lock sleeve <NUM> advances. The spring loaded indicator <NUM> is clearly marked such that when the ball lock sleeve <NUM> has fully engaged the tie down body <NUM> a visual indication is clearly visible. Disengagement of the tie down is through opposite rotation of the second torque drive <NUM>. Alternate embodiments of the tie-down are possible, including a breech-lock style.

<FIG> shows a servicer spacecraft <NUM> and a client satellite <NUM> to be re-fueled by the servicer spacecraft <NUM>. <FIG> shows a non-limiting exemplary example of a computer control system that may be used to control the actions of the refueling tool <NUM>.

The tool <NUM> disclosed herein for accessing fill/drain valves <NUM> on the client satellite <NUM> may be mounted on the dedicated refuelling or servicer spacecraft <NUM> launched directly from earth. The system also includes the propellant transfer system <NUM> for transferring bi-or mono-propellants from the servicing satellite <NUM> to the client satellite <NUM> as disclosed in <CIT> issued <NUM>-<NUM>-<NUM>, the purpose of which is to provide a propellant transfer system <NUM> (<FIG>) for transferring the propellant which is under a combination of remote teleoperator and computer control. Such a dedicated servicer spacecraft <NUM> may include a spacecraft docking mechanism such as that disclosed in <CIT>.

<FIG> shows those items pertaining to the refueling of the client satellite <NUM> in addition to the refueling tool <NUM>. These include, in addition to the servicer spacecraft <NUM>, the client fill/drain valve(s) <NUM>, a robotic arm <NUM>, an end effector <NUM> coupled to the robotic arm <NUM>, the refueling tool <NUM> releasibly grippable by the end effector <NUM>, the propellant transfer system <NUM>, a movable quick connect propellant coupling <NUM> mounted in the end-effector <NUM>, the propellant outlet hose <NUM> running along arm <NUM>, and a communication system <NUM> to provide the two-way radio link <NUM> to Earth <NUM> (or space station or mother ship-whichever is the location of the teleoperation control). Stowage points are shown for the refueling tool <NUM>, the safety valve fixture <NUM>, the stowage posts <NUM> for the safety valve assembly <NUM>, the supporting tools including the blanket cutter tool <NUM>, the blanket handling tool <NUM>, the wire cutter tool <NUM>, the B-Nut removal tool <NUM>, and the crush seal removal tool <NUM>.

<FIG> shows a berthing device <NUM> with its proximal end rigidly attached to servicing spacecraft <NUM> and its distal end releasibly attached to the client spacecraft <NUM>. In one embodiment, berthing device <NUM> consists of a manipulator arm of equivalent functionality and performance to the robot arm <NUM> and end-effector <NUM>, with a grapple fixture <NUM> (not shown on <FIG>) mounted on the exterior of the client spacecraft <NUM>, compatible for grasping by berthing device <NUM>. In a second embodiment, the berthing device consists of a spacecraft docking mechanism as disclosed in <CIT> with the docking interface described in the patent mounted on the exterior of the client spacecraft. The berthing device is required to establish a sufficiently rigid and load-bearing structural connection between servicing spacecraft <NUM> and client satellite <NUM> prior to beginning refueling operations described in <FIG> and <FIG>. It must be sufficiently rigid that interaction of the robot arm <NUM> and end effector <NUM> and a servicing tool with a surface or feature on the client spacecraft <NUM> does not produce loads which cause material change in the relative position and orientation of the client spacecraft <NUM> with respect to the servicer spacecraft <NUM>.

In addition, the servicer spacecraft <NUM> includes an onboard computer control system <NUM> (<FIG>) which may be interfaced with the tool <NUM>, in addition to a propellant flow control system, shown at <NUM> so that it can drive all the components that are opened and closed during the propellant transfer operations in a selected sequence depending on which mode of propellant transfer has been selected based on the pressure in the client satellite <NUM> propellant tank. With the presence of the computer control system <NUM> interfaced with the propellant flow control system, the propellant transfer process may be autonomously controlled by a local Mission Manager or may include some levels of supervised autonomy so that in addition to being under pure teleoperation there may be mixed teleoperation/supervised autonomy.

An example computing system <NUM> forming part of the propellant resupply system is illustrated (<FIG>). The system includes a computer control system <NUM> configured, and programmed to control movement of the robotic arm <NUM> including the handling and operation of the servicing tools (<NUM>, <NUM>, <NUM>, <NUM>, <NUM> and <NUM>) and safety valve assembly <NUM> through the servicing sequence of tasks shown in <FIG> and <FIG>.

