Patent Publication Number: US-8536501-B2

Title: Virtually attached node

Description:
RELATED APPLICATION 
     This patent application is related to concurrently-filed U.S. patent application Ser. No. 10/691,324 having title “LASER-TETHERED VEHICLE,” having filing date 22 Oct. 2003, having issue date 18 Oct. 2005 and having U.S. Pat. No. 6,955,324, which is incorporated by reference. 
     FIELD OF THE INVENTION 
     This invention relates generally to unmanned craft and, more specifically, to remotely controlled vehicles. 
     BACKGROUND OF THE INVENTION 
     Remote-controlled vehicles, particularly Unmanned Air Vehicles (UAVs), have been in use for years for many different applications. At a simple end, hobbyists steer remote-controlled cars or boats or fly remote-controlled airplanes for entertainment. At a sophisticated end, military and intelligence agencies fly UAVs to conduct surveillance in hostile territories. UAVs are equipped with cameras, microphones, and other sensors to gather intelligence. These sophisticated, complex UAVs are controlled from remote stations. 
     Control of such devices can be a complex problem. Even high-end hobbyist UAVs have control panels that cannot be practically hand held because of the many levers, dials, switches, and other control devices the operator uses to direct such a device. Moreover, transmitting the control information from the many control devices, receiving and decoding the instructions at the remote device, and executing the instructions represent involved data communication problems. 
     In addition, a limitation particularly limiting UAVs is that, like manned aircraft, a UAV has to have the capacity to carry enough fuel or power to complete its mission. The longer the mission, the more fuel or power that must be carried, and, the larger the UAV must be to carry its own source of power. Furthermore, hovering tends to consume substantially more power than forward flight. Thus, UAVs commonly use fixed-wing, forward flight designs. 
     For example, the Pointer by AeroVironment is a fixed-wing UAV. The Pointer has a length of 6 feet with a wingspan of 9 feet. The Pointer weighs 8 pounds with a payload of 2 pounds and a battery weighing 2.2 pounds. It is hand-launched by being thrown into the air. The Pointer has a flight duration of 1.5 hours with a range of 5 miles. 
     However, forward-flight is not an optimal flight mode for all purposes. For example, forward-flight is not an optimal flight mode for surveillance. A forward-flying platform moves over and may move past targets of interest. While a forward-flying platform can circle a target of interest, gathering information about the target may be complicated by moving a camera lens or other directional sensor to focus on the target. As a result, a hovering platform presents a more desirable point from which to observe a target of interest. Forward-flight also is not optimal for a platform to be used for relaying or redirecting signals. For these purposes it would be advantageous to have a hovering platform suspended over a stationary ground point to redirect and relay signals for which a line-of-sight transmission is desirable but not possible. Such a hovering platform would enable communications or other electromagnetic transmission to be broadcast over buildings or other barriers that ordinarily would block such transmissions. 
     Hovering vehicles generally consume more power than forward-flying vehicles. To try to develop a more efficient hovering vehicle, micro air vehicles (MAVs) have been created using flapping wing technologies to create lift. The existence of insects and small flying animals suggests that flapping wing technologies can be an efficient way to create lift. For one example, a collaboration between Caltech and UCLA has developed an MAV called the MicroBat. The MicroBat recently broke the world record in flapping wing flight of an MAV with a flight lasting only 6 minutes and 17 seconds. The MicroBat carries a polymer lithium ion battery as its power source and carries a radio transceiver. The total weight of the MicroBat is only 12 grams. However, in flapping wing flight, aerodynamic flow properties are complex and difficult to manage. Thus, just as land-based vehicles tend not to be based on walking movements of bipeds or quadrupeds but on simpler-to-manage rotating motivators such as wheels, it would be simpler to effect hovering using a rotary wing design such as a helicopter. Unfortunately, an efficient way to sustain hovering flight for very long intervals has proven elusive. 
     Thus, there is an unmet need in the art for facilitating sustained, hovering flight and thereby allowing for simpler and more efficient ways to perform aerial surveillance of a target of interest or to redirect and relay electromagnetic signals from a transmission site to a receiver or other target. 
