US20080075467A1

US20080075467A1 - Optical tracking system for airborne objects

Info

Publication number: US20080075467A1
Application number: US11/848,224
Authority: US
Inventors: Joseph Mickley; Raymond Stitt; Frank Saggio; Jane Pavlich; Gregory Wassick
Original assignee: Smiths Aerospace LLC
Current assignee: GE Aviation Systems LLC
Priority date: 2005-02-25
Filing date: 2007-08-30
Publication date: 2008-03-27
Also published as: AU2006216639A1; CA2599152A1; EP2289801A2; US7681839B2; IL210302A; EP2289801A3; US8104716B2; KR101329890B1; EP1851111A1; WO2006091779A1; AU2006216639B2; IL210301A0; IL210302A0; IL210301A; IL185475A0; US20060226293A1; CA2599152C; JP2008531377A; US20080067290A1; EP2289801B1

Abstract

An airborne object positioning system including a radiation emitter, a radiation receiver and a signal processor. Then the radiation emitter is adapted to direct radiation to a positioning area a defined distance from the radiation emitter, the radiation carrying a modulated location signal containing information corresponding to positions within the positioning area. The radiation receiver is adapted to receive at least a portion of the emitted radiation carrying the modulated signal and output a signal to the signal processor indicative of the modulation of the location signal of the received radiation. And the signal processor is adapted to process the outputted signal and identify a position within the positioning area indicative of the location in the positioning area of the received radiation.

Description

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This patent application is a Continuation In Part of U.S. patent application Ser. No. 11/249,262, entitled Optical Tracking System for Refueling, filed on Oct. 14, 2005, the contents of which are incorporated herein by reference in its entirety, which in turn claims priority to U.S. Provisional Patent Application Ser. No. 60/656,084, entitled Optical Tracking System for Refueling, filed on Feb. 25, 2005, the contents of which are incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

Aerial refueling is known. In an exemplary refueling scenario, a refueling drogue connected to a refueling hose is unreeled from a refueling aircraft (e.g., tanker aircraft) towards a receiver aircraft (an aircraft to be refueled), such as a fighter plane, a helicopter, etc. The receiver aircraft has a refueling probe extending from the aircraft. The receiver aircraft maneuvers to the refueling drogue and inserts its refueling probe into the refueling drogue, at which point the refueling drogue “locks” onto the refueling probe, and a transfer of fuel from the refueling aircraft to the receiver aircraft is conducted. In an alternative exemplary refueling scenario, a refueling boom is connected to the refueling aircraft, and the receiver aircraft is fitted with a refueling boom receptacle, and the receiver aircraft maneuvers to the refueling boom and/or the refueling boom is maneuvered to the receiver aircraft until the boom mates with the receptacle on the receiver aircraft.

SUMMARY OF THE INVENTION

In an exemplary embodiment of the present invention, there is an airborne object tracking system comprising, a radiation emitter, a radiation receiver and a signal processor, wherein the radiation emitter is adapted to direct radiation to a positioning area a defined distance from the radiation emitter, the radiation carrying a modulated location signal containing information corresponding to positions within the positioning area, wherein the radiation receiver is adapted to receive at least a portion of the emitted radiation carrying the modulated signal and output a signal to the signal processor indicative of the modulation of the location signal of the received radiation, and wherein the signal processor is adapted to process the outputted signal and identify a position within the positioning area indicative of the location in the positioning area of the received radiation.
In another embodiment of the invention, the radiation emitter is adapted to emit a focused optical beam and scan the focused optical beam over the positioning area.
In yet another embodiment of the invention, the emitted radiation is a focused optical beam, wherein the modulated location signal includes a plurality of digital data blocks, the plurality of digital data blocks containing information respectively corresponding to a plurality of discrete positions within the positioning area that respectively correspond to a current location of the focused beam within the positioning area.
In another embodiment of the invention, the radiation emitter is adapted to emit a focused optical beam and scan the focused optical beam over the positioning area.
In another embodiment of the invention, there is an airborne object tracking system comprising a radiation emitter, a radiation receiver, and a signal processor, wherein the radiation emitter is adapted to direct a beam of emitted radiation to an area away from the radiation emitter, the radiation including discernable properties that vary in a corresponding manner with varying orientation of the beam of radiation with respect to the radiation emitter, wherein the radiation receiver is adapted to receive at least a portion of the emitted radiation and output a signal to the signal processor indicative of one or more of the discernable properties of the received radiation; and wherein the processor is adapted to process the outputted signal and identify a first virtual orientation indicative of an orientation of the receiver relative to the radiation emitter when at least a portion of the radiation was received by the receiver.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of an aerial refueling operation according to the present invention.
FIG. 2 is a front view of an aerial refueling operation according to the present invention.
FIG. 3 is a side view of a drogue assembly according to the present invention.
FIG. 4 is a side view of a scanning operation according to the present invention.
FIG. 5 is a top view of a scanning operation according to the present invention.
FIG. 6 is a view of a focused optical elongated beam emitted by the radiation emitter.
FIG. 7 is a view of a focused optical elongated beam emitted by the radiation emitter impinging on a flat surface.
FIG. 8 is a view of a focused optical elongated beam emitted by the radiation emitter over an elapsed time.
FIG. 9 is a view of a focused optical elongated beam emitted by the radiation emitter impinging on a flat surface over an elapsed time.
FIG. 10 is a view of a focused optical elongated beam emitted by the radiation emitter.
FIG. 11 is a view of a focused optical elongated beam emitted by the radiation emitter impinging on a flat surface.
FIG. 12 is a view of a focused optical elongated beam emitted by the radiation emitter over an elapsed time.
FIG. 13 is a view of a focused optical elongated beam emitted by the radiation emitter impinging on a flat surface over an elapsed time.
FIG. 14 is a view of a virtual grid.
FIG. 15 is a view of a virtual grid superimposed over a scanning area.
FIGS. 16-17 present a schematic representing a two-pass scan over the virtual grid.
FIG. 18 depicts a location of the virtual grid with respect to the radiation emitter.
FIGS. 19-20 present a schematic representing a two-pass scan over the virtual grid, with the receiver positioned within the grid.
FIG. 21 presents a schematic of another type of scan utilized in the present invention.
FIG. 22 presents a symbolic representation of a digital data set utilized in an embodiment of the present invention.
FIG. 23 presents a schematic representing row orientation with respect to receiver aperture for a small beam/large aperture configuration.
FIGS. 24 and 25 schematically represent drogue positioning without the use of a virtual grid.
FIGS. 26 to 31 schematically represent various galvo designs.
FIGS. 32 to 33 b schematically represent beam emission in elapsed time.
FIGS. 34-40 schematically represent an emitter according to an embodiment of the present invention.
FIG. 41 is a side view of another aerial refueling operation according to the present invention.
FIG. 42 is a front view of the aerial refueling operation of FIG. 41.
FIG. 43 is a side view of receiver aircraft according to the present invention.
FIGS. 44-46 present an exemplary embodiment of an emitter in operation according to an embodiment of the present invention.
FIG. 47 presents an exemplary graph presenting sweep times (scan times) of a horizontal and vertical scan according to the present invention.
FIG. 48 presents an exemplary embodiment of a radiation receiver according to an embodiment of the present invention.
FIG. 49 presents an exemplary scenario where the number of scan lines received by the radiation receiver is utilized to determine slant distance from the radiation emitter to the radiation receiver.
FIG. 50 presents exemplary fields of view of a radiation emitter according to an embodiment of the present invention.
FIGS. 51-54 present exemplary performance characteristics of an exemplary tracking system according to an embodiment of the present invention.
FIG. 55 presents an exemplary scan grid that may be obtained utilizing an embodiment of the present invention.
FIG. 56 present exemplary performance characteristics of an exemplary tracking system according to an embodiment of the present invention.
FIG. 57 presents an high-level exemplary conceptual diagram of a system configured to address turbulence that may be used in the present invention.
FIG. 58 presents a schematic detailing overlapping fields of view of the radiation emitter.
FIG. 59 presents a schematic detailing an exemplary clock cycle of a radiation emitter according to an embodiment of the present invention and how those exemplary clock cycles may be used to determine whether the system is in calibration.
FIG. 60 presents a high-level exemplary conceptual diagram of a system configured for use with drogue tracking according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present inventors have determined that it is desirable that the location of an airborne object (e.g., a refueling drogue, a receiver aircraft in general, and a particular location on the receiver aircraft (e.g., the portion of the refueling probe that will interface with the refueling drogue/the receptacle in the receiver aircraft), etc.,) be identified relative to a refueling aircraft during aerial refueling operations. The present inventors have further determined that it is desirable that a system substantially maintain/adjust the position of a receiver aircraft, drogue, and/or refueling boom, or other airborne object (or plurality of airborne objects), relative to a refueling aircraft and receiver aircraft (or pertinent location thereon), respectively, so that mating of the receiver aircraft or other airborne object with the refueling aircraft can be better executed. Accordingly, an embodiment of the present invention is directed towards systems, methods and apparatuses for enabling determination of the position, relative to a fixed reference point on the refueling aircraft, of an airborne refueling device attached to the refueling aircraft, and/or determination of the position, relative to a fixed reference point on the refueling aircraft, of a receiver aircraft in general (or multiple receiver aircraft in general), and, in particular, of a certain location (or plurality of locations) on the receiver aircraft.
Moreover, some embodiments of the present invention are directed towards systems, methods and apparatuses for enabling a receiver aircraft in general and a boom/receptacle of a receiver aircraft in particular, to substantially maintain a position relative to the fixed reference point (also known as station keeping) based on this determined position. In an exemplary embodiment, this fixed reference point is a radiation emitter on the wing of the refueling aircraft, as will be discussed below. Further embodiments of the present invention are directed towards systems, methods and apparatuses for enabling a location of a refueling device (drogue, boom, etc.), relative to a receiver aircraft, to be determined. Some exemplary embodiments of the present invention, coupled with exemplary scenarios utilizing the present invention, will now be described followed by detailed discussions of particular embodiments of the present invention.
In a first embodiment of the present invention, as may be seen in FIGS. 1-3, there is a refueling drogue assembly 100 comprising a refueling drogue 105 connected to a distal portion of a refueling hose 110 (with respect to the attachment of the hose 110 to the aircraft 1000) that is in turn connected to an aircraft 1000. The aircraft 1000 includes a radiation emitter 200 that emits an optical beam in the general direction of the drogue assembly 105 (in particular, towards the receiver 300 on the drogue assembly 105, as will be discussed below). The beam is emitted in a scanning fashion such that the beam scans an area in relation to the radiation emitter in which the drogue 105 (receiver 300) is likely located, based on, for example, empirical data/analytical data for a given air speed, altitude, etc. This area is indicated by reference number 400 in FIGS. 1-3. The optical bean emitted by the radiation emitter 200 scans this area in a manner such that a discernable property of the optical beam changes as the orientation of the beam, with respect to the radiation emitter 200, changes. The discernable property of the optical beam that varies, in a controlled manner, with changing orientation of the beam with respect to the radiation emitter may be, for example, different discrete digital data blocks carried on the beam by way of beam modulation.
Accordingly, in an exemplary scenario utilizing the present invention, the optical beam scans over the scanning area 400 in a manner such that a discernable property of the optical beam changes as the beam is scanning over the scanning area. That is, the discernable property is different when the beam is located at one portion of the scanning area, as opposed to another portion of the scanning area, owing to the change in orientation of the beam with respect to the radiation emitter and the scanning area. This discernable property is carried on the optical beam and changes in a predetermined manner such that an analysis of this discernable property will enable the location of the beam, relative to the scanning area, to be determined. In this scenario, the radiation receiver 300 on the drogue assembly 100 is configured to output a signal to a signal processor 500 (after receiving/sensing the optical beam as it passes over the receiver) onboard the drogue assembly 100. This outputted signal from the receiver 300 is indicative of the discernable property carried on the optical beam that is received by the receiver. The signal processor 500 contains software and/or sufficient look up tables stored in a memory such that the signal processor 500, once it receives the signal from the receiver 300, may analyze the received signal and determine that the discernable property is indicative of a specific beam orientation with respect to the radiation emitter 200 and the scanning area 400. Because the geometry of the scanning area 400 relative to the radiation emitter is known, the location of the receiver 300 within the scanning area 400 may thus be determined by comparing the discernable property of the received radiation to information stored in a look-up table. Because the geometry of the refueling drogue assembly 100 relative to the receiver 300 is known, the position of the drogue assembly 100 relative to the radiation emitter may be determined.
As may be seen from FIGS. 1-3, the scanning area 400 is a square area in space that passes through the receiver 300 on the refueling drogue assembly 100. This area 400 is approximately normal to the direction of travel of the focused beam away from the radiation emitter (this is discussed in greater detail below).
In another embodiment of the present invention, as may be seen in FIGS. 41-43, there is a receiver aircraft 1105 including a receiver 300 trailing refueling aircraft (e.g., tanker) 1000. The refueling aircraft 1000 includes the radiation emitter 200 that emits an optical beam in the general direction of the receiver aircraft 1105 (in particular, towards the receiver 300 on the receiver aircraft 1105, as will be discussed below). As with the beam emission for the refueling drogue assembly application detailed above, a beam is emitted in a scanning fashion such that the beam scans an area in relation to the radiation emitter in which the receiver aircraft 1105 (receiver 300) is likely located, based on, for example, a given mission profile, real-time locational data, etc. This area is indicated by reference number 400 in FIGS. 1-3. As in the refueling drogue assembly scenario detailed above, the optical bean emitted by the radiation emitter 200 scans this area in a manner such that a discernable property of the optical beam changes as the orientation of the beam, with respect to the radiation emitter 200, changes.
An exemplary scenario utilizing the present invention parallels that detailed above with respect to the refueling drogue assembly, except that in this scenario, the radiation receiver 300 is located on the receiver aircraft 1105, which outputs a signal to a signal processor 500 (after receiving/sensing the optical beam as it passes over the receiver) onboard the receiver aircraft 1105 and/or onboard the refueling aircraft instead of the refueling drogue assembly 100. As with the refueling drogue scenario, this outputted signal from the receiver 300 is indicative of the discernable property carried on the optical beam that is received by the receiver 300 (except, of course, the receiver 300 is located on the receiver aircraft 1105 or other airborne object). Because the geometry of the scanning area 400 relative to the radiation emitter is known, the location of the receiver 300 within the scanning area 400 may thus be determined by comparing the discernable property of the received radiation to information stored in a look-up table. Because the geometry of the receiver aircraft 1105 relative to the receiver 300 is known, the position of the receiver aircraft 1105, in general, and a particular location on the receiver aircraft 1105 (e.g., the end of the refueling boom 1111), relative to the radiation emitter may be determined.