The command and control system <NUM> is also configured to control movement of the robotic arm <NUM> and the end effector <NUM> attached thereto for controlling the action of the refueling tool <NUM> and supporting tools. This may be the same command and control system mentioned above that is interfaced with the flow control system, for example a computer mounted on the servicer spacecraft <NUM> which is programmed with instructions to carry out all operations needed to be performed by the servicer spacecraft <NUM> during approach, capture/docking with the client satellite <NUM> and refueling operations. It may also be a separate computer system.

The satellite refueling system includes a refueling tool vision system <NUM> for viewing the operation of the refueling tool operations on the fill-drain valve. It also includes a robotic vision system <NUM> for the purposes of general robotic situational awareness and monitoring the action of the tool tips of the blanket cutter tool <NUM>, blanket handling tool <NUM>, wire Cutter Tool <NUM>, B-Nut Removal Tool <NUM> and crush seal removal tool <NUM>. It also can be used for worksite registration. For this last function, the robotic vision system is used to determine the location of objects in the general workspace with respect to a command frame of reference on the end effector <NUM>. This location is determined as a position and orientation of an object of interest with respect to a frame of reference at the end effector <NUM>. Objects of interest include the locations of any of the following: refueling tool <NUM>, refueling support tools (<NUM>, <NUM>) and site preparation tools (<NUM>, <NUM>, <NUM>) at their stowage locations on the servicer spacecraft. Other objects of interest include the locations of the FDVs <NUM> on the client spacecraft <NUM>.

Communication system <NUM> is interfaced with the robotic arm <NUM> and configured to allow remote operation (from the Earth <NUM> or from any other suitable location) of the robotic vision system <NUM>, refueling tool vision system <NUM>, the robotic arm <NUM> and hence the refueling and supporting tools. The vision system may include distinct markers mounted on the fluid transfer coupling used to couple the fluid transfer system storage tank and piping system to the fill/drain valve of the client satellite <NUM>, as well as markings on all tools associated with the fluid transfer operation.

These cameras may be used within a telerobotic control mode where an operator controlling the servicing actions on earth views distinct views of the worksite on display screens at the command and control console. In an alternative mode, the position of elements like the fill drain valve may be determined by either a stereo camera and vision system which extracts 3D points and determines position and orientation of the fill-drain valve or other relevant features on the worksite from which the robotic arm holding tools (multi-function tool, refueling tool) can be driven to these locations according the sensed <NUM> degree-of-freedom coordinates.

The stereo camera could also be replaced with a scanning or flash lidar system from which desired <NUM> degree-of-freedom coordinates could be obtained by taking measured <NUM>-D point clouds and estimating the pose of desired objects based on stored CAD models of the desired features or shapes on the refueling worksite. For those applications where the spacecraft was designed with the intention to be serviced, a simple target such as described in Ogilvie et al. (<NPL>) could be used in combination with a monocular camera on the servicing robotics to locations items of interest such as the fill-drain valve <NUM>. Finally, the robotic arm or device <NUM> used to position the device may include a sensor or sensors capable of measuring reaction forces between the tools and the work-site (e.g. fill-drain valves <NUM>). These can be displayed to the operator to aid the operator in tele-operation control or can be used in an automatic force-moment accommodation control mode, which either aids a tele-operator or can be used in a supervised autonomous control mode.

As mentioned above, computer control system <NUM> is interfaced with robotic vision system <NUM>, refueling tool vision system <NUM>, the flow control system <NUM> of the propellant transfer system, and robotic arm <NUM>. Previously mentioned communication system <NUM> is provided which is interfaced with the robotic arm <NUM> and configured to allow remote operation (from the Earth <NUM> or from any other suitable location) of the robotic vision system <NUM> (which can also include the cameras <NUM> in the end effector <NUM>), the refueling tool vision system <NUM>, the robotic arm <NUM>, robotic end effector <NUM>, blanket cutter tool <NUM>, blanket handling tool <NUM>, wire cutter tool <NUM>, b-nut removal tool <NUM>, crush seal removal tool <NUM>, refueling tool <NUM> and the flow control system <NUM> (<FIG>). A system of this type is very advantageous particularly for space-based systems needing remote control.