     SUMMARY OF THE INVENTION 
     The present invention provides a system and method for operating a remote-controlled vehicle and a remote-controlled vehicle operated according to the system and method. A preferred embodiment of the present invention includes an unmanned vehicle (UAV) configured to be directable to a point of interest and hover over the point of interest. In contrast with known hovering vehicles that include relatively complex control schemes to maintain the vehicle in a desired position, embodiments of the present invention are guided and powered by an electromagnetic beam generated from a ground source or an aircraft. Using electromagnetic sensors on the vehicle to monitor the position of the electromagnetic beam, the vehicle tracks the position of the electromagnetic beam. Thus, by controlling the position of the electromagnetic beam, the position of the airborne vehicle can be controlled, thereby allowing for surveillance of a desired location or a signal relay point to be positioned at a desired point in space. Other embodiments of the present invention also convert the received electromagnetic energy beam into electrical power for providing at least a portion of the power used in operating the vehicle. 
     More particularly, embodiments of the present invention provide a position control system for a remote-controlled vehicle. An electromagnetic energy receiver is configured to receive an electromagnetic beam. The electromagnetic energy receiver is further configured to determine a position of the remote-controlled vehicle relative to a position of the electromagnetic beam. The vehicle is directed to maneuver to track the position of the electromagnetic beam. 
     In accordance with other aspects of the present invention, the electromagnetic energy receiver includes at least one photoelectric cell configured to generate electrical power when subjected to application of electromagnetic energy. The photoelectric cell may include a solar cell. The electromagnetic energy receiver may be configured to receive an externally-applied laser signal. 
     In accordance with still further aspects of the present invention, the electromagnetic energy receiver includes an electromagnetic receiving array including a plurality of electromagnetic sensors. Each of the electromagnetic sensors is configured to generate a sensor output indicative of an intensity of electromagnetic energy received by the electromagnetic sensor. The vehicle is maneuvered to generally equalize the sensor output of each of the electromagnetic sensors by maneuvering the remote-controlled vehicle such that the electromagnetic beam is received toward a center of the electromagnetic receiving array. The vehicle is further maneuvered relative to the source of the electromagnetic beam such that the remote-controlled vehicle maintains a predetermined distance from the source of the electromagnetic beam. The control system is further configured to receive external commands for adjusting a response to the electromagnetic beam. 
     Additionally, in accordance with other aspects of the present invention, the remote-controlled vehicle may include an airborne vehicle, including a rotor-lifted vehicle powered by one or more rotors or a lighter-than-air vehicle, a land-based vehicle, a water-based vehicle, or a space-based vehicle. 
     In accordance with still further embodiments of the present invention, the vehicle may include at least one surveillance device. The surveillance device suitably is configured to capture data from the perspective of the remote-controlled vehicle. The surveillance device also suitably is configured to transmit telemetry to a telemetry station and/or is remotely controllable from a control station. The surveillance device may include at least one of a camera, a microphone, a chemical sensor, a biological sensor, a radiation detector, and an environmental sensor. The vehicle also may include a payload delivery mechanism. The vehicle may have a means to modulate and rebroadcast the received electromagnetic power to relay information back to the source of that power or control station. Alternatively, the vehicle may include an electromagnetic relay device configured to relay an electromagnetic signal from a signal source to a signal destination. The relay device may include an electromagnetic signal such as a communication signal or an energy weapon. The relay device may include a reflector or a relay device such as a microwave relay. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The preferred and alternative embodiments of the present invention are described in detail below with reference to the following drawings. 
         FIG. 1  is a top view of a laser-tethered airborne device according to an embodiment of the present invention; 
         FIG. 2  is a side view of the device of  FIG. 1 ; 
         FIG. 3  is a perspective view of the device of  FIG. 1 ; 
         FIG. 4  is a perspective view of the device powered and controlled by a ground station; 
         FIG. 5  is a laser-tethered airborne device according to another embodiment of the present invention; 
         FIG. 6  is a zone diagram of a laser receiving array of the device; 
         FIG. 7  is a block diagram of a laser receiving and control device used by an embodiment of the present invention; 
         FIG. 8  is a yaw control device used by an embodiment of the present invention; 
         FIG. 9  is a block diagram of a control system used by an embodiment of the present invention; 
         FIG. 10  is a diagram illustrating an embodiment of the present invention in which an airborne vehicle is tethered by an electromagnetic beam and is configured to relay an electromagnetic signal; 
         FIG. 11  is a side-elevational view of an alternative embodiment of the present invention used with a lighter-than-air vehicle; 
         FIG. 12  is a perspective view of the vehicle of  FIG. 11  being controlled by an electromagnetic beam; and 
         FIG. 13  is a flowchart of a routine for using an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     By way of overview, embodiments of the present invention provide a method for remote powering and a position control system for a remote-controlled vehicle. An electromagnetic energy receiver is configured to receive an electromagnetic beam. The electromagnetic energy receiver is further configured to determine a position of the remote-controlled vehicle relative to a position of the electromagnetic beam. The vehicle is directed to maneuver to track the position of the electromagnetic beam. 
