RELATED APPLICATIONS 
       [0001]    This application claims the right of priority under 35 U.S.C. §119 to patent application no. EP12382181 filed May 17, 2012, in the European Patent Office, the disclosure of which is incorporated herein by reference in its entirety. 
     
    
     BACKGROUND 
       [0002]    This invention relates to a method of extending the operation of an unmanned aerial vehicle (UAV). In other aspects, this invention relates to a UAV, a base station for a UAV and command-and-control device for a UAV. 
         [0003]    UAVs are increasingly being used in civilian applications. Many “blue light” services such as the police services and fire-fighting services now use UAVs for intelligence-gathering operations, such as to provide real-time video images of locations that are difficult or dangerous to attend in person. UAVs are often able to provide such images quickly, conveniently and inexpensively. The UAVs used in such applications are relatively small compared to UAVs used, for example, in military strike operations. These smaller UAVs are often battery powered. This has the advantage of reducing complexity and cost. An example of such a UAV is the AR.Drone offered by Parrot. 
         [0004]    A problem that exists with such smaller UAVs is that their operational duration is limited by their batteries. It is typical for such UAVs to be able to fly for no longer than 15 to 20 minutes before the battery becomes depleted. This is the principal limitation on the use of such devices. 
         [0005]    Attempts have been made to improve the performance of batteries and so address this problem. For example, battery lives have been improved, charging times have been reduced and the energy consumption of UAVs has also been reduced. Despite these improvements this problem of limited endurance persists. 
         [0006]    There therefore remains a need to address this problem. 
       SUMMARY 
       [0007]    Embodiments of the present invention take a different approach from that taken previously. Rather than look at improving batteries, charging times or the power consumption of UAVs, the present approach is to provide an arrangement for the rapid replacement of batteries, or other energy storage devices, on UAVs such that effective operational duration can be extended. 
         [0008]    According to a first aspect of this invention, there is provided a method of extending the operation of an unmanned aerial vehicle (UAV), the method comprising the steps of detecting that an energy storage device on board the UAV is depleted below a threshold level, landing the UAV at a base station, and initiating operation of a base station to cause a replacement mechanism thereof to remove the storage device on board the UAV from the UAV and to replace this with another storage device. 
         [0009]    The method may further comprise the step of operating the base station to detect the position of the UAV relative to the base station when landed. This may include operating sensors at the base station to sense the position of the UAV. Sensing the position may include sensing the orientation of the UAV. Sensing the position may comprise operating pressure sensors positioned in and/or on a landing surface of the base station and/or optical sensors positioned in and/or on and/or around that surface. The surface may be a launch and recovery pad. Sensing the position may comprise generating information indicative of the position and/or orientation of the UAV. 
         [0010]    The operation of the base station may comprise the replacement mechanism operating to take the other storage device from a store thereof. The operation of the base station may comprise operating the replacement mechanism using the detected position and/or orientation of the UAV to move replacement structure of the replacement mechanism to the UAV to remove the storage device therefrom. The operation of the base station may comprise operating the replacement mechanism using the information indicative of the sensed position and/or orientation of the UAV to move the replacement structure of the replacement mechanism to the UAV to couple the other storage device thereto. These steps may occur in the sequence in with they are recited herein; they may occur in another sequence. 
         [0011]    The other storage device may not be depleted below the threshold. The store may be a charging station at which storage devices are replenished with energy such that their store thereof is above the threshold and such that the store of energy therein is substantially at a maximum. Each storage device may be a battery, a super capacitor, and/or a container of fuel. 
         [0012]    The method may be carried out as a result of instructions executed by a processor on the UAV and/or a processor at the base station and/or a processor at a remote command-and-control device. 
         [0013]    According to a second aspect of this invention, there is provided a UAV, the UAV arranged to carry out one, more or all of the steps of the method of the first aspect. 
         [0014]    According to a third aspect of this invention, there is provided a command-and-control device arranged to carry out one, more or all of the steps of the method of the first aspect. The command-and-control device may comprise computer processing means. For example, it may comprise a computer such as a portable computer. Non exhaustive examples of a portable computer comprise a laptop, a tablet PC and a smartphone. 
