Drone flight control inside wind turbine tower

Abstract

Aspects of the invention relate to a wind turbine system comprising a tower and a nacelle mounted to the tower having an internal tower space, and a unmanned air vehicle system adapted for inspection activities within the internal tower space. The tower is provided with an elongated guide element extending from a first vertical position in the internal tower space to a second vertical station in the internal tower space, wherein the unmanned air vehicle system includes a connection system configured to couple the unmanned air vehicle system to the elongated guide element so that the unmanned air vehicle system is guided by the elongated guide element as it flies between the first vertical station and the second vertical station within the internal tower space.

Description

[0001] DRONE FLIGHT CONTROL INSIDE WIND TURBINE TOWER

[0002] TECHNICAL FIELD

[0003] This disclosure relates to flight control of an unmanned air vehicle system or drone inside a wind turbine tower. An aspect of the invention relates to a wind turbine system incorporating the system of the invention.

[0004] BACKGROUND

[0005] Wind turbines for power generation are well known in the art. In a common arrangement, a nacelle is mounted on a tower, with a multi-bladed rotor being mounted on the nacelle. The multi-bladed rotor converts the wind energy into rotational kinetic energy that is in turn is converted to electricity by a generator housed inside the nacelle and coupled to the rotor, typically via a gearbox.

[0006] The windy locations in which wind turbines are typically positioned are often harsh and corrosive environments, for example at or near the seas or oceans. As such, they require routine maintenance and inspection to minimise downtime and maintain efficient operation. Typically, the interior of the wind turbine is accessed by technicians so that internal systems and structures can be inspected. From those inspections, appropriate maintenance can be planned and carried out, if required.

[0007] As mentioned above, on-site visual inspection of tower, nacelle, hub, blade and other internal components is a time consuming process which is made more so by increasing wind turbine size, fleet size and design complexity.

[0008] Oftentimes, the first unscheduled visit to a given wind turbine is performed ‘blind’, i.e., with little or no knowledge of the cause of any issue that may be present. Alternatively, repair requirements may be known, but the replacement component derivative is unknown, requiring a visit to the turbine to prepare for the repair / replacement. In another scenario, there may be a delay before a repair is ready and consistent monitoring of the issue is required. In any of these scenarios, significant time and effort is required for technicians to attend the often remotely located wind turbines to address these various tasks.

[0009] The use of drones is becoming increasingly popular with wind turbine maintenance and inspection, particularly for hard to reach external systems and components, such as the blades. In some examples drones are used to take still or video images of the wind turbine structure. Such drones may be controlled remotely or autonomously. However, the control of such systems in the context of wind turbine inspections is challenging.

[0010] It is against this background that the present invention has been devised.

[0011] SUMMARY OF THE INVENTION

[0012] According to an aspect of the present invention there is provided a wind turbine system comprising a tower and a nacelle mounted to the tower, and an unmanned air vehicle system adapted for inspection activities within the wind turbine, wherein the unmanned air vehicle system includes a navigation system configured to be operable in a first navigation mode and a second navigation mode. In the second navigation mode, the unmanned air vehicle system is configured to navigate through an internal space of the wind turbine with greater accuracy compared to when the navigation system is operable in the first navigation mode.

[0013] An advantage of the examples of the invention is that the unmanned air vehicle system may only engage in or operate in the second navigation mode in certain circumstances, or positions within the wind turbine, for example if it is in the necessary internal location to take images of flange bolts. This means that the more accurate second navigation mode does not have to be operable throughout the wind turbine. An advantage of this is that the unmanned air vehicle can travel through the wind turbine more quickly when in the first navigation mode in order to get to the required locations, but then operate in the second navigation mode to carry out measurements. This can be an effective way to conserve power for the unmanned air vehicle system thereby extending run time.