       FIG. 1  is a perspective view of a laser-tethered airborne device  100 . The device  100  includes a structure or housing  110  which supports a propulsion system including a plurality of rotors  120 . In one presently preferred embodiment, the rotors  120  are disposed to rotate so as to generate thrust in a direction opposed to a gravitational force. One presently preferred embodiment includes a plurality of rotors  120  that are disposed at a distance around a center of gravity of the device  100 . The rotors  120  each are individually controlled by a positioning control system (not shown). The speed and resultant thrust generated by each of the rotors  120  can be manipulated to generate a composite thrust having components directed both against the gravitational force and perpendicular to the gravitational force to control the altitude and azimuth of the device  100  relative to a position on the ground. Alternatively, the device  100  could be powered by one or more rotors  120 . The one or more rotors are disposed to rotate in a plane and thereby generate thrust. The provided thrust provides lift against the gravitational force and one or more rotors disposed in a perpendicular plane to provide thrust perpendicular to the gravitational force. Further alternatively, gimbaled rotors (not shown) could be used to generate thrust to provide lift against the gravitational force and thrust perpendicular to the gravitational force. 
     A rotor-powered craft could include a rotor speed optimization system such as that disclosed in U.S. Pat. No. 6,007,298 for an “optimum speed rotor” for improved rotorcraft performance, which is assigned to the assignee of the present invention and incorporated by reference. Use of such a system would allow for optimization of rotor speed in order to provide desired rotor output and reduce unnecessary power consumption. 
     An electromagnetic energy receiver  130  is disposed on the housing  110  to receive an electromagnetic beam  140 . Details of the electromagnetic beam are set forth below. The electromagnetic energy receiver  130  is configured to convert energy contained in the electromagnetic energy beam  140  into electrical power. The converted electrical power provides energy to drive the rotors  120 , the positioning control system (not shown), and other on-board systems on the device  100 . As a result of the electrical power being provided from a source outside the device  100 , the device is operable to maintain controlled flight and support other functions without an on-board power supply such as a battery, a fuel cell, or another power plant that would add size and, more pertinently, add mass and weight to the device  100 . As previously described, adding mass to the device  100  is highly undesirable because additional mass dictates additional thrust requirements which, in turn, result in additional equipment mass to generate the additional thrust. In other words, beaming power to the device  100  allows the device  100  to be advantageously small and lightweight to reduce the cross-sectional target presentation, complexity, and cost of the device  100 . 
     The electromagnetic energy receiver  130  and the positioning control receiver are further configured to respond to a projected position of the electromagnetic beam  140 . As will be further described below, in one presently preferred embodiment the electromagnetic energy receiver  130  includes a plurality of photocells, such as solar cells, to receive the electromagnetic beam  140  and generate electrical power. In one presently preferred embodiment, the electromagnetic beam receiver  130  includes GaSb and Ge cells. These cells are available with quantum efficiencies as high as around 95%. Other photocells, including InGaAsP or InP photocells also provide suitable power conversion in desirable operating ranges that are described further below. 
     An electromagnetic beam  140  at a wavelength of 1.064 μm provides a workable solution, as will be further described below. At this wavelength, a number of solar cell types can be used to collect energy for the device. Of these, two types currently are readily available solar cells widely used in the infrared range. A Ge solar cell is often used as the bottom cell in high efficiency multi-junction solar cells, mainly for space applications. A GaSb solar cell is commonly used in thermo-photovoltaic applications. Although the Ge and GaSb cells are widely available, their energy conversion efficiencies are not particularly high because both have bandgaps that are slightly lower than an optimal level. In general, to get good conversion efficiencies the semiconductor band gap would have to be smaller but close in energy to that of the incident radiation. For example, a bandgap smaller than 1.064 eV is desirable for an energy source having a wavelength of 1.064 μm. Ge cells have an efficiency of approximately 16% whereas GaSb actually have a slightly higher efficiency of approximately 20% even though Ge cells have a more favorable bandgap. Better conversion efficiencies would be possible at the 1.064 μm wavelength with the solar cells made of a semiconductor with a bandgap closer to 1.05 eV. Such cells are not commercially available but could be created using a material of composition In 0.85 Ga 0.15 As 0.4 P 0.6  grown on an InP substrate. Such a cell could provide a total conversion efficiency of up to 43% with a fill factor of 83%. 