         [0015]    According to a fourth aspect of this invention, there is provided a base station arranged to carry out one, more of all of the steps of the method of the first aspect. The base station may be arranged as defined hereinabove. 
         [0016]    The base station may comprise the replacement mechanism at the base station to remove the storage device on board the UAV from the UAV and replace this with another storage device. The base station may comprise the sensors to sense the position of the UAV. The replacement mechanism may comprise the replacement structure to remove the storage device from the UAV. The replacement mechanism may comprise a robot arm arranged to remove and/or fit storage device to and/or from the UAV. The base station may comprise the store of energy storage devices. The base station may comprise the landing surface. 
         [0017]    Features of the first aspect may also be features of each other aspect. 
         [0018]    Operation of the UAV may be controlled as a result of instructions executed by a processor on the UAV and/or a processor at the remote command-and-control device. Operation of the base station may be controlled by a processor at the base station and/or by a processor at the UAV and/or by a processor at the remote command-and-control device. 
         [0019]    One, more or all steps may happen automatically subsequent to it being detected that the energy storage device on board the UAV is depleted below a threshold level 
         [0020]    According to a fifth aspect of this invention, there is provided a record carrier comprising processor-executable instructions to cause a processor to carry out a method according to the first aspect. 
         [0021]    The record carrier may comprise solid state storage means, such as, for example, a ROM, EPROM and/or EEPROM. The record carrier may comprise optical and/or magnetic storage means, such as, for example, a CD-ROM, DVD-ROM and/or magnetic storage disk. The record carrier may comprise a signal such as an electrical, optical and/or wireless signal. 
         [0022]    Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0023]    Examples of methods and systems in accordance with the teachings of the present disclosure are described in detail below with reference to the following drawings. 
           [0024]      FIG. 1  shows in schematic form a UAV, a base station and a command-and-control station. 
           [0025]      FIG. 2  shows a flowchart illustrating the method of operation of the command-and-control station shown in  FIG. 1 . 
           [0026]      FIG. 3  shows a flowchart illustrating the method of operation of the base station shown in  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION 
       [0027]      FIG. 1  shows in schematic form an overview of a UAV  100 , a base station  200  that includes a charging station  300 , and a command-and-control (C2) station  400 . 
         [0028]    In this embodiment, the UAV  100  is an existing UAV, such as the AR.Drone provided by Parrot. It is a battery-powered quad-rotor UAV that is able to communicate wirelessly with the C2 station  400 . The wireless communication is such that the UAV can receive commands from the C2 station  400  that control operation of the UAV  100 , and can send information about operation of the UAV  100  to the C2 station  400 . The UAV  100  has an energy storage device in the form of a removable and rechargeable battery  110 . 
         [0029]    The C2 station  400  is, in this embodiment, a laptop that communicates wirelessly with the UAV  100  using a radio. The C2 station  400  communicates using WiFi. In other embodiments, other forms of wireless communication are envisaged. 
         [0030]    The base station  200  takes the form of a launch and recovery pad  210  on which the UAV  100  can land and from which it can take off. The pad  210  is arranged with sensors (not shown) to sense the position and orientation of the UAV  100  when the UAV  100  is on the pad  210 . In this embodiment, this is done by the provision of pressure sensors embedded within the pad  210  that are responsive to the weight of the UAV  100  to produce a signal indicative of the position of the UAV  210  on the pad. Optical sensors are also provided on and around the pad  210  to provide a signal indicative of the position and orientation of the UAV  100  when positioned on the pad  210 . Signals produced by the sensors are fed to a control unit (not shown) of the base station  200 . The control unit includes a microprocessor and a record of software executable by the microprocessor to cause it to operate the base station  200  in the manner described herein. The control unit is operable to ascertain, from the signals produced by the sensors, the position and orientation of the UAV  100  on the pad  210 . 