Scanning

The operational characteristics of the radiation emitter 200 shall now be described. FIG. 4 depicts a side view of an exemplary embodiment of the radiation emitter 200 and receiver 300 arrangement. FIG. 4 is taken from the perspective view depicted in FIG. 1. FIG. 4 shows that radiation emitter 200 emits a focused optical beam and moves that beam within lines 210 and 220. That is, from the side view of FIG. 4, radiation emitter 200 emits a beam in a scanning fashion such that the beam moves within the area bounded by lines 210 and 220 so that the scanning area 400 may be scanned. By way of example only and not by way of limitation, the radiation emitter 200 may emit a beam 202 at the orientation depicted in FIG. 4 at a time T₁, and then at a later time T₂, emit a beam 204 at a different orientation from that of beam 202. It is noted that in FIG. 4, the beam 202 is not intercepted by the receiver 300, whereas the beam 204 is intercepted by the receiver 300. FIG. 5 shows a top view of the radiation emitter 200 and the receiver 300 depicted in FIG. 4. From FIG. 5, it can be seen that the radiation emitter 200 emits beams within the area bounded by line 230 and line 240. Recognizing that FIG. 4 is a side view of the system and FIG. 5 is a top view of the system, a comparison of FIG. 4 with FIG. 5 shows that the volume (herein referred to as a scan zone and/or beam zone) bounded by lines 210 and 220 in FIG. 4 and lines 230 and 240 in FIG. 5 is in the shape of a cone, having its “top” located at the receiver 200. In the embodiment depicted in the Figs., the beam may be found within this volume/scan zone. In the embodiment depicted in FIGS. 4 and 5, the cone has a rectangular/square cross-section, as may be seen in FIG. 2. Thus the scanning area 400 will be rectangular/square shaped. (However, other embodiments of the present invention may utilize a circular cross-section or an oval shape cross-section. Indeed any shaped cross-section may be utilized as long as the goals of the present invention may be obtained.) It is noted that the exact geometry of this scanning area may not be perfectly square/rectangular in view of the fact that the distance from the receiver 200 to the scanning area changes with changing angular orientation of the beam with the radiation emitter 200. This phenomenon is discussed in greater detail below. However, for the present discussion, the scanning area will be treated as a rectangular/square shape that is approximately normal to direction of beam travel away from the radiation emitter 200. It is further noted that in many embodiments of the present invention, the beam will travel passed the scanning area 400, if the beam is not intercepted by the receiver 300. However, some embodiments of the present invention are such that the beam does not travel a significant distance beyond the receiver 300 so that the beam may not be easily detected beyond close proximity to the refueling aircraft 1000.
In a first embodiment of the invention, the radiation emitter 300 emits a focused optical beam that is a focused optical elongated beam 210 and scans the beam over the scanning area, as may be seen in FIG. 6. FIG. 7 shows the beam from the perspective of the scanning area, which is approximately normal to the direction of travel of the beam. That is, if the scanning area was a flat surface, and the beam 210 impinged upon the flat surface, the beam would look approximately like that shown in FIG. 7 when viewed in the direction of beam travel. In a first exemplary embodiment, the radiation emitter 300 first scans the focused optical elongated beam 210 over the scanning area starting from the top of the scanning area and ending at the bottom of the scanning area, in increments, as may be seen, for example, in FIG. 8. (Note that in other embodiments, the scanning may begin at the bottom and/or at the left or right sides (discussed below) and/or at any other location within the scanning area.) FIG. 8 shows, in a time-elapsed fashion, that at T₁, the beam 210 is at a first position. At T₂, the beam 210 is moved to a second position below T₁. At T₃, the beam 210 is moved to a third position below T₂. Again, the beam depicted in FIGS. 6-8 show the result of the focused optical beam as it would be if the beam impinges on the scanning area 400. FIG. 9 shows the focused optical beam impinging upon the scanning area over times T₁through T₁₃in a time-elapsed manner.
After scanning from the top of the scanning area to the bottom of the scanning area, the radiation emitter changes the orientation of the focused optical beam 210 from a horizontal orientation to a vertical orientation, as may be seen in FIG. 10. FIG. 11 shows the “impingement” of the beam 210 on the scanning area when the beam is elongated in the vertical direction. As may be seen in FIG. 12, radiation emitter 300 scans the beam 210 over the scanning area 400 starting from left to right, in increments. That is, at time T₁₄, the elongated beam impinges upon the scanning area in the left-most position. At T₁₅, the beam is moved from the left-most position to a position to the right. At T₁₆, the beam is again moved further to the right. FIG. 13 shows a time elapsed view of beam impingement over the scanning area from time T₁₄to time T₂₆.
Thus in comparing FIG. 13 with FIG. 9, it may be seen that the radiation emitter passes the beam over the scanning area in a two-pass or a dual-pass manner: first from top to bottom, and then from left to right (or from left to right, and then from top to bottom, etc.)

Positioning Coordinate System

According to a first embodiment of the present invention, at least a portion of the scanning area 400 includes a positioning area 450, as may be seen in FIGS. 14 and 15, in which the receiver 300 is likely to be located. In this embodiment of the invention, this positioning area 450 is entirely within the scanning area 400, as may be seen in FIG. 15, and thus the optical beam is scanned over the entire positioning area 450. However, in other embodiments, the boundaries of the positioning area 450 may exceed the scanning area 400.
The airborne object positioning system is adapted to virtually divide at least a portion of this positioning area 450 into a virtual grid 460. The virtual grid may include a plurality of distributed distinct sectors that spatially correspond to sub-areas within the positioning area. The sub-areas are dispersed within the positioning area in a geometrically defined manner. As may be seen in FIG. 15, receiver 300 of the airborne object (e.g., refueling drogue assembly/refueling boom/receiver aircraft, etc.), during normal operation of the airborne object positioning system, is typically located within this positioning area, and thus the receiver 300 will receive radiation from the radiation emitter, during normal operational conditions, as the radiation passes over the receiver. FIG. 16 shows a focused optical elongated beam in the horizontal position scanning over a row of distinct sectors/sub-areas within the virtual grid/positioning area 460/450. In a first embodiment of the present invention, the focused optical elongated beam scans from top to bottom in a continuous or in a step-wise manner, such that the focused optical elongated beam is scanned over each row of distinct sectors/sub-areas. After scanning over all of the rows, the focused optical elongated beam is then focused to be elongated in the vertical direction and is scanned over the positioning area, from column to column, again either in a step-wise or a continuous manner (see FIG. 17). As the optical beam moves from row to row and from column to column, the discernable property of the beam changes in a manner that may be detected by the receiver 300. That is, were the receiver to detect a discernable property of the horizontal beam while in, for example, the second row (that is, the discernable property corresponds to horizontal beam positioning within the second row), the radiation receiver will be able to detect a different discernable property were the beam and the receiver in the third row and so on. As noted above, the receiver is adapted to output a signal that is indicative of the discernable property of the received radiation, to convey information to the signal processor 500.
In an exemplary embodiment of the present invention, the grid 460 takes the form of that presented in FIG. 55. Here, each grid line number is encoded into each line by modulating the laser beam as detailed herein. In this exemplary embodiment, the resolution at 1803 feet is 1 inch of line spacing, and the grid generation rate is 20 Hz. It is noted that in some exemplary embodiments, the grid system operates in angular coordinates/spherical coordinates/radial coordinates, etc. In some such exemplary embodiments, line spacing is in units of angle, and the units of angle are converted to a linear distance through, for example, a radius, for human factors purposes (e.g., humans typically think in terms of Cartesian coordinates, as opposed to angular coordinates). By way of example and not by way of limitation, for high density line spacing, the system may convert between inches of resolution and delta angle of resolution. Such may be done, for example, by dividing the nominal radius in inches. For example, referring to FIG. 55, delta theta would equal 1 inch/21636 inches, which equals 0.00004621 rads. In some embodiments, the tangent and sine functions may be discounted because the angles are relatively small. Indeed, in some exemplary embodiments, the control system is such that there is no discernable difference because a control system utilizes an “error signal” algorithm, where the error signal is driven to zero, and where the liner, sine and tangent functions all pass through zero.