     Also, the use of a plurality of photocells allows the positioning control system (not shown) coupled with the electromagnetic energy receiver  130  to respond to a projected position of the electromagnetic beam  140 . More specifically, each of the photocells included in the electromagnetic energy receiver  130  are operable to generate electrical power in proportion to a specific intensity of the electromagnetic beam  140  striking each of the photocells. Accordingly, the positioning control system (not shown) can be programmed to control the propulsion system to balance the power output of the photocells in the electromagnetic energy receiver  130  by a suitable adjustment of the vehicle position. 
     For example, the positioning control system (not shown) suitably controls the propulsion system to maintain a position of the device  100 . The positioning control system (not shown) suitably is programmed to balance a vertical and horizontal attitude such that the power output of the photocells is approximately equal. Similarly, the positioning control system (not shown) suitably is programmed to maintain a composite energy output of the photocells in the electromagnetic energy receiver  130 . As a result, the positioning control system (not shown) can maintain the device  100  at a distance and an attitude relative to the received electromagnetic beam  140  such that the electromagnetic beam  140  serves as a virtual tether for the device  100 . 
     According to one exemplary embodiment, the device  100  is equipped with at least one array  150  of photocells, such as solar cells, disposed to receive ambient electromagnetic energy and convert it to auxiliary electrical power to power on-board systems of the device  100 . The photocell arrays  150  suitably include Si solar cells coupled with capacitors to provide a backup power source. The auxiliary electrical power provided by the photocell arrays  150  suitably is used to provide additional or backup power for the device. For example, if the device  100  loses contact with the electromagnetic beam  140  for any reason, the positioning control system (not shown) can use the auxiliary electrical power to bring the device to a soft, controlled landing. In one presently preferred embodiment, the positioning control system (not shown) will slowly lower the device  100  to earth and/or drive the device  100  toward the source of the electromagnetic beam  140  to reestablish the power link between the device  100  to its base. 
     One presently preferred embodiment of the device is a substantially disk-shaped object about 12-14 inches in diameter with the electromagnetic energy receiver  130  on one side. The size of the vehicle is chosen so as to minimize the power utilized for remote powered flight. One presently preferred embodiment includes four electrically-powered brushless DC motors to drive the rotors  120 . A four-rotor design is used because it simplifies the control system for the device. By varying the torque applied to the four rotors  120 , roll, pitch, yaw, and overall thrust can be controlled. This strategy for control is feasible for a small size craft because the rotor inertia is very low and the control bandwidth is very high. If desired, additional damping suitably is provided by gyroscopic feedback. 
       FIG. 2  shows the device  100  receiving the electromagnetic beam  140  from a control station  200 . In one exemplary embodiment, the control station  200  suitably is a ground-based vehicle, although the control station  200  could be a fixed, ground-based control station, an aerial control station such as a helicopter or other flying platform or a naval vehicle. The control station  200  includes a beam generator  210  for generating the electromagnetic beam  140 . As previously described, the electromagnetic beam  140  suitably serves as a tether for the device. Thus, by steering the beam generator  210 , operators of the control station  200  can position the device  100  in altitude and azimuth. As the positioning control system (not shown) of the device will strive to equalize the electrical power output of the photocells in the electromagnetic energy receiver  130  ( FIG. 1 ), the device  100  will move to follow the projection of the electromagnetic energy beam. In one presently preferred embodiment, the beam generator  210  is a laser generator. The power output of the laser generator suitably is balanced to provide sufficient power for the device  100  ( FIG. 1 ) without generating a destructive degree of power. Similarly, the wavelength and power of the laser generator are selected to avoid eye injuries from scattering of the electromagnetic beam  140  while, at the same time, providing a wavelength with efficient atmospheric penetration. Selection of the wavelength also should be made with respect to the photocells used in the electromagnetic energy receiver  130  so that the electromagnetic beam  140  will provide energy at a wavelength that can be efficiently converted by the photocells. Similarly, the photocells suitably are chosen for efficiency at a laser wavelength having good atmospheric penetration while reducing potential eye injury. 
