Abstract:
A method and system is provided for performing automated air refueling of uninhabited airborne vehicles (UAVs). The method and system includes any combination of a positioning system component, an air collision avoidance system (ACAS) component, a voice processing component, an image processing component, a flight controller, a wireless data link connecting the UAV with the tanker, and refueling components. The ACAS component receives position information of other aircraft, such as UAVs and tankers, over the wireless data link, and generates navigation instructions based on the received position information, and sends the generated navigation instructions to the flight controller. The refueling components include sensors that determine the status of the refueling components. Refueling of the UAV is based on the determined status.

Description:
FIELD OF THE INVENTION 
     This invention relates generally to aircraft refueling and, more specifically, to uninhabited airborne vehicle refueling. 
     BACKGROUND OF THE INVENTION 
     Uninhabited airborne vehicles (UAVs) are becoming widely used by the U.S. Navy and Air Force. Current UAV applications include surveillance, ground attack, and air interdiction. However, further expansion of UAV applications is hindered because, unlike piloted aircraft, they cannot be refueled during flight. Consequently, UAVs cannot perform applications requiring long ranges, such as deep strike interdiction, or long duration surveillance. UAVs also cannot be transported under their own power to remote locations, such as across oceans, because of their range limitations. Instead, UAVs must be flown across oceans in transport aircraft, which is expensive and ties up valuable resources needed for transporting other equipment. Because of these reasons, there exists a need to refuel UAVs in-flight. Because no UAV in-flight refueling system is currently known to exist, there is an unmet need in the art for a UAV in-flight refueling system. 
     SUMMARY OF THE INVENTION 
     The present invention provides automated air refueling (AAR) of uninhabited airborne vehicles (UAVs). According to an embodiment of the invention, a UAV AAR system includes any combination of a positioning system component, an air collision avoidance system (ACAS) component, a voice processing component, an image processing component, a flight controller, a wireless data link, refueling components, and a ground operation station. The voice processing component may be replaced by a wireless voice link to a human operator at the ground operation station using, such as, but not limited to, a satellite communications link. The positioning system component determines the absolute (longitude, latitude, altitude) location of the UAV. A similar system on the tanker determines the absolute position of the tanker, which is transmitted to the UAV over the wireless data link. The absolute position of the UAV and tanker is provided to the flight controller, which determines the relative position (azimuth, elevation, range) of the UAV relative to the tanker, and generates navigation instructions to guide the UAV into the proper position relative to the tanker such that the tanker can connect with the UAV to transfer fuel. The ACAS component also receives the absolute positions of the UAV, as well as the tanker and any other aircraft around the UAV via the wireless data link. The ACAS component also computes the relative position of the UAV relative to the tanker and other aircraft in the vicinity. The ACAS component uses that information to allow the UAV to avoid collisions with the tanker or other aircraft in the vicinity of the UAV. In the event the UAV is headed towards a collision with another aircraft, the ACAS component generates navigation instructions based on the relative position information, and sends the generated navigation instructions to the flight controller to safely fly the UAV away from the collision. 
     The voice processing component receives voice instructions over a voice communications channel, analyzes the received voice instructions, transmits a response according to autonomous analysis, generates navigation instructions according to the analysis, and sends the generated navigation instructions to the flight controller. The voice processing component transmits a response based on the sensed one or more conditions of the refueling components. 
     As an alternative, the voice processing component is replaced by a wireless voice link to a human operator at the ground operation station. For the purposes of simplification, the present invention assumes that voice processing component is used in the refueling operation, although either approach is included in this application. 
     The image processing component includes one or more digital cameras for generating one or more digital images, a memory, and an image processor. The image processor compares the generated one or more digital images to one or more comparable images stored in the image processing component&#39;s memory to determine the position of the UAV relative to the tanker. The relative position information is sent to the flight controller, which compares the relative position information with that generated from the data sent by the positioning system. If the two relative position calculations are consistent, the flight controller generates navigation instructions to guide the UAV into position for refueling. 