Airborne Object (Receiver) Positioning

As noted above, the distributed distinct sectors of the positioning area correspond to sub-areas within the positioning area, the sub-areas being disbursed within the positioning area in a geometrically defined manner. This geometrically defined manner corresponds to a known orientation of the sub-areas with the radiation emitter 200. Therefore, the orientation of the virtual grid 460 with respect to the radiation emitter is known. By way of example and not by limitation, FIG. 18 shows that the center of the grid 450 is located 100 feet behind and 10 feet below the receiver 300. (The center of the grid 450 is centered with the radiation emitter 300—i.e. the “X” value is 0.)
Because the orientation of the scanning area/virtual grid with respect to the radiation emitter 300 is known, the discernable property of the optical beam may be changed to correspond to the particular distinct sectors/sub-areas within the positioning area such that a unique discernable property may be carried on the optical beam for each distinct sector/sub-area. In this manner, the receiver 300, having received the radiation from the radiation emitter 200 outputs the signal to the signal processor 500 indicative of the distinct property carried on the optical beam received by the receiver 300, and thus, depending on the discernable property of the received radiation received by the receiver 300, by comparing the received discernable property to those in, for example, a memory, the signal processor 500 can determine which particular distinct sector/sub-area the receiver was located in when the receiver received the radiation.
The following is an exemplary scenario in which the airborne object 100/1105 determines its position utilizing the first embodiment of the invention. It is noted that by “determining its position,” it is meant that in some instances, component(s) onboard the airborne object determine the relative position of the airborne object to the receiver aircraft, in some instances a component(s) remote from the airborne object (e.g., on the receiver aircraft 1000) determines the relative position of the airborne object to the receiver aircraft, and in some instances both are the case. Indeed, some embodiments of the present invention are configured to simply transmit or otherwise convey information regarding the radiation received by the radiation receiver from the receiver/airborne object to which the receiver is attached, to the refueling aircraft, on which a processor 500 is located, so that the processor 500 may determine the relative location of the airborne object.
Referring to FIGS. 19 and 20, receiver 300 is located within row 2 and column 11 of the virtual grid 460. Radiation emitter 200 makes a first pass over the scanning area, and thus the positioning area, with the focused optical elongated beam, starting from the top of the scanning area and moving to the bottom of the scanning area, moving the beam from row to row. The discernable property of the beam is changed as the beam moves from row to row. When the beam passes over/through row 2, the receiver 300 detects radiation, and likewise detects the discernable property carried on the optical beam, the receiver 300 outputs a signal indicative of the discernable property of the received radiation to signal processor 500 which determine that the discernable property is indicative of beam location in row 2. The radiation emitter 200 continues to scan the beam over the scanning area. Once it reaches the bottom of the scanning area, the radiation emitter 200 then changes the orientation of the beam such that it is elongated in the vertical direction and scans the scanning area from left to right, moving the beam through each column in the virtual grid 460, changing the discernable property carried on the optical beam as the beam moves from column to column. When the beam passes over column 11, the radiation receiver receives radiation and outputs a signal indicative of the discernable property carried on that received radiation. The signal processor 500 receives the signal and analyzes the signal to determine that the discernable property is indicative of beam location in column 11. The signal processor 500, remembering that the prior signal was indicative of a beam position in row 2, recognizes that the receiver must be in column 11 and row 2 of virtual grid. (Note that in may embodiments of the present invention, the two-pass scan takes place relatively swiftly with respect to the dimensions of the virtual grid such that any movement of the airborne object/receiver during that time is negligible.) Because the virtual grid corresponds to sub-areas of the positioning area, by recognizing that the signal processor 500 received a signal indicative of beam location in the distinct sector of row 2 and the distinct sector of column 11, and that these sectors correspond to one another, the signal processor 500 may determine the location of the receiver within the positioning area, and thus determine the position of the receiver relative to the radiation emitter, because the position of the virtual grid relative to the radiation emitter is known.
FIG. 21 shows implementation of another embodiment of the present invention. Instead of utilizing a focused optical elongated beam in a two-pass/two-scan manner, this embodiment utilizes a traditional non-elongated optical beam, as shown, such that when the beam impinges on the scanning area, the beam forms a circle as opposed to an elongated line. In this embodiment, instead of scanning the beam in a two-pass manner over the scanning area, the radiation emitter 200 scans the beam in an X-Y raster over each of the individual discrete areas of the virtual grid 450. In this embodiment, the discernable property carried on the beam changes in a predetermined manner as the beam moves from each discrete area such that each discernable property is indicative of a specific discrete area within the virtual grid corresponding to a sub-area within the locating area. By way of example only and not by way of limitation, in reference to FIG. 21, the radiation emitter 200 scans the beam 280 across the virtual grid starting at block 1 (discrete sector 1), moving the beam from block 1 to block 2, then to block 3, etc., over to block 13, and then moves the beam to block 14, and then moves the beam to block 15, block 16, etc., repeating this pattern until the beam has scanned over all of the blocks. This scan is then automatically repeated. In the scenario depicted in FIG. 21, when the beam passes over box 24, the receiver 300 will receive the radiation, and thus the discernable property indicative of the beam when directed towards box 24, and then output a signal indicative of the discernable property of received radiation to the signal processor 500. The signal processor 500 then determines that the radiation receiver is located in box 24.
It is noted that in the above description of the X-Y raster, the beam was moved from box 13 at the upper right side of the grid, all the way on the left side of the grid. In another embodiment of the present invention, a raster scan may include, for example, moving the beam from box 13 to box 26, after which the beam is moved to box 25, box 24, etc., all the way to box 14, and then moved to box 27, and then to 28, and then to 29, etc., all the way to 39, and then moved to box 52, and then to 51, etc. Thus, the raster scan includes both the traditional scan performed by a cathode ray tube, as well as non traditional raster scans. Other scanning patterns may be used as well.
It is noted that in the above-described embodiments, the beam scans over the entire scanning area/virtual grid. Other embodiments of the present invention may be implemented where the beam only scans over a portion of the scanning area/virtual grid. By way of example only and not by way of limitation, such may be the case in a system where the signal processor 500 is in communication with the radiation emitter 200 such that after the processor 500 determines a general area within the grid in which the receiver 300 is located, the radiation emitter 200 may concentrate the beam on that general area, as opposed to over the entire area of the scanning area. That is, for example, if the signal processor 500 continues to determine that the receiver is in box 24, or is in the area of box 24, the radiation emitter 200 would not scan the area, say for example, around box 121. However, if the signal processor 500 did not receive a signal indicative of radiation within the area of box 24 for within a certain time period, the signal processor 500 may direct the radiation emitter 200 to again scan over the entire area so as to increase the likelihood that the receiver 300 will receive radiation. This may also be done in the case of the focused optical elongated beam method of scanning as well.

Airborne Object Position Control (Station-Keeping)

An embodiment of the present invention, utilizing the drogue positioning system detailed herein, to control the position of a refueling drogue, will now be described by way of an exemplary scenario. As a preliminary matter, it is noted that drogue control may be implemented according to the teachings of U.S. patent application Ser. No. 10/697,564 filed on Oct. 31, 2003, entitled Stabilization of a Drogue Body, the contents of which are incorporated herein in their entirety. U.S. patent application Ser. No. 10/697,564 claims priority to U.S. Provisional Application Ser. No. 60/498,641 filed on Aug. 29, 2003, the contents of which are also incorporated by reference herein in their entirety, the teachings of which may also be used to control the position of a refueling drogue. Further, it is noted that the drogue utilized in particular and/or drogue control in general may be implemented according to the teachings of Patent Cooperation Treaty Application PCT/US2006/049258 filed on Dec. 22, 2006, entitled Controllable Drogue, the contents of which are incorporated herein in their entirety. PCT Application Number PCT/US2006/049258 claims priority to U.S. Provisional Patent Application Ser. No. 60/752,380 to Mike Feldman, entitled Controllable Drogue, filed on Dec. 22, 2005, the contents of which are incorporated herein in their entirety.
Initially, the drogue 100 is extended from a drogue carrier attached to a wing of an aircraft 1000. The drogue assembly 100 will be extended a sufficient distance from the aircraft 1000 so that aerial refueling may be conducted. This distance, in an exemplary embodiment, is about 100 feet from the wing (and thus the radiation emitter), although in other embodiments, this distance may differ based on the local conditions and/or the type of mission required for the aerial refueling. The refueling drogue assembly 100 will be permitted to obtain a nominal position/effectively constant position (a constant position the location of which will vary with different atmospheric conditions, aircraft speed, etc.) with respect to the aircraft 1000, and thus the radiation emitter 200. At this time, according to this scenario, the aircraft to be refueled is a sufficient distance away from the refueling drogue assembly 100 such that the aircraft to be refueled does not impart any forces onto the drogue that may cause the drogue's position to move.
As noted above, wind gusts, turbulence, the receiver aircraft, etc., may impart forces on the drogue assembly 100 that will make the drogue move from its “effectively constant position.” Based on empirical and/or analytical analysis, it is known that, for example, under the given set of circumstances for a particular refueling mission, the position of the drogue/receiver may be maintained within about a 6 inch radius of a nominal location, in some embodiments, within about 2-3 inches, and in others even smaller, such as about 1-2 inches and/or even less than an inch. In some embodiments, the system accounts for turbulence in the frequency range of 1-3 Hz that can cause a few feet of drogue displacement. Moreover, in some embodiments of the invention, the stabilization system may account for bow wave (from the receiving aircraft), which induces translation. Specifically, the system may account for bow wave of steady state that can cause about five feet of displacement and/or 2 to three feet of displacement, depending on such variables as, for example, the control surface size, control surface deflection, control surface actuator force, etc, of the drogue active control system. Some embodiments of the present invention may be implemented to account for forces that cause the drogue to move as much as 10 feet in any direction from a “nominal position” relative to the radiation emitter 200. (For other missions, the drogue could move more or less.) Accordingly, for this particular mission, the area of likely movement of the drogue, i.e., this “10 feet in any direction,” will define the scanning area 400 in a first embodiment. That is, the geometry of the scanning area 400 will be set to be 20 feet by 20 feet, centered about the nominal position of the drogue, such that the receiver 300 is very likely to be located within that area during a normal refueling operation. (For other missions, the area may be 10 feet by 10 feet, 10 feet by 20 feet, or more or less, depending on the conditions of the mission. If refueling is being conducted during relatively calm atmospheric conditions, the scanning area would likely be smaller than a scanning area for un-calm conditions.)
It is noted that the location of the scanning area 400 may be adjusted based on the nominal location of the drogue assembly. That is, for example, referring to FIG. 1, for a first type of refueling mission, the nominal location of the drogue may be located, on average, 105 feet in the Z direction, and minus 5 feet in the Y direction, from the radiation emitter 200. In a second type of refueling mission, the drogue may instead nominally be 90 feet from the radiation emitter 200 in the Z direction, and be negative 15 feet in the Y direction from radiation emitter 200.
It is noted that in some embodiments of the invention, the drogue positioning system is configured to adjust the location of the scanning area to conform to the location of the receiver 300. By way of example, the radiation emitter 200 may move the scanning area over a wide area to initially find the nominal location of the drogue, and then refine the scanning area about the drogue. It is noted that in other embodiments of the invention, the drogue positioning system may instead simply start off with a very large scanning area such that the beam may be more dispersed, such as in the instance of use of a focused optical elongated beam, thus covering a greater area. Upon identification of the nominal location of the drogue/receiver, the scanning area may be narrowed accordingly.
In other embodiments of the present invention, the refueling aircraft may include a device that detects the nominal location of the drogue, and uses this detection to direct the scanning area. In other embodiments of the invention, an operator on-board the aircraft 1000 directs the scanning area at the drogue.
It is also noted that in some embodiments of the present invention, it is not necessary that the scanning area be centered on the nominal location of the refueling drogue. Such may be the case in conditions such that it is expected that the drogue will move from the nominal location in some directions more than in other directions.
Once the drogue is nominally located, and the scanning area is directed to this location, the positioning system may begin operating to identify the position of the drogue within the scanning area. Assuming a virtual grid having 13 columns and 13 rows, as is exemplarily depicted in FIG. 14, if the nominal position of the refueling drogue is known, the scanning area/grid will be positioned such that column 7 and row 7 are positioned at the nominal location of the refueling drogue. As discussed above, the radiation emitter 200 may scan over the scanning area, and thus over the virtual grid. The signal processor 500 will determine where the receiver/drogue assembly is located within the grid based on the radiation received by the receiver 300 while the radiation emitter 200 scans the scanning area. In this exemplary scenario, if the signal processor 500 determines that the drogue/receiver 300 is still located at virtual row 7, column 7, the active control system of the drogue assembly will not change its position. However, if, for example, the signal processor 500 determines that the drogue has moved within the virtual grid to row 6, column 7, the signal processor 500 will output a signal to the active control system to move the drogue downward (i.e., in the negative Y direction). The active control system may be commanded to move the drogue downward until the receiver again receives radiation from the signal processor that the drogue/receiver is again located at its nominal position. If, for example, the radiation is indicative of receiver position in row 7, column 7, the signal processor will tell the active control system to stop directing the drogue downward. However, if for example the signal processor determines that the drogue is now at row 8, column 7, this signal processor will output a signal to the active control system to direct the drogue upwards, (i.e., in the positive Y direction). Thus, the drogue positioning system may be utilized in an iterative manner to control drogue location. It is noted that other embodiments of the present invention may operate in different manner. That is, for example, if there is a repeating tendency for the drogue to move from row 7, column 7 to, for example, row 6, column 7, the active control system may adjust a trim on some of the control surfaces of the drogue assembly to direct the drogue back to row 7, column 7, such that this tendency is negated. Basically, the drogue positioning system may be used in any manner that will enable the position of the drogue to be determined such that the position may be adjusted/controlled utilizing an active control system.
It is noted that in some embodiments of the present invention, the distal portion of the refueling hose will be the portion of the drogue assembly that is actively controlled. This is because in some embodiments, the drogue assembly 100 may include a flexible joint, which may be located between the hose 110 and the drogue 105, allowing the drogue 105 to pivot about the centerline of the hose (see, FIG. 3). In such embodiments, it is typically the position of the distal end of the hose that is controlled. In other embodiments, typically, where the hose is rigidly connected to the drogue 105, it is the position of the drogue 105 that is controlled. Accordingly, in some embodiments of the invention, the receiver is rigidly connected either directly to or by way of a rigid interface to the controlled component. If the position of the hose is to be controlled, the receiver will typically be rigidly connected to the hose, as may be seen, for example, by FIG. 3. It is noted that some embodiments of the present invention extend to a retrofit kit including an adapter on which a receiver is mounted that couples a drogue 105 to a hose 110. Depending on which component is to be controlled, the adapter is rigidly connected to that component. In sum, by reference to controlling the location of a refueling drogue assembly, it is meant that at least one point on/in the refueling drogue assembly (drogue, distal portion of the hose, adapter, etc.) is controlled, recognizing that other parts of the drogue assembly may not be controlled.
It is noted that while the just-described scenario is detailed in terms of controlling the position of a refueling drogue, the scenario is readily applicable to controlling the position of a host of other airborne objects, such as, for example, a refueling boom, a receiver aircraft (or a plurality of receiver aircraft), including autonomous drones, etc. Accordingly, embodiments of the present invention include any device, system, method and/or algorithm which permits some or all of the above-discussed actions to be undertaken with a variety of airborne objects including receiver aircraft, etc.
Embodiments of the present invention may be practiced in accordance with the teachings herein to enhance aerial refueling by directing one or both of an aerial refueling device and a receiver aircraft, based on the relative positioning information obtainable according to the teachings herein, to mate with one another. That is, the relative positioning information obtainable according to the teachings herein may be used to “fly” (in some embodiments, automatically) a refueling drogue (or refueling boom) to a receiver aircraft, fly a receiver aircraft to a refueling drogue, and/or do both, automatically. Accordingly, embodiments of the present invention include devices, systems, methods and algorithms for use in mating (in some embodiments, automatic mating) of one airborne object with another airborne object.