     In one presently preferred embodiment, the laser generator is operable to generate a 1.064 μm-wavelength Nd:YAG laser. Other commercially-available compact, single mode high power lasers in the 100-300 W range are available in the 1.07 μm range, along with solar cells that operate at a high efficiency at this wavelength range. A laser at this frequency emits sufficient energy to provide a convertible energy source for the device  100 . A laser operating at this wavelength has a transmission coefficient of about 70% at 1 km. Beam quality is also a consideration because, in one presently preferred embodiment, the electromagnetic beam not only serves as a power source but also as communications conduit and vehicle control system. A 1.064 μm wavelength represents a compromise between concerns of power output, conversion efficiency, atmospheric transmission, eye-safety, and beam quality. 
     A suitable atmospheric window exists at the 1.06-1.07 μm wavelength because the laser beam can penetrate earth&#39;s atmosphere with minimum attenuation. In one presently preferred embodiment, an estimated power budget for the device  100  is in the range of 8-10 watts. Therefore, the device can collect sufficient power from a 50-100 W watt laser at a distance of 1 to 2 km. 
     In one presently preferred embodiment, the beam generated by the beam generator  210  is expanded to minimize spread perpendicular to an axis of projection of the beam over a proposed range of operation. Minimizing spread is desirable to prevent wasted scattering of the energy projected by the beam generator  210  so as not to waste power as well as to allow the positioning control system (not shown) to be able to project a constant amount of power along the length of its virtual tether and also measure the length of the tether. An electromagnetic beam of roughly 10-15 cm in diameter is considered suitable. Using a 50 W laser, when the beam is expanded over a 10 cm circle, the incident power is 0.6 W/cm 2 . A 10 cm diameter beam does not have substantially any beam divergence for a distance of 1-2 kilometers. 
     The electromagnetic energy beam  130  generated by the beam generator  210  also can be modulated to communicate additional control information to the device  100 . If the positioning control system (not shown) is suitably equipped, modulated signals included in the electromagnetic beam  130  can be used to adjust how the device  100  responds to the electromagnetic energy beam  130 . For example, this response can control surveillance devices (not shown) and telemetry, as well as other functions of the device. It will be appreciated that such control also could be transmitted using a separate modulated electromagnetic energy beam or RF signals. 
     Referring now to  FIGS. 3 and 4 , the housing  110  has generally curved sides  310  around most of the perimeter of the device  100 . The curved sides  310  present a smaller drag profile to prevailing cross winds than do generally flat sides. However, in one presently preferred embodiment of the device  100 , the housing includes at least one flat end  320  on which the electromagnetic energy receiver  130  is disposed. Disposing the electromagnetic energy receiver  130  on a flat surface simplifies the balancing of the energy received by the electromagnetic energy receiver  130 .  FIG. 3  also shows an edge of a photocell array  150 . The photocell arrays  150  generally are positioned on an upper surface of the housing  110  of the device to capture sunlight which generally will reach the upper surface of the housing  110 . The photocell arrays  150  are disposed on the housing  110  around and between the rotors  120 . With this arrangement, the photocell arrays  150  make use of otherwise unused, available surface area on the housing  110  without obstructing operation of the rotors  120 . 
       FIG. 5  is another embodiment of the device  500 . The device  500  includes a housing  510  that features rounded sides  520  around an entire perimeter of the housing  510 , a plurality of rotors  120 , and an electromagnetic energy receiver  530  mounted on a face of the housing  510  instead of on a side of the housing  510  as used in the first embodiment of the device  100  ( FIGS. 1-4 ). When the device  500  is powered by an electromagnetic beam  540  projected from substantially below the device  500 , the electromagnetic energy receiver  530  advantageously may be disposed on an lower face of the device  500 . Similarly, when the device  500  is powered by an electromagnetic beam  540  projected from substantially above the device  500 , the electromagnetic beam receiver  530  advantageously may be disposed on an upper face of the device  500 . In either case, when the electromagnetic energy receiver  530  is disposed on a face of the device  500 , the housing  510  of the device  500  advantageously can employ rounded sides  520  around an entire perimeter of the device  500  with aerodynamic benefits such as, for example, reduced drag to crosswinds on all sides. 