The end effector <NUM> possesses its own embedded processor (as does the robotic arm <NUM>) and receiving commands from the servicing spacecraft computer. The end effector <NUM> also passes power and data from the central computer through to the refuelling tool <NUM>. The refuelling tool <NUM> does not possess embedded computers/microcontrollers so it receives actuator commands from the computer control system <NUM> upstream via the end-effector <NUM>. The end effector <NUM> embedded processor also receives video signals from refueling tool camera <NUM> as well as telemetry from tool sensors including but not limited to the linear potentiometer <NUM> and microswitches (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> and <NUM>). These sensed values can be used in closed loop control system functions within the end-effector. They are also passed to the command and control system <NUM> for overall on-orbit control and can also be displayed to a human tele-operator on earth or in another spacecraft.

Some aspects of the present disclosure can be embodied, at least in part, in software. That is, the techniques can be carried out in a computer system or other data processing system in response to its processor, such as a microprocessor, executing sequences of instructions contained in a memory, such as ROM, volatile RAM, non-volatile memory, cache, magnetic and optical disks, or a remote storage device. Further, the instructions can be downloaded into a computing device over a data network in a form of compiled and linked version. Alternatively, the logic to perform the processes as discussed above could be implemented in additional computer and/or machine-readable media, such as discrete hardware components as large-scale integrated circuits (LSI's), application-specific integrated circuits (ASIC's), or firmware such as electrically erasable programmable read-only memory (EEPROM's).

As noted above, <FIG> provides an exemplary, non-limiting implementation of computer control system <NUM>, forming part of the command and control system, which includes one or more processors <NUM> (for example, a CPU/microprocessor), bus <NUM>, memory <NUM>, which may include random access memory (RAM) and/or read only memory (ROM), one or more internal storage devices <NUM> (e.g. a hard disk drive, compact disk drive or internal flash memory), a power supply <NUM>, one more of the communications interfaces <NUM>, and various input/output devices and/or interfaces <NUM>.

Although only one of each component is illustrated in <FIG>, any number of each component can be included computer control system <NUM>. For example, a computer typically contains a number of different data storage media. Furthermore, although bus <NUM> is depicted as a single connection between all of the components, it will be appreciated that the bus <NUM> may represent one or more circuits, devices or communication channels which link two or more of the components. For example, in personal computers, bus <NUM> often includes or is a motherboard.

In one embodiment, computer control system <NUM> may be, or include, a general purpose computer or any other hardware equivalents configured for operation in space. Computer control system <NUM> may also be implemented as one or more physical devices that are coupled to processor <NUM> through one of more communications channels or interfaces. For example, computer control system <NUM> can be implemented using application specific integrated circuits (ASIC). Alternatively, computer control system <NUM> can be implemented as a combination of hardware and software, where the software is loaded into the processor from the memory or over a network connection.

Computer control system <NUM> may be programmed with a set of instructions which when executed in the processor causes the system to perform one or more methods described in the present disclosure. Computer control system <NUM> may include many more or less components than those shown.

While some embodiments have been described in the context of fully functioning computers and computer systems, those skilled in the art will appreciate that various embodiments are capable of being distributed as a program product in a variety of forms and are capable of being applied regardless of the particular type of machine or computer readable media used to actually effect the distribution.

A computer readable medium can be used to store software and data which when executed by a data processing system causes the system to perform various methods. The executable software and data can be stored in various places including for example ROM, volatile RAM, non-volatile memory and/or cache. Portions of this software and/or data can be stored in any one of these storage devices. In general, a machine-readable medium includes any mechanism that provides (i.e., stores and/or transmits) information in a form accessible by a machine (e.g., a computer, network device, personal digital assistant, manufacturing tool, any device with a set of one or more processors, etc.). Examples of computer-readable media include but are not limited to recordable and non-recordable type media such as volatile and non-volatile memory devices, read only memory (ROM), random access memory (RAM), flash memory devices, floppy and other removable disks, magnetic disk storage media, optical storage media (e.g., compact discs (CDs), digital versatile disks (DVDs), etc.), among others. The instructions can be embodied in digital and analog communication links for electrical, optical, acoustical or other forms of propagated signals, such as carrier waves, infrared signals, digital signals, and the like.

The present system is also configured for full autonomous operation. A fully autonomous system is a system that measures and responds to its external environment; full autonomy is often pursued under conditions that require very responsive changes in system state to external conditions or for conditions that require rapid decision making for controlling hazardous situations. The implementation of full autonomy is often costly and is often unable to handle unforeseen or highly uncertain environments. Supervised autonomy, with human operators able to initiate autonomous states in a system, provides the benefits of a responsive autonomous local controller, with the flexibility provided by human teleoperators.

The block flow chart shown in <FIG> describes in detail the steps taken by the servicer spacecraft <NUM> when it is engaged with the client satellite <NUM> during refueling operations.