Specific Features of Some Embodiments

Specific features of the airborne object positioning system will now be discussed.
As noted above, the radiation emitter 200 may output a focus optical beam. It will be noted that other embodiments of the present invention may utilize other types of radiation. Basically, any type of radiation that may be utilized to determine the airborne object location according to the present invention may be used. By way of example only and not by way of limitation, electromagnetic radiation may be utilized. Such an embodiment may utilize technologies associated with VOR and ILS. As noted above, the radiation emitter emits radiation that carries a discernable property that may be received by a receiver and analyzed. This discernable property is used as a reference by the signal processor 200 to determine the location of the receiver/airborne object within the virtual grid and the positioning area. This discernable property, in some exemplary embodiments, is created by modulating the beam with digital data blocks that represent the current location of the beam in the scanned area/positioning area. An example of a digital data block may be seen in FIG. 22. FIG. 22 shows a schematic drawing of a modulation of a projected beam. In FIG. 22, a block is exploded. By way of example, only, this block represents a 20-bit data block typical of the other blocks. In this block, the first 8 bits are header information, while the remaining 12 bits represents information regarding the row or column at which the focused beam is directed. FIG. 22 shows that the block is 0.25 inches in length. This corresponds to the width or height of a column or row, respectively, at the tracking area. That is, as the beam scans over the area, the beam is modulated such that modulation sufficient to indicate a column or row is completed as the beam moves 0.25 inches in the area. For example, the first 0.1 inch of movement corresponds to header information, while the last 0.15 inches of movement corresponds to the row/column information. Thus, in this embodiment, the modulation is substantially continuous. (Although in other embodiments, the modulation need not be continuous.) Because in some embodiments the processor 500 is configured to recognize a header, the processor may thus determine that the received radiation is indicative of a new row or column once a new header is received. It is noted that in other embodiments of the present invention, a 24 bit word data block is utilized, where 20 bits are used for positioning, and the spare bits may be used for other informational purposes such as, for example, data link of commanded positions, etc. The approximate data bit rate in an exemplary embodiment is 26 Mhz.
In some embodiments of the present invention, modulation is obtained by cycling the intensity of the beam, which in some embodiments corresponds to shutting the beam off (or otherwise blocking the beam) and then turning the beam on (or otherwise directing the beam to the area). Other embodiments may utilize multiple intensities. Embodiments of the present invention may utilize standard digital modulation techniques, such as those utilized in encryption, if those modulation techniques may be coupled to beam location/direction.
It is also noted that the discernable property of the beam may be unique to a given column and row. That is, every column and every row, collectively, may have different discernable properties associated with that column/row. For example, column 2 will be associated with a discernable property that is distinct with all the other discernable properties for all other columns and rows. Such may be accomplished, for example, by utilizing a “smart header:” a header that includes information pertaining to whether the beam is aligned horizontally or vertically, but still allows for the processor to determine that a new block is being transmitted (discussed more below). However, other embodiments of the present invention may utilize the same discernable properties between columns and rows. For example, column 1 may be correlated to a discernable property that is the same as that for row 1, row 2, or row 3, etc. However, in such a situation, based only on the discernable property, without more, the system would not know whether the discernable property is indicative of a column position or a row position. In such instances, for example, the timing between the first and the second pass of the two-pass scan may be adjusted such that every first receipt of radiation is a scan from top to bottom (e.g., a scan indicating row position), and every second receipt of radiation is a scan from left to right (e.g., a scan indicating column position), or in any other pre-determined pattern. Such may be determined, by way of example, by pausing in-between each scan for a certain amount of time. For example, a scan from top to bottom might be separated by a predetermined time period from the following scan from left to right. The scan from left to right may in turn be separated by different predetermined time period. The signal processor 500 may be programmed to look for different time periods between receipt of outputted signals from the receiver and, from a look-up table, recognize the type of scan. Alternatively, the beam may carry two or more discernable properties at the same time. For example, one property may be indicative of the type of scan (either top/down or left/right) and the other may be indicative of the location within the scan area, i.e., what column/row).
By way of additional example, in the case of utilizing a non-elongated (normal beam) such is shown in FIG. 21, one discernable property may be adjusted to indicate the beam's location within a column, while the other discernable property may be adjusted to indicate the beam's location within a row such may be used for two-pass scans as well. In summary, any type of modulation/change in discernable property of radiation that may be utilized to correlate beam location within the virtual grid with respect to the radiation emitter may be utilized to practice the present invention.
It is noted that beam receiver overlap may be utilized to practice the present invention. That is, by way of example, some embodiments of the present invention may utilize a ratio of 6 to 1 for beam/receiver overlap, although other embodiments may utilize a larger or smaller ratio. Overlap may be obtained by utilizing either a big beam/small receiver, or a small beam/big receiver. FIG. 23 shows an exemplary scenario utilizing an embodiment utilizing a big receiver/small beam. In FIG. 23, the rows (and although not shown, the columns) of the virtual grid are such that multiple rows (and columns) fit within the receiver aperture when virtually overlaid with the receiver aperture. In the embodiment shown in FIG. 23, 7 rows fully fit within the receiver aperture, although again, more or less rows may be utilized in other embodiments. In an embodiment according to FIG. 23, the discernable property may change at least seven times as the beam moves through each of the rows, and thus the receiver may output seven signals, each of which indicate a specific discernable signal. This will be, of course, the case for the columns of the grid as well, providing that the columns are dimensioned similar to the rows of the grid. In this regard, column size and row size may be directly correlated to the ability to control the beam and to vary the discernable property of the beam.
In a first embodiment of the present invention, it is expected that the columns and rows of the virtual grid will be 0.25 inches in height/width when the scan area is about 100 feet from the radiation emitter and about 10 feet below the radiation emitter. Thus, the discernable property of the beam may change as the beam moves 0.25 inches in the sweeping direction. Of course, other embodiments of the present invention may use a larger or smaller row/column height/width. By way of example, some embodiments may utilize heights/widths of 0.1 inches or less and/or 1.0 inches or more. In many embodiments of the present invention, the discernable property of the beam will change as it moves from one column to the other. Thus, the discernable property may change less frequently for grids utilizing rows and columns that are larger. According to some embodiments of the invention, the scan area will be a 120 inch×120 inch square, at 100 feet from the radiation receiver, and the row/column height/width will be 0.25 inches. Thus, the scan area will be made up of 480×480 columns and rows (scan lines). However, it will be noted that other embodiments of the present invention may use different sized/shaped scan areas. By way of example only, and not by way of limitation, a circular scan area may be used where the beam is scanned in a helical pattern, starting from the center and moving outward. In such an embodiment, again, it may be possible to have an interactive system such that the scan begins at the center, where receiver is most likely to be located, and then scans outward, and once the radiation receiver receives the radiation, the radiation emitter may be controlled to reset the scan again, starting at the center and/or at the approximate location of the airborne object. Other embodiments may utilize a rectangular section or any other shaped section that will achieve the results of airborne object positioning, according to the present invention.
In the example of FIG. 23, where the height of each row represents 0.25 inches, the receiver will receive fully seven different discernable properties carried on the received radiation, and output seven different signals to the radiation receiver, (or alternatively, output a single signal carrying a data package which is indicative of the seven indicative properties received by the received radiation). In other embodiments, the receiver simply outputs signals indicative of all information received, and lets the signal processor 500 determine whether a full data set has been received. The signal processor 500 will analyze the signal(s) and determine that radiation has been received that is indicative of seven different rows within the grid, and thus the exact position within the virtual grid may not necessarily be known. In some embodiments, the receiver and/or signal processor determine whether a full data set has been received base on the number of bits received between receipt of headers. For example, in the scenario depicted in FIG. 23, the receiver will not receive a header until row 2, and thus will know to ignore the information preceding. Also, after receiving the header of row 9, the receiver will not receive another header, and also will not receive a full 20 bits of information before the radiation stops, and thus will know to ignore any information following the last receipt of 20 bits. In such a scenario, the receiver and/or signal process such that the seven different rows are averaged in a manner such that the average row location would be determined. For example, in the figure of FIG. 23, the average row will be row 5. If, for example, the receiver aperture was moved downward 1 row such that the average row was row 6, the signal processor could output a signal to the active controller to adjust the control to move the airborne object upward, such that the average of the received rows would again be row 5. Still further, referring to FIG. 23, it may be seen that radiation from row 1 and radiation from row 9 would also be received by the receiver, if only in a fractional amount. According to an embodiment of the invention, this partial received radiation may correspond to only a receipt of a partial data set, and the receiver may be of a design such that the receiver will not output a signal upon receipt of only a partial data set/partial amount of radiation. That is, with reference to FIG. 23, the receiver would only out put seven signals, not nine signals (i.e., the receiver would basically ignore the radiation of column 1 and column 9. However, other embodiments of the present invention may output a signal upon even receipt of a partial data set.
In another embodiment of the invention, the number of bits received during a pass is used to obtain a hyper accurate position within a sector/sub-area. Referring to FIG. 23, the processor 500 know the number of bits that it received, and know that it received a full data set for lines 2 through lines 8. For example, the processor 500 will know that it received 7×20 bits for rows 2 through 8, that it received, for example, 5 bits before it received a full 20 bits representing row 2, and that it received 10 bits after it received a full 20 bits representing row 8. The processor can thus determine that the center of the receiver is located closer to row 9 than row 1. In fact, the processor can determine that the center of the receiver is about 12.5 bits away from the top of row 5 (e.g., 155 bits received, divided by 2, minus the 5 bits received from line 1=72.5 bits below the top of line 2, and if each line represents 20 bits, the center will be 12.5 bits away from the top of row 5—the distance from the bottom of row 5 may be determined as well, both to verify the correctness of the calculation, or to smooth possible rounding errors.) Thus, instead of simply being able to determine that the receiver is centered within row 5, a determination may be made that the receiver is centered 0.15625 inches below the top of row 5 (12.5 bits divided by 20 bits times 0.25 inches). Other algebraic manipulations may be utilized as well to practice this embodiment of the invention to obtain hyper accurate results.
A processing algorithm that may be used in the present invention is as follows. Assuming that the raster is numbered top down and that the message packets are numbered left to right, the center raster scan line is:

- A. Lowest_number_scan_line_detected+((Highest_number_scan_line_detected−Lowest_number_scan_line_detected)/2).
- B. The center packet is: For the scan line from “A,” above, lowest_packet number+((highest_packet_number−lowest_packet_number)/2).