       FIG. 6  is a zone diagram of an electromagnetic energy receiver array  600 . As previously described, energy received by the array  600  is used both to generate power for the device and to measure the position of the device. As previously discussed, the device can be programmed to tether itself to a projected position of the electromagnetic energy beam (not shown in  FIG. 6 ) to remain aligned with the beam. It will be appreciated that “the device” suitably refers to the device  100  ( FIGS. 1-4 ) and the device  500  ( FIG. 5 ). To support such alignment, the array  600  suitably is divided into a plurality of angular zones  610  and radial zones  620 . These zones provide carrier collection electrodes (grid) for efficient photoelectric power conversion. Both the angular zones  610  and radial zones  620  are also suitably are used to determine if the beam is moving relative to the array  600  either as the result of the movement of the beam or movement of the device. It will be appreciated that if the array included only angular zones  610 , as position of the array  600  relative to the beam changed along a single angular direction, the array  600  would not indicate the relative movement until the beam moved off the array  600 . Similarly, if the array included only radial zones  620 , as position of the array  600  relative to the beam changed within a single radial zone  620 , the array  600  would not indicate the relative movement until the beam moved off the array  600 . Thus, using an array  600  divided into zones  610  and  620  provides outputs indicating relative movement between the beam and the array  600  so that the device can align itself to the electromagnetic energy beam. 
     In one exemplary embodiment, the electromagnetic energy receiver suitably is formatted into four quadrants,  650 ,  660 ,  670 , and  680 . Employing quadrants  650 - 680  is useful for controlling operation of the device  100 , as will be further explained below. 
       FIG. 7  is a block diagram of a control system  700  used by the device  100  ( FIG. 1 ) and the device  500  ( FIG. 5 ), hereinafter referred to as “the device.” To minimize power consumption and mass, while also providing optimal miniaturization, a control system using low-power application-specific integrated circuits is desirable, although the control system  700  can include off-the shelf components. The control system  700  is configured to generate flight control signals that maintain the device in alignment with the electromagnetic beam. Although a variety of control systems are useable with the device, one presently preferred embodiment of the present invention uses an analog servo loop control system with proportional-integration-differentiation (PID). The loop couples the electromagnetic energy receiver  710  with the motors  720  powering the rotors  120  ( FIGS. 1-4 ). Center locking of the solar cell assembly to the laser beam is achieved when the difference of two cross-quadrant outputs  730  and  740  of the photocell array, for example the difference between quadrant  650  and quadrant  680  and quadrant  660  and quadrant  670  ( FIG. 6 ) in each servo loop approaches zero. When the power of all quadrants is equal, the energy received from the four-quadrant solar cell reaches its maximum level, thereby signifying the device is centered on the electromagnetic beam tether. Accordingly, the control system  700  controls the pitch of the device relative to the ground and the roll of the device around an axis perpendicular to the plane of the electromagnetic energy receiver. 
       FIG. 8  is a yaw control device  800  used by the device  100  ( FIGS. 1-4 ) and  500  ( FIG. 5 ). Along with the control system  700  ( FIG. 7 ) that adjusts the pitch and roll of the device around an axis generally defined by the electromagnetic energy beam  810 , the yaw control device maintains the yaw of the device to keep the electromagnetic energy receiver facing the electromagnetic energy beam. In one presently preferred embodiment, the yaw control device  800  includes an aperture  820  at a center of the electromagnetic energy receiver  830 . Behind the aperture  820  is a channel  840  leading toward a center of the device. At a distal end of the channel  840  opposite the aperture  820  is a segmented photodiode  850 . When the yaw of the device is properly aligned so that the device faces the electromagnetic energy beam  810 , energy from the electromagnetic energy beam  810  falls equally on both detector halves  860 . Any change in the yaw of the device will increase energy received by one detector half  860  at the expense of energy received by the other detector half  860 . The rotors  120  ( FIG. 1 ) can be powered to realign the device to face into the electromagnetic energy beam  810 . On the other hand, a lateral translation of the device can be distinguished from a yaw rotation because a lateral translation will change the energy received by both detector halves  860  equally, thus involving no yaw adjustment. 
       FIG. 9  is a block diagram of a control system  900  used by an embodiment of the present invention. The control system  900  directs flight of the device  100  ( FIGS. 1-4 ) and  500  ( FIG. 5 ) and other supported functions such as control of surveillance devices and telemetry. The control system  900  includes a processor  902  which centrally directs flight and other operations according to preprogrammed instructions and received commands. The processor  902  interacts with the motion control system  904  which controls operation of rotor motors  906  as previously described in connection  FIG. 7 . The processor  902  also interfaces with a vertical reference sensor  908 , inclination sensors  910  and  912 , and a yaw sensor  914  ( FIG. 8 ) to control. Using the sensors  908 - 914 , the processor  902  can interact with the motion control system  904  to maintain the device in level flight at an appropriate altitude and orientation. 