         [0031]    Also forming part of the base station  200  is a robot arm  220 . The robot arm  220  is arranged to access the UAV  100  wherever the UAV  100  is positioned on the pad  210 . In this embodiment, this is accomplished by the robot arm  220  having wheels  230  that allow the robot arm, under the control of the control unit, to move over the pad  210 . Movement of the robot arm  220  is further provided for by it being articulated such that sections of the arm  220  are pivotable relative to other sections of the arm  220 . One such pivot is shown at  222 . A battery replacement section  223  of the arm  220  is provided with two battery engagement portions  224 . Each portion is provided with selectively operable magnetic contacts that are operable to releasably engage a battery when adjacent to a battery, such that the battery is grasped by the engagement portion  224  for lifting, moving and subsequently releasing. In other embodiments, other forms of engagement, such as a pincer arrangement, are envisaged. The battery-replacement section  223  is pivotally mounted adjacent its centre to the remainder of the robot arm  220  such that the relative positions of each of the two engagement portions  224  can be swapped by rotating the replacement section  223  180 degrees about its pivot. The purpose of this will become clear. 
         [0032]    Again, operation of the robot arm  220 , including the battery-replacement section  223  and the engagement portions  224  is under the control of the control unit of the base station  200 . 
         [0033]    The charging station  300  forms part of the base station  200 . The purpose of the charging station  300  is to hold batteries for charging and to receive depleted batteries from, and make recharged batteries available to, the robot arm  20 . Accordingly, the charging station  300  is arranged to hold multiple batteries (in this embodiment five are envisaged) and to charge each one from a depleted state to a state of maximum charge. The charging station is positioned within reach of the robot arm  220  such that the robot arm  220  can deposit for charging at the charging station  300  a depleted battery that has been removed from the UAV  100  and can collect from the charging station  300  a recharged battery for fitting to the UAV  100 . The charging station  300  also operates under the control of the control unit of the base station  200 . 
         [0034]    The control unit of the base station  200  also has a wireless communication unit to communicate wirelessly, again in this embodiment by using WiFi, with the C2 station  400 . 
         [0035]    The C2 station  400  takes the form of, in this embodiment, a laptop computer. The computer is able to communicate wirelessly, in the manner previously described, with each of the control unit of the base station  200  and the UAV  100 . The C2 station  400  runs software that controls operation of both the UAV  100  and the base station  200 . In other embodiments, however, it is envisaged that the base station  200  may control its own operation in response to the software running thereon and in response to signals from the UAV  100  and/or detecting that the UAV  100  has landed on the pad  210 . 
         [0036]    Operation of the various components will now be described with reference to the flowchart of  FIG. 2 . 
         [0037]      FIG. 2  shows the method of operation  500  of the C2 station  400 . This method  500  is a subroutine that is executed during normal operation of the UAV  10  under the control of the C2 station  400  when the C2 station detects at a first step  510  that the battery  110  of the UAV is discharged below a threshold value such that it is determined that the battery  110  should be replaced. 
         [0038]    Upon determining at step  510  that the battery  110  should be replaced, the method  500  proceeds to step  520  at which the C2 station  400  sends a signal to the base station  200  that the robot arm  220  should retrieve a fully charged battery  120  from the charging station  300 . The method  500  being run by the C2 station then proceeds to step  530  at which the C2 station  400  controls the UAV  100  to land on the launch and recovery pad  210  of the base station  200 . 
         [0039]    The method  500  being run by the C2 station  400  then waits at step  540  for a signal from the base station  200  that the UAV  100  has been fitted with the new battery  120  and is ready for takeoff. 
         [0040]    In the meantime, the method  600  runs on the base station  200 . This is in the form of software being executed by the control unit of the base station  200  and is shown in  FIG. 3 . The method  600  is initiated at a first step  610  when the base station  200  receives the signal from the C2 station  400  that the robot arm  220  should retrieve the fully charged battery  110  from the charging station  300 . 
         [0041]    Upon receiving this signal, the method  600  running on the base station  200  proceeds to step  620  at which the control unit of the base station  200  controls the robot arm to move to the charging station  300 . When the robot arm is at the charging station  300 , the magnetic contacts of the engagement portion  224  that is currently positioned at the end of the robot arm  220  are operated to pick up the fully charged battery  120 . The robot arm  220  is then operated to rotate the battery replacement section  223  180 degrees about its pivot such that the other, empty, engagement portion  224  is at the end of the arm  220 . 