As noted above, embodiments of the present invention may either utilize big beam/small receiver or a small beam/big receiver. Any size beam and any size receiver may be utilized providing that airborne object positioning may be obtained according to the present invention.
Many of the embodiments, according to the present invention utilize the virtual grid as detailed above. However, other embodiments of the present invention may be practiced without utilizing a virtual grid. By way of example, a focused optical non-elongated beam, such as that according to FIG. 21, may be scanned such that the beam contains discernable properties that are indicative of the angular orientation of the beam with respect to the radiation emitter. In such a situation, two reference planes may be created, which may be, but do not necessarily have to be orthogonal to one another. For example, FIGS. 24 and 25 show angular orientation from planes extending out of the view passing through the nominal angle of beam direction as may be seen. According to FIG. 24, the receiver is located at plus 10 degrees above the plane passing through the nominal angle. According to FIG. 25, the receiver is located at plus 5 degrees to the side of the plane passing through the nominal angle. If the nominal “location” of the beam is plus 10 degrees and 0 degrees, the active control system may be directed to steer the airborne object back 5 degrees. In such an embodiment, both the elongated beam and the non-elongated beam method of scanning may be used. If the non-elongated beam method is used, the beam zone, the beam zone may include a plurality of distributed distinct vector of known orientation with the radiation emitter such that if the signal processor determines which distinct vector a received beam coincides with, the orientation of the receiver relative to the radiation emitter may thus be determined. That is, the distinct vectors correspond to actual orientations of the beam with respect to the radiation emitter, the actual orientations being disbursed within the beam zone in a geometrically defined manner.
In such an embodiment, the radiation emitter is adapted to direct a beam of emitted radiation to an area away from the radiation emitter, the radiation including discernable properties that vary in a corresponding manner with varying orientation of the beam of radiation with respect to the radiation emitter. By way of example, the radiation emitter is adapted to emit a focused optical beam modulated with digital data blocks, the modulated digital data blocks respectively indicative of discrete orientations respectively corresponding to orientations of the beam relative to the radiation emitter. Some of the varied discernable properties are respectively indicative of discrete orientations respectively corresponding to orientations of the beam relative to the radiation emitter in a first reference frame, and wherein at least some of the varied discernable properties are respectively indicative of discrete orientations respectively corresponding to orientations of the beam relative to the radiation emitter in a second reference frame.
Based on the output of the receiver, the processor is adapted to process the outputted signal and identify a first virtual orientation indicative of an orientation of the receiver relative to the radiation emitter when at least a portion of the radiation was received by the receiver. By way of example, the signal processor is adapted to analyze a first outputted signal from the receiver that is indicative of a first discernable property of the received radiation indicative of a first discrete orientation corresponding to a first orientation of the beam relative to the radiation emitter in the first reference frame at the time that the radiation was received. Still further by way of example, the signal processor is adapted to analyze a second outputted signal from the receiver, the second outputted signal being indicative of a second discernable property of the received radiation indicative of a second discrete orientation corresponding to a second orientation of the beam relative to the radiation emitter in the second reference frame at the time that the radiation was received. Accordingly, the signal processor is adapted to identify a virtual location of the receiver relative to the radiation emitter based on the analysis of the first and second outputted signals.
As discussed above, some embodiments of the present invention are configured to permit the airborne object 100/1105 to maintain a position relative to the radiation emitter. Such maintenance may be performed in some embodiments without the need for communication between the radiation emitter and the airborne object 100/1105. For example, the signal processor 500 on the airborne object 100/1105 may be furnished with look-up tables sufficient to analyze the signals from the receiver and identify the current location of the refueling drogue within the positioning area/virtual grid. However, in other embodiments, the airborne object may be in communication with the refueling aircraft 1000, or other location remote from the airborne object. In such embodiments, a simple communications link may be established from the receiver 300 and/or the processor 500 to components onboard the aircraft 1000. Indeed, in some embodiments, position determination is determined at a location remote from the airborne object, the airborne object merely communicating information about the received radiation sufficient for the remote location to evaluate the relative position of the airborne object.
FIG. 60 presents a high level exemplary control algorithm usable in the target (e.g., a refueling drogue) for evaluating position of the target with in the grid(s).
An embodiment of the prevent invention include kits that comprise devices that will enable conventional refueling drogue or other airborne object to be retrofitted for positioning determination and/or to be actively controlled. (Such embodiments also extend to methods of conversion as well.) Such devices might come in the form of a pack that includes a receiver, a signal processor, and/or control surfaces, sensors, etc., necessary to implement positioning determination and/or active control. In some embodiments of the present invention, a pack may have the positioning system and the active control system in one pack, or at least the components that physically interface with the air stream (e.g., the vanes, the control surfaces, etc.) required to implement those systems (the other components may be added directly to the refueling aircraft as long as there is a means to interface with the retrofit packs). Thus, any kit/pack that contains any or all of the above elements of the airborne object positioning system and/or the active control system and/or will permit the implementation of the functions of position determination and/or active control on an existing refueling drogue or other airborne object, may be utilized to practice some embodiments of the invention
It is further noted that the present invention includes software, firmware and/or computers (including simple logic and/or error circuits) adapted to implement the above techniques. Also, while some embodiments of the present invention may be practiced manually, other embodiments may be practiced automatically. Thus, the present invention includes any device or system that may be configured or otherwise used to implement the present invention in an automated manner.
Some embodiments of the present invention may be configured to generate electricity at the refueling drogue 100, to power the receiver, the signal processor and/or the active control system, etc.
As discussed above, the scanning area is treated as being an area that is flat. However, under such treatment, the distance of the scanning area to the radiation emitter will be larger at the edges of the scanning area than at the center of the scanning area (assuming a scanning area centered about the nominal direction of the emitted beam), owing to the change in angle of the beam between the center and the edges of the area. Thus, the distinct sectors of the virtual grid/sub-areas may differ in size between those at the center of the grid/locating area and those at the edges to account for this phenomenon. Indeed, in some embodiments of the invention, the grids are defined by the optical beam. That is, how the beam changes controls the size and shape of the virtual grid/the sub areas. In this respect, the grid is more of a convenient way to express location of the airborne object. If the present invention is practiced to maintain a position of the airborne object, uniformity of the virtual grid is not needed. In fact, the grid could be dispensed with entirely, providing that logic is utilized to control the position of the airborne object. (For example, large look-up tables may be utilized and/or modified fly-by-wire logic may be used corresponding to the various discernable properties as they correspond to orientation of the beam with the radiation emitter. For example, exhaustive if-then routines might be utilized.) Alternatively, the angular change of the orientation of the emitted beam may be varied to utilize a consistently sized grid (i.e., larger angular changes while scanning at the edges of the grid/tracking area than while scanning near the center of the grid. Also, a combination of the two may be utilized.
In this regard, the tracking area/virtual grid may be treated as a curved surface instead of a flat area. In this regard, it is noted that when the airborne object 100/1105 moves relative to the radiation emitter, it is likely that the airborne object 100/1105 will move in three dimensions. That is, assuming that the refueling hose 110 is of a constant length during refueling, a change in position in the “X” or “Y” direction (referring to FIGS. 1 and 2) will result in a change in position in the “Z” direction. Thus, embodiments of the present invention may be implemented that account for the position of the airborne object in three dimensions (i.e., a positioning volume may be utilized to determine the position of the airborne object). Such may be accomplished by adding, for example, a second radiation emitter or a second radiation receiver a know distance from the first radiation emitter or the first radiation receiver, respectively, and triangulating between the two. Alternatively or in addition to this, some embodiments of the present invention might utilize two or more receivers spaced about the airborne object that analyze which beam was received by which receiver during a given pass. For example, if at a distance of 100 feet from the radiation emitter, for a given location within the receiving area, receiver A is expected to receive radiation carrying a property indicative of receiver position at column 45 and receiver B is expected to receive radiation carrying a property indicative of receiver position at column 57, and if at a distance of 102 feet from the radiation emitter, again for the “same” location within the receiving area receiver A is expected to receive radiation carrying a property indicative of receiver position at column 44 and receiver B is expected to receive radiation carrying a property indicative of receiver position at column 58, the distance in the “Z” location may be obtained based on this phenomenon, as applicable.
As just detailed, embodiments of the present invention may utilize two or more radiation emitters 200. In such a scenario, when utilizing radiation emitters that have the same field of view (discussed in greater detail below), the total scanned area may be increased by a factor of 2 or more. For example, if a first radiation emitter has a field of view of 45 degrees, and the second radiation emitter has a field of view of 45 degrees, a combined field of view of 90 degrees may be obtained (three such emitters might yield 135 degrees, etc.). In some embodiments, the fields of view may be interleaved such that the two radiation emitters overlap a single scan area. (See FIG. 58 for an exemplary scenario of two radiation emitters with a 45 degree field of view overlapping each other.) In embodiments of the present invention where respective scan areas of radiation emitters overlap one another, redundancy is achieved in the overlap area (depending on the extent of the overlap, a larger field of view may be achieved as well, as is depicted in FIG. 58.) Further, data may be obtained from the overlap for use in fault detection routines. Also, overlap may be set up to be weighted in the “X” direction, the “Y” direction, or may be weighted symmetrically with respect to both directions. Some embodiments of the present invention are configured to vary the fields of view/the directions of the fields of view of the radiation emitters during operation. That is, some embodiments of the present invention are configured to “steer” the fields of view towards areas of interest with respect to the aircraft 1000. Any device, method, algorithm and/or control system that will permit scan areas to overlap may be utilized to practice some embodiments of the present invention.
Also as just detailed, embodiments of the present invention may utilize two or more receivers 300. This may be done, for example, in a scenario where roll attitude determination of a target (e.g., the drogue, the receiver aircraft, etc.) is desired. In other embodiments, the multiple receivers may be arrayed on respective multiple targets/airborne objects. By way of example, a plurality of receivers may be arrayed on a plurality of receiver aircraft 1105, respectively, and the plurality of receiver aircraft may be tracked. That is, in this exemplary embodiment, multiple receiver aircraft may be optically tracked by a single aircraft 1000 and/or tracked at a location remote from the aircraft 1000 and the multiple receiver aircraft. In such embodiments, one or more emitters 200 may be utilized (e.g., as detailed herein, multiple emitters 200 may be utilized to expand the scanned area), although in some embodiments, a single emitter 200 may be utilized providing that it provides a large enough field of view for the multiple targets to be in the field of view (e.g., sufficient room for maneuvering, etc.). It is noted that in some embodiments of the present invention, a first target may be relatively close to the emitter 200 (such as, for example, during the final approach towards a refueling drogue/boom, while a second target may be relatively far from the emitter 200, thus providing sufficient “room’ for the two targets to maneuver).
Accordingly, in an exemplary scenario utilizing the present invention, two or more airborne objects are positioned proximate the refueling aircraft, each having at least one radiation receiver, respectively. The receivers respectively receive the laser beam(s) emitted from one or more radiation emitters onboard the refueling aircraft 1000, and the modulation of signal(s) carried on the received laser beam(s) is analyzed to determine respective positions of the receivers (and thus the position of the respective airborne objects). Accordingly, the relative position of a plurality of airborne objects may be determined simultaneously. It is again noted that as with a single airborne object, the receiver aircraft (or other remote location from the airborne objects) may be configured to receive information indicative of the location of the airborne objects (e.g., true positioning coordinates, information pertaining to the radiation received by the respective receivers onboard the airborne objects, etc.) transmitted to the receiver aircraft (or other location remote from the airborne objects). Such a scenario will likely be practiced in the event that the airborne objects are drones.
In yet other embodiments, especially those relating to determining the relative location of a receiver aircraft/a component on the receiver aircraft, the “Z” location of the receiver 300 may be determined by configuring the receiver 300 with an aperture of known size so that range information may be extracted based on the number of scan lines that pass through the aperture during a Y sweep and/or an X sweep and/or both. In this regard, referring to FIG. 49, where each scan line represents a single cycle of the “data clock” that is imposed on the laser beam, for a constant aperture size, it may be seen that there will be more scan lines (and therefore more clock cycles) within the field of view of the aperture as the aperture moves closer to the radiation emitter 200 (note the number of lines that pass through the aperture at “Range_B” as compared to “Range_A,” the latter being more distant from the emitter 200 than the former). In some embodiments, the number of lines (or clock cycles, as is detailed herein) that pass through the aperture to be received by a detector in the receiver 300 is nonlinearly proportional to the distance from which the receiver 300 is located from the radiation emitter 200. Accordingly, an exemplary embodiment of the present invention includes a system adapted to extract information from the radiation emitted from the radiation emitter which is received by the radiation receiver indicative of a straight-line distance between the radiation emitter and the radiation receiver. In an exemplary embodiment, the extracted information is based on the amount of radiation received by the radiation receiver during a predetermined period of time, and the system includes an algorithm having the parameters such that the more radiation that is received by the radiation emitter during the predetermined period of time, the smaller the straight-line distance between the radiation emitter and the radiation receiver. In some embodiments, the system is configured such that the radiation emitter modulates an intensity of the beam according to a periodic cycle. The system is configured to extract information from the radiation emitted from the radiation emitter which is received by the radiation receiver indicative of a straight-line distance between the radiation emitter and the radiation receiver. This information may be based on the number of modulations detected by the radiation receiver during a predetermined period of time. The system may include an algorithm having the parameters such that the greater the collective intensity of radiation that is received by the radiation emitter during the predetermined period of time, the smaller the straight-line distance between the radiation emitter and the radiation receiver.
In yet other embodiments, the radiation emitter cycles emission of the beam (i.e., turns the beam on and off) according to a periodic cycle to direct a plurality of lines towards the radiation receiver. The system is adapted to extract information from the radiation emitted from the radiation emitter which is received by the radiation receiver indicative of a straight-line distance between the radiation emitter and the radiation receiver—the information being based on the number of emission cycles detected by the radiation receiver during a predetermined period of time. Also, the system includes an algorithm having parameters such that the higher number of emission cycles that are received by the radiation emitter during the predetermined period of time, the smaller the straight-line distance between the radiation emitter and the radiation receiver.
In some embodiments of the present invention, the receiver 300 includes a laser detector configured to receive the radiation (e.g., the laser beam) emitted from the radiation emitter 200. In an exemplary embodiment, the receiver 300 is in the form of an assembly that corresponds to the conceptual diagram presented on FIG. 48, with, by way of example, the serial communication being with processor 500. The receiver 300 may include biasing, threshold detection, AGC and/or adaptive threshold and/or gain control and digitizing electronic components. The receiver 300 may be configured to permit location detection in three dimensions. In an exemplary embodiment, the size of the aperture of the receiver 300 is such that three scan lines cross the detector (which is depicted as a diode detector) in FIG. 48 at the maximum usable range of the system. In some embodiments, it is sufficient that the aperture be configured such that a full single scan line will cross the detector.
According to the above, embodiments of the present invention may be implemented utilizing positioning areas and/or positioning volumes in a manner that will permit drogue positioning/station keeping to be implemented according to the present invention. In summary, any coordinate system may be utilized to practice the present invention.