     For controlling flight operations, the processor  902  also interacts with a power management controller  916  that monitors power received by the array  922  of photo cells acting as the electromagnetic beam receiver  130  ( FIG. 1 ) receiving the electromagnetic beam  924  and the solar cells  918  ( FIGS. 1 ,  3 , and  4 ) configured to receive ambient radiation. The power management controller  916  provides input to the processor  902  regarding available power for flight operations. The processor  902  also interacts with a position sensing module  920  which receives position data from the receiver photocells  922  regarding the position of the electromagnetic beam  924  as previously described in connection with  FIGS. 6 ,  7 , and  9 . 
     For responding to commands and controlling other supported functions, the processor also interacts with an RF transceiver  928  and surveillance devices such as a microphone  930 , and a camera  932  operating inside or outside the spectrum of visible light. It will be appreciated that other detection devices, for non-limiting examples including of a chemical sensor, a biological sensor, a radiation detector, and an environmental sensor. Instead of a sensor, the processor  902  also suitably may direct a payload delivery system for transporting a payload object having a size and mass within operational capabilities of the remote-controlled vehicle. 
     In one presently preferred embodiment the transceiver is used as a location beacon which can aid the recovery of the device  100  in the event that the device link with its power source has been permanently severed. The power to this beacon transceiver will be provided by the solar cells on the top surface of the device and or any backup power reserves. The RF transceiver  928  suitably includes a multiple-band transceiver configured receive input and transmit output at the same time. The RF transceiver  928  is configured to transmit telemetry to control stations. The RF transceiver  928  also suitably is configured to transmit data captured by the microphone  930  and the camera  932 . The RF transceiver  928  also is configured to receive commands from control stations to control onboard flight and support operations. For example, RF commands can be transmitted to the RF transceiver to direct the device to land, to enable or disable the microphone  930  and camera, or to indicate other directives. In one presently preferred embodiment, a low-power RF transceiver in the 902-928 MHz or 2.4 GHz frequency range is desirable, similar to the frequency range used in cordless telephones. In addition to or instead of the RF transceiver  928 , the device also can receive commands through modulated laser signals  940  received via an optical interface  942 . The optical interface  942  is coupled with the processor  902  allowing the processor to respond to directives received via the optical interface  940 . 
       FIG. 10  is a diagram illustrating the device  100  tethered by an electromagnetic beam  140  and configured to relay an electromagnetic signal  1000 . The device  100  is flown to a relay point where the device can relay an electromagnetic signal  1000  from a signal source  1010  to a signal destination  1010 . The device  100 , as previously described in connection with  FIG. 2 , receives power and direction from an electromagnetic beam  140  generated by a beam generator  210  associated with a control station  200 . In this case, the control station  200  is a mobile vehicle capable of carrying and powering the beam generator  210 . By directing the electromagnetic beam  140  and/or transmitting RF signals to the device, operators of the control station  200  can control the position of the device  100 . 
     The signal source  1010  is not in a line-of-sight with the signal destination  1020 . However, using the device  100 , the signal  1000  can be redirected or relayed from the signal source  1010  to the signal destination  1020 . The electromagnetic beam  140  can be directed to place the device  100  to a point from which it can redirect or relay the signal. To enable the device  100  to relay the signal  1000 , a reflector  1030 , such as a mirror, is mounted on an underside of the device  100 . In addition to moving the device  100 , the reflector  1030  suitably is mounted on a movable mount (not shown) adjustable by signals from the control station  200  via the electromagnetic beam  140  or RF signals. 
     The electromagnetic signal  1000  suitably is an electromagnetic communications signal, such as a modulated laser signal, generated by a communications transmitter (not shown) and to be received by a communications receiver (not shown). The relay device, instead of a reflector, could be a microwave relay or other communications relay suitable for relaying such a signal. Alternatively, the electromagnetic signal  1000  could be an electromagnetic weapon beam such as a high-powered laser. The electromagnetic weapon beam suitably is generated by a beam weapon (not shown) and directed toward a target (not shown). 