         [0042]    The method of the base station  600  then moves on to step  630  at which the base station detects whether or not the UAV  100  has landed on the pad  210 . This is done by sensing the signals from the pressure sensors in the pad  210  and the optical sensors in and around the pad  210 . When it is detected that the UAV  100  has landed on the pad, the signals from the sensors are used at step  640  to determine the position and orientation of the UAV  100  on the pad  210 . 
         [0043]    Once this is done, the robot arm  220  is operated at step  650  to move to the determined position of the UAV  100  and to operate the currently empty engagement portion  224  that is at the end of the arm  220  to energise the magnetic contacts and pick up the discharged battery  110  from the UAV. The battery replacement section  223  of the robot arm  220  is then rotated 180 degrees about its pivot to swap the positions of the discharged battery  110  and the fully charged battery  120 . In this way, the fully charged battery  120  is now positioned adjacent the UAV  100 . The fully charged battery  120  is then dropped into placed in the UAV  100  by de-energising the magnetic contacts of the relevant battery engagement portion  224 . 
         [0044]    The method then proceeds to step  660  at which the robot arm is moved into a position in which it projects outside and away from the pad  210  so as not to obstruct take off of the UAV  100 . Once this is done, the base station  200  sends a signal at step  670  to the C2 station  400  that the batteries  110 ,  120  have been swapped and the UAV  100  is ready to resume operation. 
         [0045]    The method  600  running on the base station  200  then waits at step  680  until it is detected, by way of the sensors, that the UAV has left the pad  210 . Once it has been determined that the UAV has left the pad  210  the robot arm  220  is operated to drop off the discharged battery  110  at the charging station  300  for recharging. The method  600  then returns to step  610  to wait for another signal that it should pick up another fully charged battery. 
         [0046]    Returning now to the method  500  running on the C2 station, that method had been waiting at step  540  for a signal that the UAV&#39;s discharged battery  110  had been swapped for a fully charged battery  120  and is ready to resume operation. As mentioned, this signal is sent from the base station  200  at step  670  of the method running on the base station  200 . Upon receiving this signal, the C2 station  400  proceeds to step  550  at which it controls the UAV  100  to take off for resumed operation. The subroutine then returns to the first step  510  to wait for the new battery  120  to become discharged and run the method again. 
         [0047]    In this way, a discharged battery on the UAV is quickly, conveniently and repeatedly swapped for a fully charged battery, thereby prolonging the effective operating duration of the UAV  100  to be many times its normal operating duration. 
         [0048]    In the foregoing discussion, specific implementations of exemplary processes have been described, however, it should be understood that in alternate implementation, certain acts need not be performed in the order described above. In alternate examples, some acts may be modified, performed in a different order, or may be omitted entirely, depending on the circumstances. Moreover, in various alternate implementations, the acts described may be implemented by a computer, controller, processor, programmable device, firmware, or any other suitable device, and may be based on instructions stored on one or more computer-readable media or otherwise stored or programmed into such devices (e.g. including transmitting computer-readable instructions in real time to such devices). In the context of software, the acts described above may represent computer instructions that, when executed by one or more processors, perform the recited operations. In the event that computer-readable media are used, the computer-readable media can be any available media that can be accessed by a device to implement the instructions stored thereon. 
         [0049]    While various examples have been described, those skilled in the art will recognize modifications or variations which might be made without departing from the present disclosure. The examples illustrate the various aspects of the disclosure and are not intended to limit the present disclosure. Therefore, the description and claims should be interpreted liberally with only such limitation as is necessary in view of the pertinent prior art.
A method of extending the operation of an unmanned aerial vehicle (UAV) is disclosed. The method comprises detecting that an energy storage device on board the UAV is depleted below a threshold level, landing the UAV at a base station, and initiating operation of the base station to cause a replacement mechanism thereof to remove the energy storage device on board the UAV from the UAV and to replace this with another energy storage device.