     Should either the image processing component or the positioning component fail during the refueling operation, the refueling can be completed using other components. When both components are operational, they provide a safety check against errors or failures in either system. Embodiments of this invention using only one of these components are covered in this invention. 
    
    
     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 illustrates the components of an automatic air refueling system for uninhabited airborne vehicle (UAV) formed in accordance with the present invention; 
     FIG. 2 illustrates processing components included within a processor of the UAV; and 
     FIGS. 3A-C illustrate a flow diagram of an air refueling operation for a UAV of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 illustrates a system  20  for performing automatic air refueling evolutions for uninhabited air vehicles (UAV)  32 , such as, without limitation, US Navy and Air Force UAVs. The system  20  includes one or more refueling aircraft (tanker)  30 , one or more UAVs  32 , and one or more ground operation stations  34 . The tanker  30  includes a navigation system  42 , a positioning system  42   a  such as without limitation a global positioning system (GPS), a wireless data communication component  42   b , and a fueling system  36  with a boom  38 . The fueling system  36  includes components for allowing a boom operator to control the boom  38  during aircraft fueling operations and to send voice commands to a UAV  32  via radio communication (alternatively to the ground operation station operator). The positioning system  42   a  provides the absolute location of the tanker  30  to the UAV  32  via the wireless data communication component  42   b . The wireless data communication component  42   b  allows the tanker to send and receive information to and from UAVs  32 . 
     Each UAV  32  includes a processor  52 , one or more digital cameras  56 , a positioning system  58 , such as without limitation a global positioning system (GPS), refueling sensors and controls  60 , a suitable memory component  62 , a wireless data communication component  55  that communicates (wireless data link) with the wireless data communication component  42   b  of the tanker  30 , and flight controls  64 . The ground operation station  34  includes voice and data communication components (not shown) for allowing communication with the tanker  30  and the UAVs  32 . 
     FIG. 2 illustrates some of the processing components included within the processor  52  of a UAV  32 . The processor  52  includes a voice processing component  80 , an image-processing component  88 , and an air collision avoidance system (ACAS) component  94 . The voice processing component  80  performs voice recognition processing of voice signals received from the tanker  30  or the ground operation station  34 , and sends any necessary voice replies to the tanker  30  or the ground operation station  34 . A non-limiting example of the voice processing component  80  is the ability of the UAV to understand and act upon voice commands from the tanker operator, such as “Breakaway, Breakaway”. Inherent in the invention is synergistic uses of these components such as using the ACAS component to protect the UAV from acting upon unsafe voice commands from the tanker operator. The voice processor component  80  can be located on the tanker  30 . 
     The image processing component  88  analyzes digital images generated by the one or more digital cameras  56  to determine aircraft position relative to the tanker  30 . The UAV  32  receives from the tanker  30  a tanker identification code using the data communication component  55 . The imaging processing component  88  suitably compares the digital images received from the digital camera  56  with digital images of the tanker type aircraft that are retrieved from memory (not shown) based on the received tanker identification code. The imaging processing component  88  determines where the UAV  32  is relative to the tanker  30  (range, azimuth, and elevation). The processor  52  also determines the closure rate of the UAV with the tanker. The processor  52  provides the relative position information to the flight controls  64 , which produces flight commands based on position the UAV  32  at a necessary optimum position relative to the tanker  30  for refueling. A non-limiting example of the image processing component  88  determines that the UAV is located too far to one side and too far below the desired position for refueling relative to the tanker. The image processing component  88  can also process information from lights on the bottom of the tanker used to communicate with pilots of the receiving aircraft. These lights are currently used to affect in-flight refuelings in the event that no electronic emission is permitted from the tanker due to security considerations. 
     The ACAS component  94  receives absolute position information from one or more nearby UAVs  32  or piloted aircraft (not shown) over a wireless data link between the communication components  42   b  and  55 , and generates signals for the flight controls  64  that keep the UAV  32  from colliding with other nearby UAVs  32  or with the tanker  30 . A non-limiting example of an ACAS component  94  determines that the UAV  32  has too great a closure rate with the tanker  30 , and is at risk of an incipient collision with the tanker  30 , such that the ACAS component  94  must send steering commands to the flight controls  64  to maneuver the UAV  32  away from the tanker  30 . 