Scaled Test Model

U.S. Provisional Patent Application Ser. No. 60/656,084, entitled Optical Tracking System for Refueling, filed on Feb. 25, 2005, the contents of which are incorporated herein by reference in its entirety, discloses, among other things, embodiments of the present invention configured for wind-tunnel scaled testing of at least some of the methods, devices, and systems as described herein. It is noted that the present invention thus includes the devices, systems and methods disclosed therein, scaled or unscaled. The present invention thus further includes the devices, systems and methods disclosed therein scaled for implementation with the teachings herein.
According to some embodiments of the scaled test model, the optical link is be visible and eye safe; the distance to the target may be about 10 feet, the active area of the scan beam (scanning area) may be about 12.8 inches by about 12.8 inches at the receiver; the grid resolution at the target may be about 0.025″; the beam spot size at the target may be about 0.015″ diameter or less; the frame rate may be about 100 Hz; the receiver active area may be about 0.250″ diameter or more; and the receiver may have a field of view of 30° (i.e. a conic included angle of 30°). Still further, according to some embodiments of the scaled test model, there may be 512×512 scan lines in a frame; there may be 18 bits minimum of encoding information on the beam for each position on the target grid such that (assuming 18 bits) a 26.2144 MHz data rate will be achieved, i.e., 512×512×100=26.2144 MHz data rate; encoding on the beam may be of a form that permits quick recognition that only a partial data frame has been received; sync and/or framing bits may be permitted, while recognizing that the data rate increases proportionally with the additional bits; and a single complete block of position data may take 0.78 μs. Such features may be scaled for implementation in a system as described herein for aerial refueling. By way of example, in some embodiments, it is expected that a frame (e.g., an complete horizontal and vertical scan) may be completed with a speed such that 20 frames/second may be accomplished. That is, one frame may be accomplished in 50 milliseconds. By way of example, a horizontal scan might take 20 milliseconds, and a vertical scan might take 20 milliseconds. If there were 500 rows/columns per scan, at 20 bits per row/column, 10,000 bits of information would be conveyed in 20 milliseconds.
As detailed herein, aircraft (including drogues, etc.) are subject to turbulence. In a scenario where the aircraft 1000 is subjected to turbulence, the radiation emitter 200 will likewise be subject to turbulence. In this regard, an embodiment of the present invention addresses this by providing a motion compensation system (see FIG. 57 for an example of a high-level control algorithm of the compensation system) such that, for example, grid displacement at 100 feet (slant range) is about +/−0.1 feet, and at 1800 feet slant range, the grid displacement is about +/−1.5 feet, in light turbulence.
The output of the receiver function may be an RS-232 data stream containing 3 bytes of data and running at 115.2 Kilo Baud. This data may be only the 18 bit position information without any sync or header bits. This message may be the code for the frame that is nearest the center of the receiver. This may be determined by analyzing all complete frames within the field of view of the receiver. This message stream may repeat at 100 Hz. Synchronization of the 3 byte frame may be either relative to the start of a complete scan frame or relative to the receiver processing element.
The transmitter may be self contained and may require only power applied to function. All beam forming, scanning, and modulation elements may be supplied. The transmitter may optionally be in two parts: an optical head; and an electronics assembly. Separation of up to 8 inches may be present between the optical head and the electronics if the transmitter is a two part unit.
The mounting on the receiver may have dynamic motion up to a frequency of 10 Hz; this motion may include both translation and rotation. Assuming an edge to edge motion over the 12.8 inch range at 10 Hz, the receiver will move 10 inches per 0.1 s. (i.e., at a rate of 100 inches per 1.0 s=0.0001 inches per 1.0 μs).
Although ambient light directed into the receiver may not be eliminated, it can be reduced or be made to be indirect. Moreover, although the receiver may be bandwidth limited by the use of optical filters, the operating wavelength may be in the visible band and, therefore, ambient light may still be present.
An exemplary implementation of an embodiment of the invention suitable for wind tunnel testing is as follows, and may be scaled accordingly for actual implementation.
A two-axis design may be utilized. Multiple optical paths, multiple scan configurations for a given optical path may be used. UV lasers or red lasers may be used. Single or dual galvanometer designs may be used. An internal line generator or an external line generator may be used. In fact, an “internal-external line generator” may be used, because without an internal line generator, the laser beam may be wide enough to appear on both the X and Y turning mirrors simultaneously, and thus appeared in the X and Y scan fields simultaneously. An internal line generator is thus useful, but the device may also have external line generating optics. Indeed, in some embodiments, a single galvo or dual galvo, either having internal LG optics, external LG optics or internal and external LG optics, may be utilized. A single galvo with internal line generator may be used, having three simple mirrors. Two sizes may be used: ½″×½″ and 1″×1″. Small line generation optics are used, with a simple optics mounting. FIGS. 26 to 31 schematically represent various galvo designs, while FIGS. 32 to 33 b schematically represent beam emission in elapsed time. It should be noted that the axis representations in these figures may not correspond exactly to those in the prior figures. In an exemplary embodiment, the radiation emitter includes a single line optical beam emitter, a prism, and a rotatable mirror assembly, wherein the radiation emitter is adapted to rotate the rotatable mirror assembly so that a single line optical beam emitted by the single line optical beam emitter is deflected by the mirror to project the emitted single line optical beam in a first orientation. The radiation emitter is further adapted to rotate the rotatable mirror assembly so that the single line optical beam emitted by the single line optical beam emitter passes through the prism to project the emitted single line optical beam in a second orientation different from the first orientation. In this manner, a single optical beam projector (e.g., laser) may be used instead of two projectors (laser generators). Of course, other embodiments of the present invention may utilize multiple generators that are synchronized to obtain lines at various orientations.
Regarding line quality and characteristics, to obtain a beam width of 0.25″ at 75 feet, using a UV laser diode with an emitting region of approximately one micron in width, a diffraction-limited cylindrical lens of at least 3 mm diameter is used, located at least 3 mm from the emitting region. Accordingly, a line width of 2 mm at a range of 8 feet, using a 635 nm laser, and a line width of 10 mm at 75 feet, with the same laser module may be obtained.
Since scanning may be done by a single axis scanner, rather than a tip-tilting plate, scans in the X and Y directions may have different virtual centers. The apparent sources of the X and Y scans are separated by approximately 9 mm in the X-direction, 13 mm in the Y-direction, and 13.5 mm in the Z direction (again, these axis may not correspond to those in the figures previously referred to herein). This has two effects on the scan registration at the sensor, both of which are minor at more than several feet working distance. The first effect is due to the apparent lateral separation of the sources. This parallax error results in the misregistration of the X- and Y-scans with changing ranges. The effect is about the same as what one would see if one held a flashlight in each extended hand, and aimed them at a single object. Objects both closer and farther away would register in different parts of the two beams. The effect is very small, though, since the virtual separation of the sources in the actual device is only about 16 mm. When the object is 8 feet away, the beam centers diverge at arctan(16/2400), or 0.38 degrees. This would result in a mis-registration of 1 mm for every 6 inches change in range. At a range of 75 feet, it would result in a mis-registration of 1 mm for every 56 inches change in range. Moreover, computers may be used to compensate for this. The only practical effect of this mis-registration is to reduce the coincident area over which both beams scan, as the range changes. Because the beams grow with range, the parallax error shrinks as a percentage of the area scanned. When the beams are aligned at 75 feet, this parallax error will cause the beams to overlap by only 90% when the range shrinks to 10 feet or so, 100% at 75 feet, and about 95% at one mile. For testing the system will be aligned at a range of 8 feet.
The second effect is due to the apparent longitudinal separation of the X and Y beam sources. This effect causes the Y beam to scan an area which is 1.3 mm larger than the X beam at any given range. This effect is negligible at all ranges where the beams are coincident.
The mirrors in the scanner are oriented to minimize errors of the scan. These errors take the form of coincidence errors, perpendicularity errors and keystone errors. Keystone errors cause the scan to travel farther along one edge than the other (the beam is actually sweeping out part of a large circle in the image plane), resulting in a keystone shaped scanned area. Perpendicularity errors cause the X and Y scans to travel at an angle other than 90 degrees to each other. Coincidence errors cause the centers of the X and Y scans to be non-coincident in the image plane. The result of these errors is to reduce the area of coincidence over which the X and Y scans travel and, in the case of perpendicularity errors, add crosstalk between the two axis. The mirrors are arranged so that all of these errors are normally either zero throughout the scan or at a minimum (zero) at the center of the scan.
Manufacturing errors in the mirror supports can move the orientations of the mirrors away from their designed positions, and thus cause the above-mentioned errors to become non-zero. Typical manufacturing errors are on the order of 0.003″. Assuming that each of the mirrors has a tilt error of this magnitude across its surface, the resulting scanned area at a range of 75 feet would be significantly reduced.
Manufacturing errors can be corrected by building into the device an X tilt adjustment on the X scan mirror and a Y tilt adjustment on the Y scan mirror. When those two adjustments are used to correct the manufacturing errors, the resulting scan can be restored to nearly its original condition. Even if some error, such as perpendicularity error, remains, as long as it is small, it may be effectively ignored.
The following material might be used to implement this embodiment: A fabricated XY scan mirror support block, a fabricated X scan mirror support block a fabricated Base, a fabricated Y scan mirror support block, a fabricated Laser support block, a fabricated Scanner support block a fabricated Laser aperture, a Thorlabs 2nd Y-scan mirror—ME1S-G01, a Thorlabs 1st Y-scan mirror—ME1S-G01, a Thorlabs X scan mirror—ME05S-G01, a Nuffield Technology, Inc. Scanner Mirror—10 mm X mirror, assembly, a Nuffield Technology, Inc. Scanner—Part No. HS-15C, a World Star Tech Laser Module—Part No. UTL5-10G-635.
FIGS. 34-39 present an example of a design for a scanner head, which is approximately 4×4×4 inches in dimension, although in other embodiments, the dimensions may be larger.
In some embodiments, the scan area is 2′×2′ at 12′ distance. Operation is at 25 Hz. FIGS. 34-39 schematically represent an emitter according to an embodiment of the present invention.
Again, the above may be scaled for actual implementation.
It is noted that while the above has been described in terms of application for determining a position of a refueling drogue relative to a reference point, and thus controlling the position of the refueling drogue relative to a refueling point, other embodiments of the present invention might be utilized to determine the location of other types of targets and/or control the location of those targets. Such targets may include, for example, aircraft, landcraft, boats, autonomous drones, satellites, a refueling boom extended from the refueling aircraft, etc. Indeed, some embodiments of the present invention may be implemented by placing a radiation emitter up on a tower, and scanning an area below the tower, such as a runway, a parking lot, a construction site, etc, and using the invention to control/position autonomous drones, autonomous vehicles (alleviating the need for a parking attendant), construction equipment such as bulldozers, etc.
In this regard, in an embodiment where the targets are aircraft (e.g., autonomous drones, a scan head may be placed on the aircraft 1000 so that the scan head will generate a modulated laser line as detailed herein. The mirror equipped galvanometer rotates a rotating mirror off of which the laser from the laser diode is reflected onto various fixed mirrors to generate the scan sweep. As may be seen, the scanner head includes three fixed mirrors. These fixed mirrors are used to form the grid detailed above. In this regard, referring now to FIGS. 44-46, in an exemplary embodiment, as the galvanometer mirror rotates clockwise, the laser beam from the laser diode is reflected from the rotating mirror onto a first mirror from which the beam is also reflected (see FIG. 44). Due to the rotation of the mirror, the reflected beam from the first mirror moves from right to left (hence the scan in the Y axis is produced). (Note that in this exemplary embodiment, the laser diode pulses at a rapid rate to form the grids of the Y axis scan.) As the rotating mirror continues to rotate clockwise, the laser line falls on the second mirror (see FIG. 45). The second mirror is oriented 45 degrees from the rotating mirror at this point, which causes the laser beam to project upward (relative to plane on which FIG. 45 is presented). The laser beam reflects from this second mirror onto a third mirror (see FIG. 46) which is tilted at a 45 degree angle in the X axis. The result of the three reflections is that the line formed by the laser beam is projected at a 90 degree angle with respect to the line that forms the scan in the Y axis.
The galvanometer of the exemplary embodiment depicted in FIGS. 43-46 is a linear current controlled torque motor with active positioning feedback that runs in a closed loop position control regime. In an exemplary embodiment, for a given current input, the galvanometer will rotate to a specific angle, and for a given current rate, the galvanometer will rotate at a specific rate. That is, in some embodiments, rotation of the galvanometer may be controlled by controlling the current and/or voltage to the galvanometer.
In some embodiments, the galvanometer is driven with a sawtooth waveform such that the galvanometer is swept through an active range in a linear manner, and then it is returned, or “flies back,” to the initial starting point (and thus the rotating mirror is so swept). FIG. 47 presents an exemplary graph showing galvanometer movement according to an embodiment of the present invention.
The radiation emitter 200 according to an exemplary embodiment of the present invention is mounted inside the aircraft 1000 (in some embodiments, it is a fully self contained unit requiring only power from the aircraft), and sometimes is mounted inside the pressure vessel of the aircraft, although in other embodiments, the emitter 200 may be mounted exteriorly to the aircraft and/or outside the pressure vessel. An exemplary embodiment of the emitter 200 transmits the scanning beams through a 2 inch diameter quartz aperture.
When used to scan other aircraft (e.g., a receiver aircraft, which may be a drone), it is expected that optical tracking may be executed at a range of at least about 1000 feet below and 1500 feet behind the aircraft 1000. In such an embodiment, a scan head that has a 30 degree field of view may be utilized. That is, the scan head outputs beams that scan through 30 degrees in each scan pass, although more narrow or broader fields of view (e.g., 20 degrees, 45 degrees, etc.) may be utilized depending on the desired performance characteristics of the optical tracking system. FIG. 50 presents exemplary fields of view of the scan head utilized in an exemplary embodiment of the optical tracking system according to the present invention (all dimensions are in feet unless otherwise indicated, and the schematic presented in FIG. 50 is to scale). In some embodiments, the optical tracking system outputs a UV laser beam that is safe with respect to a pilot of the other aircraft (e.g., safe to the pilots eyes, etc.). In this regard, FIG. 51 presents a performance characteristic of an embodiment of the optical tracking system according to a present invention, although it is noted that some embodiments need not adhere to this performance characteristic (e.g., in the case of tracking an autonomous drone, in the case of tracking a refueling drogue, etc.). Some embodiments operate at a maximum permissible exposure of 405 nM/185 mW. In some embodiments, the design of the scan head outputs radiation at an eye safe level per ANSI maximum permissible exposure levels. Some embodiments of the present invention are configured to operate in direct sunlight and in the presence of visible moisture. In this regard, FIGS. 52-54 present performance characteristics of some exemplary embodiments of the present invention. (Note that FIG. 54 presents visibility and signal transmission characteristics for various atmospheric conditions assuming a 45 degree field of view and a S/N Ratio>100.)
Some embodiments are NVG (night vision goggle) compatible, and have a low probability of detection/interception (e.g., in some embodiments, the scan beam is attenuated outside of a 3000 feet radius from the radiation emitter 200). The optical tracking system may provide a reference system independent of a global positioning system, intertial navigation system, etc.
Some embodiments of the present invention permit ease of calibration and include built in test features. In this regard, such features are related to the desire to obtain accurate beam modulation timing so that clock pulses are adequately synchronized in accordance with a saw-tooth waveform. (In an exemplary embodiment, the pulsation of the laser diode corresponds to a clock signal, and thus the pulsation may be considered a clock itself.) That is, the pulsation of the beam may be represented by a series of uniform square waves (see FIG. 59, for example). Along these lines, beam shift is believed to be the dominant error source in some embodiments of the present invention (due to, for example, temperature changes, galvanometer aging, mechanical damage/distortion, etc). Some embodiments are configured to compensate for beam shift by using, for example, by adjusting the drive electronics of the system. In some embodiments, an internal detector diode may be positioned at the mirror transition point in the emitter 200 to detect damage and/or significant drift of component(s) of the system. In some embodiments, the output waveform is monitored for compliance to a uniform square wave, uniform signal cycle gap, and/or equal number of edges on each side of the cycle gap, and waveform timing is adjusted to maintain some or all of these parameters. (FIG. 59 provides a schematic representation of an exemplary scenario where the system is calibrated/synchronized properly and is not calibrated/synchronized properly.) In some such embodiments, the function of maintaining some or all of these parameters provides a built in test capability that ensures that the galvanometer and laser are operating at a sufficient accuracy level.
It is noted that some embodiments of the present invention include a warning system to indicate to a user when the optical tracking system should and/or should not and/or should be used with caution.
FIG. 56 presents an exemplary performance characteristic of an embodiment of the optical tracking system according to the present invention, where it can be seen that range resolution is about 23.1 feet at 1803 feet from the radiation emitter 200, and that this resolution improves greatly the closer the target is to the emitter 200. (In an exemplary embodiment, range resolution improves by approximately 2 orders of magnitude as the distance between the radiation emitter 200 and the target decreases, and, in some embodiments, range resolution is less than about 1 inch at 100 feet.)
Given the disclosure of the present invention, one versed in the art would appreciate that there may be other embodiments and modifications within the scope and spirit of the present invention. Accordingly, all modifications attainable by one versed in the art from the present disclosure within the scope and spirit of the present invention are to be included as further embodiments of the present invention. The scope of the present invention accordingly is to be defined as set forth in the appended claims.