The present disclosure has advantages over previously disclosed systems as outlined below.

First, vision system-based open architecture allows for validation of each successive access, clamping and rotation state of the FDV effected by refueling tool <NUM> in the refueling operation, commanded either by a human tele-operator or automatic control. Validation of a successfully completing each successive manipulation step on the FDV as part of the refueling refueling operation is essential to meeting mission requirements.

Second, vision system-based architecture supports fine adjustment of individual mechanism operations in real time within the mission plan. Each mechanism is adaptable to the FDV worksite such that risk associated with unknown aspects of the as-built configuration, such as the orientation of torque reaction flats or variation in mounting tolerances are mitigated, and a variety of different worksites can be serviced with a single tool.

Third, the means for registering to and clamping onto an FDV allows for one refueling tool to adapt to a range of FDV sizes and all possible installation orientations. Detailed consideration of the FDV worksite has revealed that this adaptability is essential to ensuring mission success.

Fourth, the wrench mechanism, comprising those mechanisms for opening and closing, rotating and elevation adjustment of the wrench, can be adjusted to a range of FDV sizes and all possible installation configurations and can perform wrenching operations all while not obstructing the vision system, critical to being able to validate that the manipulation step has been successfully achieved.

Fifth, the use of a safety valve with a quick connect nipple provides two independent means of sealing the FDV after a refueling operation. The combination of a quick connect nipple and a second separate, check valve in series within the safety valve restores the two levels of sealing that were present prior to servicing.

Sixth, the use of a safety valve with a quick connect nipple facilitates successive, greatly simplified refueling operations. More specifically, in the most simple form, on a second refueling operation of the client satellite, the refueling operation would begin at step <NUM> in.

Seventh, the use of a safety valve with quick connect nipple provides a means for refueling without requiring any rotary actuation above a threaded connection. This is a direct improvement over previous disclosures by eliminating the possibility of, for example, rotation of the whole safety valve body rather than just the actuation nut, such as could occur if the safety valve included a rotary actuation nut above its threaded connection to the FDV.

Eighth, the installation of the safety valve via threaded coupling nut occurs only after the refueling tool has been successfully registered and clamped onto the target FDV, unlike previously disclosed systems wherein the robotic arm with refueling tool and safety valve approach the FDV without registration. Additionally, the installation of the safety valve onto the FDV includes both visual and microswitch-based sensing, in conjunction with a compliant coupling nut, to ensure successful thread engagement.

Ninth, in relation to an overall refueling system and method, the comprehensive suite of tools provides a means and a method for which every step is robust and verifiable through visual and other sensor means. It is robust because the tools action can all be adjusted in real-time on-orbit to adapt to variation in worksite arrangement of feature tolerances. At each step of the refueling operation as the blankets, lock wire and FDV are manipulated, sensor information enables confirmation of a successful action or information necessary to take recovery actions.

Claim 1:
A suite of supporting tools (<NUM>) for preparing a client satellite to be refueled, comprising:
a suite of tools each having a specific function, each tool having a drive shaft (<NUM>) and tool section configured for its specific function;
a common tool base (<NUM>) to which each of said suite of tool tips (<NUM>) are permanently attached, said common tool base (<NUM>) including
a housing with a grasping interface on one side thereof configured for robotic grasping by an end effector (<NUM>) attached to a distal end of a robotic arm (<NUM>) mounted on a servicing satellite (<NUM>), the grasping interface including a grapple fixture, the other side of said housing configured to have a tool attached thereto and to receive said driveshaft of said tool;
two tool mechanism drive interfaces (<NUM>, <NUM>) used for enacting functions of a given tool tip via a drive actuator mechanism that is located in the (<NUM>, <NUM>) end effector of the robotic arm (<NUM>), one of said two tool mechanism drive interfaces being used to drive specific tool tip (<NUM>) on each of the support tools, and the second being use to drive a tie-down stowage mechanism for retaining the common base (<NUM>) when not grasped by the robotic arm,
a tool mechanism gear train (<NUM>) located in said housing that transfers rotation and torque from one of the tool mechanism drive input interfaces (<NUM>, <NUM>) to the tool driveshaft (<NUM>) via the tool mechanism gear train interface (<NUM>), for actuation of tool function.
a tie-down mechanism `active-half, coupled to, and driven by the second tool mechanism drive interface (<NUM>) for use when retaining said common base (<NUM>) in said tie-down mechanism when it is not being used and is demated from the end effector.