     FIGS. 3A-C illustrate an exemplary process performed by the system  20  shown in FIGS. 1 and 2. First, at block  102 , a mission is planned and developed. The planned mission includes one or more rendezvous points for refueling of UAV  32 . At a block  104 , the rendezvous points of the planned mission are stored in the memory component  62  in each of the participating UAVs  32 . At a block  108 , the mission begins. At a block  110 , at about the rendezvous time, the UAV  32  moves into a holding position relative to the tanker  30 . Approximately 500 feet aft of the tanker and approximately 100 feet below the tanker is a non-limiting example of a holding position. 
     During the rendezvous, and throughout the refueling operation, at a block  114 , the ACAS component  94  of each of the UAV  32  provides flight control signals for preventing collision with any other UAV  32  at the holding position, or with the tanker  30 . At a block  116 , a UAV  32  that is in the holding position is selected for refueling. The selection of UAV  32  can be performed by an operator at the ground operation station  34 , or an operator on the tanker  30 . In an alternate embodiment, the UAVs  32  exchange information about each of their fuel levels over the wireless data link. The UAVs  32  automatically determine which UAV  32  needs to be refueled first according to the lowest amount of fuel, or other considerations as determined from the information exchanged over the data link. At a block  120 , the selected UAV  32  closes to a refueling set-up position using flight control (navigation) information determined using the positioning system  42   a  information of the tanker  30  and the positioning system  58  information of the UAV  32 , or flight control information provided by the image processing component  88 , or the voice processing component  80 . 
     As shown in FIG. 3B, at a block  122 , the boom operator (boomer) authorizes the UAV  32  that is in the refueling set-up position to close to a refueling position. The boomer suitably performs this authorization by providing a verbal command or digital command sent over the wireless data link to the UAV  32  or as an alternative, through voice contact with the ground station operator  34 . “Clear to contact position”, or an equivalent digital message, is a suitable command provided by the boomer. At a block  126 , the UAV  32  processes the verbal command at the voice processing component  80 , or at the processor  52  for a digital command, and sends a reply command, such as “Roger, cleared,” or its digital equivalent, to the tanker  30 . At a block  130 , the UAV  32  navigates into the refueling envelope using flight control information suitably provided by the image processing component  88  that is backed up or checked by an analysis of tanker and UAV  32  position information. At block  132 , the UAV  32  processes any further verbal commands sent by the boomer as necessary. The following is a non-limiting example of verbal commands provided by the boomer: 
     “Forward X” 
     “Up X” 
     “Back X” 
     “Down X” 
     “Left X” 
     “Right X” 
     where X=a distance value 
     The UAV  32  sends a repeat of the command back to the boomer/tanker. At a block  136 , when the boomer determines that the UAV  32  is in the proper position for refueling, the boomer provides a verbal query asking if the UAV  32  is ready to receive fuel. At a block  138 , the UAV  32  receives the query from the boomer, prepares the refueling controls  60 , and sends a ready response when the UAV  32  is properly configured to receive fuel. 
     As shown in FIG. 3C, at a block  142 , the boomer inserts the boom into the refueling port of the UAV  32 . At a block  144 , the boomer verbally or digitally requests the UAV  32  to confirm contact with the boom. At a block  148 , in response to the boomer&#39;s query request to confirm contact, the UAV  32  checks the refueling sensors to determine if proper contact is indicated. If proper contact is indicated, a “confirmed contact” response is suitably sent to the boomer. At block  150 , refueling begins. At block  152 , the UAV  32  maintains refueling position according to flight control signals generated by the image processing component  88 . In one embodiment, the image processing component  88  receives digital images from the digital camera  56  of the tanker  30 . The image processing component  88  generates flight control signals in order to maintain the tanker in a geometric format that places in the UAV  32  in the refueling envelope. At block  154 , when refueling is complete, the UAV  32  disengages from the tanker and continues on the planned mission. 
     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.