Claims

1. An airborne object tracking system, comprising:

an airborne object positioning system, the airborne object positioning system including a radiation emitter, a radiation receiver and a signal processor, wherein the radiation emitter is adapted to be attached to a refueling aircraft, and wherein the radiation receiver is adapted to attach to the airborne object;

wherein the radiation emitter is adapted to direct radiation to a positioning area a defined distance from the radiation emitter, the radiation carrying a modulated location signal containing information corresponding to positions within the positioning area;

wherein the radiation receiver is adapted to receive at least a portion of the emitted radiation carrying the modulated signal and output a signal to the signal processor indicative of the modulation of the location signal of the received radiation; and

wherein the signal processor is adapted to process the outputted signal and identify a position within the positioning area indicative of the location in the positioning area of the received radiation.

2. The system of claim 1, wherein the radiation emitter is adapted to emit a focused optical beam and scan the focused optical beam over the positioning area.

3. The system of claim 1, wherein the emitted radiation is a focused optical beam, wherein the modulated location signal includes a plurality of digital data blocks, the plurality of digital data blocks containing information respectively corresponding to a plurality of discrete positions within the positioning area that respectively correspond to a current location of the focused beam within the positioning area.

4. The system of claim 3, wherein the radiation emitter is adapted to emit a focused optical beam and scan the focused optical beam over the positioning area.

5. The system of claim 2, wherein the radiation emitter is adapted to emit a focused optical beam and scan the focused optical beam over the positioning area in an X-Y raster.

6. The system of claim 2, wherein the radiation emitter is adapted to emit a focused optical elongated beam and scan the focused optical elongated beam over the positioning area in a dual-pass manner.

7. The system of claim 2, wherein the radiation emitter is adapted to emit a focused optical beam and scan the focused optical beam over the positioning area in a spiral pattern, the spiral pattern having a focus at the approximate center of the positioning area.

8. The system of claim 3, wherein the radiation receiver is adapted to receive at least a portion of the focused beam when at least that portion of the focused beam is directed at the radiation receiver, and wherein the signal outputted by the receiver is indicative of the information contained in at least one digital data block carried by the received radiation.

9. The system of claim 3, wherein the radiation receiver is adapted to receive at least a portion of the focused beam when at least that portion of focused beam is directed at the radiation receiver and determine whether a full digital data block carried by the focused beam has been received, and only if a full digital data block has been received, output the signal to the signal processor, wherein the outputted signal is indicative of the information contained in the full digital data block received.

10. The system of claim 1, wherein the radiation emitted by the radiation emitter is a focused beam and the radiation emitter is adapted to scan the focused beam over the positioning area;

wherein the airborne object positioning system is adapted to virtually divide at least a portion of the positioning area into a virtual grid, the virtual grid including a plurality of distributed distinct sectors, the distributed distinct sectors spatially corresponding to sub-areas within the positioning area, the sub-areas being disbursed within the positioning area in a geometrically defined manner;

wherein the airborne object positioning system is adapted to change the modulated location signal carried on the focused beam as the focused beam is scanned over the positioning area, wherein change in the modulated location signal corresponds in a defined manner to the sub-areas such that a modulated location signal indicative of a beam being directed at a first sub-area is distinct from a modulated location signal indicative of a beam being directed at a second sub-area; and

wherein the signal processor is adapted to analyze one or more outputted signals from the receiver indicative of the modulation of the location signal and identify a distinct sector corresponding to the received modulated location signal carried on the focused beam.

11. The system of claim 10, wherein the signal processor identifies a sub-area at which the beam is directed based on the identification of the distinct sector corresponding to the received modulated location signal carried on the emitted radiation.

12. The system of claim 10, wherein the signal processor is adapted to analyze a first outputted signal and a second outputted signal outputted after the first outputted signal to determine a location in the virtual grid at which the distinct sectors coincide; the first and second outputted signals being respectively indicative of the modulation of the location signal of the beam received by the receiver.

13. The system of claim 12, wherein the signal processor identifies a sub-area at which the beam is directed based on the determination of the location in the virtual grid at which the distinct sectors coincide.

14. The system of claim 12, wherein the radiation emitted by the radiation emitter is a focused optical elongated beam and the radiation emitter is adapted to scan the focused optical elongated beam over the positioning area in a dual-pass manner, wherein the first outputted signal is generated by the reception of at least a portion of the focused optical elongated beam in a first pass of the beam over the positioning area, and wherein the second outputted signal is generated by the reception of at least a portion of the focused optical elongated beam in a second pass of the beam over the positioning area.

15. The system of claim 14, wherein the focused optical elongated beam of the first pass is normal to the focused optical elongated beam of the second pass.

16. The system of claim 14, wherein the airborne object positioning system is adapted to identify the location of the receiver within the positioning area based on the coincidence of the first optical elongated beam and the second optical elongated beam.

17. The system of claim 1, wherein the system is part of a system assembly that includes an aerial refueling system that includes an aerial refueling device that in turn includes an active control system adapted to regulate a position of the aerial refueling device with respect to a refueling aircraft when the aerial refueling device is extended from the refueling aircraft.

18. The system of claim 11, wherein the radiation receiver is mounted on the airborne object, wherein the airborne object includes an active control system adapted to regulate the position of the radiation receiver within the positioning area when the airborne object is proximate a refueling aircraft on which the radiation emitter is mounted.

19. The system of claim 18, wherein the active control system is adapted to regulate the vertical and horizontal position of the airborne object to maintain a substantially fixed orientation of the receiver within the positioning area.

20. The system of claim 17, wherein the active control system is adapted to regulate a position of the radiation receiver so that the position of the radiation receiver is substantially constant within the positioning area.

21. An airborne object tracking system, comprising:

an airborne object positioning system, the airborne object positioning system including a radiation emitter adapted to be attached to a refueling aircraft, and a radiation receiver adapted to be attached to the airborne object, and a signal processor;

wherein the radiation emitter is adapted to direct a beam of emitted radiation to an area away from the radiation emitter, the radiation including discernable properties that vary in a corresponding manner with varying orientation of the beam of radiation with respect to the radiation emitter;

wherein the radiation receiver is adapted to receive at least a portion of the emitted radiation and output a signal to the signal processor indicative of one or more of the discernable properties of the received radiation; and

wherein the processor is adapted to process the outputted signal and identify a first virtual orientation indicative of an orientation of the receiver relative to the radiation emitter when at least a portion of the radiation was received by the receiver.

22. The system of claim 21, wherein the radiation emitter is adapted to emit a focused optical beam modulated with digital data blocks, the modulated digital data blocks respectively indicative of discrete orientations respectively corresponding to orientations of the beam relative to the radiation emitter.

23. The system of claim 22, wherein at least some of the varied discernable properties are respectively indicative of discrete orientations respectively corresponding to orientations of the beam relative to the radiation emitter in a first reference frame, and wherein at least some of the varied discernable properties are respectively indicative of discrete orientations respectively corresponding to orientations of the beam relative to the radiation emitter in a second reference frame.