       FIG. 11  is a side-elevational view of an alternative embodiment of the present invention used with a lighter-than-air vehicle  1100 . The device  1100  suitably includes a chamber  1102  such as a balloon, dirigible, blimp or other lighter-than-air device. Methods for generating lift with such devices is accomplished with gases having a lesser density than an ambient atmosphere, by heating ambient air, or by other methods known in the art. Coupled to the chamber are a number of fins  1104  which suitably include control surfaces for steering the device  1100  in pitch or yaw. Also coupled with the chamber  1102  is a control housing  1106 . The control housing  1106  includes control devices suitable to receive and process the electromagnetic beam (not shown in  FIG. 11 ) for controlling operation of the device  1100 . The housing  1106  supports one or more thrust devices  1108 . The thrust devices  1108  can be gimbaled to provide lift and/or thrust. The chamber  1102  provides lift as previously described, thus, the thrust devices  1108  are configured to provide supplemental lift to assist in holding payload aloft and/or for controlling vertical positioning of the device  1100 . In addition, a steering thrust device  1110  may be included in the device  1100  to provide another control mechanism. Coupled to the device  1100  is an electromagnetic beam receiver  1120 . The electromagnetic beam receiver  1120 , as previously described, receives the electromagnetic beam for purposes of at least one of directing a position of the device  1100  and receiving power for operating systems onboard the device  1100 . 
       FIG. 12  is a perspective view of the device  1100  of  FIG. 11  being controlled by an electromagnetic beam  140 . The electromagnetic beam  140  is directed to a location where the device  1100  is desired. As previously described, as the electromagnetic beam  140  is moved, the electromagnetic beam receiver  1120  generates a control signal representative of the position of the electromagnetic beam receiver  1120  is positioned relative to the electromagnetic beam  140 . Responding to the control signal, a positioning system, housed in the housing  1106 , directs the thrust device  1108  and, if included, the steering device  1110  and control surfaces associated with the fins  1104 , to direct the device  1100  to track the location of the electromagnetic beam  140 . By measuring signal strength or other means, the position of the device  1100  relative to the source (not shown) of the electromagnetic beam  140  can be controlled. By modulating and decoding pulses embedded in the electromagnetic signal  140 , by transmitting RF commands, or other means, commands can be given to the device  1100  to further direct its operations. 
       FIG. 13  is a flowchart of a routine  1300  for using an embodiment of the present invention. The routine  1300  begins at a block  1302  with the launch of the device. At a block  1304 , the device receives energy from an electromagnetic energy beam and converts it into electrical power to create lift to fly the device. Once in flight, at a decision block  1306  it is determined if the pitch and roll of the device are correct as described in connection with  FIG. 7 . If the pitch and roll are not correct, at a block  1308  the pitch and roll are adjusted. On the other hand, if the pitch and roll are correct, at a decision block  1310  it is determined if the yaw of the device is correct as described in connection with  FIG. 8 . If the yaw is not correct, at a block  1312  the yaw is adjusted. On the other hand, if the yaw is correct, at a decision block  1314  it is determined if the distance from the source is correct. In one presently preferred embodiment, the distance can be determined by a conventional ranging function by beaming a signal from a control station to the airborne device or vice versa and measuring the delay of the return signal. If the distance is not correct, at a block  1316  the distance is adjusted. 
     It will be appreciated that the principles used for controlling and/or providing power to the remote-controlled vehicle are equally applicable to other than airborne vehicles. To name a few non-limiting examples, the methods for controlling and powering a remote-controlled vehicle are workable with rolling or hovering land-based vehicles, space-based vehicles configured to operate in a partial vacuum, and submersible, floating, or hovering water-based vehicles as well. 
     If at the decision block  1314  the distance is determined to be correct, at a decision block  1318  it is determined if programming changes are being received. Such programming changes suitably include changes in distance from the control station. If it is determined at the decision block  1318  that programming changes are being received, the programming changes are implemented at a block  1320  where operations of the airborne device are adjusted. 
     On the other hand, if it is determined at the decision block  1318  that no programming changes are being received, at a block  1322  the device executes whatever support functions for which the device may be used. The device may be used for surveillance, relaying an electromagnetic signal, delivery of a payload, or another function. 
     At a decision block  1324  it is determined whether flight is to be continued. Flight might be terminated either by a landing signal being received or the airborne device losing its power source supplied by the external electromagnetic beam. If it is determined at the block  1324  that flight is to be continued, the routine  1300  continues at the block  1304  with the receipt and conversion of the energy beam. On the other hand, if it is determined at the block  1324  that the flight is being terminated, the routine  1300  ends at a block  1326  with the landing of the airborne device. It will be appreciated that all of these steps of the routine  1300  can be performed simultaneously or in a different order than shown in  FIG. 13 . 
     While the preferred embodiment of the invention has been illustrated and described, as noted above, many changes can be made without departing from the spirit and scope of the invention. Accordingly, the scope of the invention is not limited by the disclosure of the preferred embodiment. Instead, the invention should be determined entirely by reference to the claims that follow.