24. The system of claim 23, wherein the signal processor is adapted to analyze a first outputted signal from the receiver, the first outputted signal being indicative of a first discernable property of the received radiation indicative of a first discrete orientation corresponding to a first orientation of the beam relative to the radiation emitter in the first reference frame at the time that the radiation was received, and wherein the signal processor is adapted to analyze a second outputted signal from the receiver, the second outputted signal being indicative of a second discernable property of the received radiation indicative of a second discrete orientation corresponding to a second orientation of the beam relative to the radiation emitter in the second reference frame at the time that the radiation was received; and

wherein the signal processor is adapted to identify a virtual location of the receiver relative to the radiation emitter based on the analysis of the first and second outputted signals.

25. The system of claim 22, wherein the radiation receiver is adapted to receive the focused beam carrying the digital data blocks when the focused beam is directed at the radiation receiver and output the signal to the signal processor, wherein the outputted signal is indicative of the information contained in a digital data block carried on the received beam, and wherein the processor is adapted to analyze the outputted signal from the receiver indicative of the information contained in the received digital data block and identify the orientation of the beam relative to the radiation emitter based on the information contained in the received digital data block to identify the first virtual orientation.

26. The system of claim 21, wherein the radiation emitted by the radiation emitter is a focused beam and the radiation emitter is adapted to scan the focused beam over the area;

wherein the airborne object positioning system is adapted to virtually divide at least a portion of the various possible orientations of the beam relative to the radiation emitter into a beam zone, the beam zone including a plurality of distributed distinct vectors, the distributed vectors spatially corresponding to actual orientations of the beam with respect to the radiation emitter, the actual orientations being disbursed within the beam zone in a geometrically defined manner;

wherein the radiation emitter is adapted to change the modulated signal carried on the focused beam as the focused beam is scanned over the area to obtain different modulated signals, the different modulated signals corresponding in a defined manner to the actual orientations such that a modulated signal indicative of a beam being directed along a first orientation is distinct from a modulated signal indicative of a beam being directed along a second orientation; and

wherein the signal processor is adapted to analyze the outputted signal from the receiver indicative of the modulation of the signal and identify the distinct vector corresponding to the received modulated signal carried on the emitted radiation.

27. The system of claim 26, wherein the signal processor is adapted to identify the orientation of the receiver relative to the radiation emitter based on the identified distinct vector.

28. The system of claim 26, wherein the signal processor determines at least one of (i) the distinct vector along which the beam is directed based on the identification of the distinct vector corresponding to the received modulated signal carried on the emitted radiation and (ii) the orientation along which the beam is directed based on the identification of the distinct vector corresponding to the received modulated signal carried on the emitted radiation.

29. The system of claim 21, wherein the airborne object includes an active control system adapted to regulate the position of the airborne object with respect to a refueling aircraft on which the radiation emitter is mounted when the airborne object is proximate the refueling aircraft.

30. The system of claim 29, wherein the radiation receiver is mounted on the airborne object, wherein the aerial refueling system includes an active control system adapted to regulate the position of the radiation receiver when the airborne object is proximate a refueling aircraft on which the radiation emitter is mounted.

31. The system of claim 29, wherein the active control system is adapted to regulate the vertical and horizontal position of the airborne object to maintain a substantially fixed orientation of the receiver with respect to the radiation emitter.

32. A method of determining a position of an airborne object, comprising:

positioning an airborne object proximate a refueling aircraft;

scanning a focused optical elongated beam from a radiation emitter onboard the refueling aircraft over a positioning area a defined distance from the radiation emitter;

modulating a signal carried on the beam as the beam is scanned over the positioning area in a manner corresponding to positions of the beam within the positioning area;

receiving the optical beam carrying the modulated signal with a receiver on the airborne object; and

analyzing the modulation of the signal carried on the received optical beam to determine a position within the positioning area of the receiver at the time the radiation was received.

33. The method of claim 32, further comprising scanning the focused optical elongated beam over the positioning area in a two-pass manner and receiving the focused elongated beam scanned in a two-pass manner.

34. The method of claim 33, further comprising receiving the optical beam scanned in a first pass of the two-pass scan and receiving the optical beam scanned in a second pass of the two-pass scan and comparing the beams received in the first pass and the second pass and determining the position of the receiver within the positioning area based on a correspondence of position of the beams within the positioning area of the beams.

35. The method of claim 33, further comprising receiving the optical beam scanned in a first pass of the two-pass scan and receiving the optical beam scanned in a second pass of the two-pass scan and comparing the beams received in the first pass and the second pass and determining the position of the receiver within the positioning area based on a correspondence of position of the received beams within the positioning area.

36. The method of claim 32, further comprising actively controlling the airborne object to maintain a substantially fixed position relative to the radiation emitter based on the determined position within the positioning area of the receiver.

37. The system of claim 1, wherein the radiation emitter includes:

a single line optical beam emitter;

a prism; and

a rotatable mirror assembly;

wherein the radiation emitter is adapted to rotate the rotatable mirror assembly so that a single line optical beam emitted by the single line optical beam emitter is deflected by the mirror to project the emitted single line optical beam in a first orientation; and wherein the radiation emitter is adapted to rotate the rotatable mirror assembly so that the single line optical beam emitted by the single line optical beam emitter passes through the prism to project the emitted single line optical beam in a second orientation different from the first orientation.

38. The system of claim 1, wherein the system is part of a system assembly that includes an aerial refueling device adapted to transfer fuel to a receiver aircraft extendable from a refueling aircraft.

39. The system of claim 38, wherein the aerial refueling device comprises a refueling drogue assembly including a refueling drogue and a refueling hose in captive relation with the refueling drogue, and wherein the radiation receiver is mounted on at least one of the refueling drogue and the refueling hose.

40. The system of claim 38, wherein the aerial refueling device comprises a refueling boom assembly, and wherein the radiation receiver is mounted on the refueling boom.

41. The system of claim 1, wherein the system is adapted to extract information from the radiation emitted from the radiation emitter which is received by the radiation receiver indicative of a straight-line distance between the radiation emitter and the radiation receiver.

42. The system of claim 41, wherein the system is adapted to extract information from the radiation emitted from the radiation emitter which is received by the radiation receiver indicative of a straight-line distance between the radiation emitter and the radiation receiver, the information being based on the amount of radiation received by the radiation receiver during a predetermined period of time, the system including an algorithm having the parameters such that the more radiation from the radiation emitter that is received by the radiation receiver during the predetermined period of time, the smaller the straight-line distance between the radiation emitter and the radiation receiver.

43. The system of claim 41, wherein the radiation emitter modulates an intensity of the beam according to a periodic cycle, wherein the system is adapted to extract information from the radiation emitted from the radiation emitter which is received by the radiation receiver indicative of a straight-line distance between the radiation emitter and the radiation receiver, the information being based on the number of modulations detected by the radiation receiver during a predetermined period of time, the system including an algorithm having the parameters such that the greater the collective intensity of radiation from the radiation emitter that is received by the radiation receiver during the predetermined period of time, the smaller the straight-line distance between the radiation emitter and the radiation receiver.

44. The system of claim 41, wherein the radiation emitter cycles emission of the beam according to a periodic cycle to direct a plurality of lines towards the radiation receiver, wherein the system is adapted to extract information from the radiation emitted from the radiation emitter which is received by the radiation receiver indicative of a straight-line distance between the radiation emitter and the radiation receiver, the information being based on the number of emission cycles detected by the radiation receiver during a predetermined period of time, the system including an algorithm having parameters such that the higher number of emission cycles from the radiation emitter that are received by the radiation receiver during the predetermined period of time, the smaller the straight-line distance between the radiation emitter and the radiation receiver.

45. The system of claim 21, wherein the system is part of a system assembly that includes an aerial refueling device adapted to transfer fuel to a receiver aircraft extendable from a refueling aircraft.

46. The system of claim 45, wherein the aerial refueling device comprises a refueling drogue assembly including a refueling drogue and a refueling hose in captive relation with the refueling drogue, and wherein the radiation receiver is mounted on at least one of the refueling drogue and the refueling hose.

47. The system of claim 45, wherein the aerial refueling device comprises a refueling boom assembly, and wherein the radiation receiver is mounted on the refueling boom.

48. The system of claim 21, wherein the system is adapted to extract information from the radiation emitted from the radiation emitter which is received by the radiation receiver indicative of a straight-line distance between the radiation emitter and the radiation receiver.

49. The system of claim 48, wherein the system is adapted to extract information from the radiation emitted from the radiation emitter which is received by the radiation receiver indicative of a straight-line distance between the radiation emitter and the radiation receiver, the information being based on the amount of radiation from the radiation emitter received by the radiation receiver during a predetermined period of time, the system including an algorithm having the parameters such that the more radiation from the radiation emitter that is received by the radiation receiver during the predetermined period of time, the smaller the straight-line distance between the radiation emitter and the radiation receiver.

50. The system of claim 48, wherein the radiation emitter modulates an intensity of the beam according to a periodic cycle, wherein the system is adapted to extract information from the radiation emitted from the radiation emitter which is received by the radiation receiver indicative of a straight-line distance between the radiation emitter and the radiation receiver, the information being based on the number of modulations of the radiation from the radiation emitter detected by the radiation receiver during a predetermined period of time, the system including an algorithm having the parameters such at least one of:

the greater the collective intensity of radiation from the radiation emitter that is received by the radiation receiver during the predetermined period of time, the smaller the straight-line distance between the radiation emitter and the radiation receiver;

the greater the number of modulations of the radiation from the radiation emitter that is received by the radiation receiver during the predetermined period of time, the smaller the straight-line distance between the radiation emitter and the radiation receiver.

51. The system of claim 48, wherein the radiation emitter cycles emission of the beam according to a periodic cycle to direct a plurality of lines towards the radiation receiver, wherein the system is adapted to extract information from the radiation emitted from the radiation emitter which is received by the radiation receiver indicative of a straight-line distance between the radiation emitter and the radiation receiver, the information being based on the number of emission cycles detected by the radiation receiver during a predetermined period of time, the system including an algorithm having parameters such that the higher number of emission cycles of the radiation from the radiation emitter that are received by the radiation receiver during the predetermined period of time, the smaller the straight-line distance between the radiation emitter and the radiation receiver.

52. The method of claim 32, wherein the airborne object is a receiver aircraft.

53. The method of claim 32, further comprising:

positioning a second airborne object proximate the refueling aircraft;

receiving the optical beam carrying the modulated signal with a second receiver on the second airborne object; and

analyzing the modulation of the signal carried on the received optical beam to determine a position within the positioning area of the second receiver at the time the radiation was received.

54. The method of claim 53, wherein the actions are performed within five seconds of one another.

55. The method of claim 32, further comprising:

positioning a second airborne object proximate the refueling aircraft;

scanning a second focused optical elongated beam from a second radiation emitter onboard the refueling aircraft over a second positioning area a respective defined distance from the radiation emitter;

modulating a signal carried on the second beam as the second beam is scanned over the second positioning area in a manner corresponding to positions of the second beam within the second positioning area;

receiving the second optical beam carrying the second modulated signal with a second receiver on the second airborne object; and

analyzing the modulation of the second signal carried on the received second optical beam to determine a position within the second positioning area of the second receiver at the time the second radiation was received.

56. The method of claim 55, wherein the actions are performed within 5 seconds of one another.

57. The method of claim 55, wherein at least a portion of the second positioning area overlaps at least a portion of the first positioning area.

58. The method of claim 32, further comprising:

scanning a second focused optical elongated beam from a second radiation emitter onboard the refueling aircraft over a second positioning area a defined distance from the radiation emitter;

receiving the second optical beam carrying the second modulated signal with the receiver on the airborne object; and

59. The method of claim 58, wherein the first and second positioning areas at least one of partially overlap and fully overlap, the method further comprising comparing the determined position within the first positioning area to the determined position within the second positioning area to evaluate accuracy.

60. The method of claim 58, wherein the actions are performed within 5 seconds of one another.

61. A method of positioning an airborne object relative to a refueling aircraft, comprising:

executing the actions of claim 32; and

varying the position of at least one of the airborne object an at least a component of the refueling aircraft adapted to mate with the airborne object based on the determined position of the receiver within the positioning system to decrease a range between the airborne object and the component of the refueling aircraft adapted to mate with the airborne object until the airborne object and the component of the refueling aircraft adapted to mate with the airborne object mate with one another.

62. A method of positioning an airborne object relative to a refueling aircraft, comprising:

executing the actions of claim 32; and

automatically varying the position of at least one of the airborne object an at least a component of the refueling aircraft adapted to mate with the airborne object based on the determined position of the receiver within the positioning system to automatically decrease a range between the airborne object and the component of the refueling aircraft adapted to mate with the airborne object until the airborne object and the component of the refueling aircraft adapted to mate with the airborne object mate with one another.

63. The method of claim 32, wherein the airborne object is an autonomous drone.