[0014] In the first navigation mode the navigation system may activate a first navigation subsystem having a first predetermined navigational accuracy, and, likewise, in the second navigation mode, the navigation system may activate a second navigation subsystem having a second predetermined navigational accuracy, wherein the second predetermined navigational accuracy is greater than the first predetermined navigational accuracy. Therefore, the vehicle system may operate discrete subsystems with different navigation capabilities, the second of which provides for more accurate navigation that the first. In one option, the first navigation subsystem is configured to use a predetermined internal map of the internal space within the wind turbine system to navigate the unmanned air vehicle system. For example the first navigation subsystem may maintain an internal map stored within an on-board memory. The memory may be any suitable rewritable or non-rewritable memory. The map may be preinstalled in the memory of the vehicle system, but it may also be downloaded, for example when the vehicle system visits a wind turbine for the first time. The internal map may also be ‘built’ during an initial exploration phase of the vehicle system as part of a SLAM initialisation process where the map is created using appropriate simultaneous location and mapping algorithms.

[0015] In contrast to the first navigation mode in which the vehicle system may navigate the internal space using a stored map in conjunction with suitable beacons, markers, visual indicia or otherwise, in the in the second navigation mode, the second navigation subsystem may be configured to use a scanning-type direction and ranging device to navigate the unmanned air vehicle system. Suitably, such a device may be a LiDAR system, which would be understood by a skilled person.

[0016] In the first navigation mode, the first navigation subsystem may be configured to locate the unmanned air vehicle system within the internal map using localised position system within the wind turbine system. For example, this may be achieved by means of an ‘indoor GPS’ type system which are available commercially and as would be understood by a skilled person.

[0017] Switching between the first navigation mode and the second navigation mode may be controlled on the basis of when the vehicle system senses it is at or near one or more predetermined locations within the internal space within the wind turbine system. This can be useful since the system can switch to the ‘accurate’ navigation mode when it is at or approaching a location at which measurements need to be made. As such the one or more predetermined locations may be provided by at least one of: corresponding waypoints in an internal map of the internal space stored in memory; one or more visual fiducial markers; one or more non-visual fiducial markers.

[0018] In the second navigation mode, the unmanned air vehicle system may be configured to carry out an inspection task within the internal space of the wind turbine system. As an enhancement to the operation of the vehicle system, in either navigation mode, it may be configured to: receive data indicative of the swaying movement of the tower; control the flight path of the unmanned air vehicle system to compensate of the swaying movement of the tower. This may be beneficial because the tower can sway significantly during operation and so taking account of this movement during operation of the vehicle system can guard against striking internal surfaces within the tower. The swaying of the tower is generally greater at increased vertical levels, so the system may be responsible to altitude to take account of greater swaying oscillations at increased vertical elevations. The system may be configured to cause the vehicle system to fly in synchrony with the vertical oscillations, but in alternative approaches the system may be configured to maintain an increased clearance from internal surfaces in dependence on the amount of tower sway.

[0019] In another enhancement, the navigation system may be configured to operate also in a third navigation mode, which may be activated when the unmanned air vehicle system moves from the internal space of the wind turbine system to an environment external to the wind turbine system. For example, the third navigation mode may activate a global navigation satellite system to navigate the unmanned air vehicle system.

[0020] In another aspect, examples of the invention may provide a wind turbine system comprising a tower and a nacelle mounted to the tower, and a unmanned air vehicle system adapted for inspection activities within the wind turbine system, and further comprising computing means configured to determine tower movement data indicative of the swaying movement of the tower, and control the flight path of the unmanned air vehicle system to compensate of the swaying movement of the tower.

[0021] For the avoidance of doubt, the computing means may comprise any suitable combination of process, input / output system, memory, user interface and so on in order for the vehicle system to operate in accordance with the desired functionality. Further details of the computing means are provided later in this discussion, by way of example only.

[0022] As an example, the computing means may comprise a vehicle controller onboard the unmanned air vehicle system, wherein the vehicle controller is configured to control the flight path of the unmanned air vehicle system based on the determined tower movement data. The computing means may further comprise a wind turbine controller configured to determine the tower movement data and to transmit the determined tower data to the vehicle controller.

[0023] In one example, the vehicle controller, in controlling the flight path of the unmanned air vehicle system, may adjust a control signal so that the flight path is adjusted in phase with the movement of the tower. In another approach, the vehicle controller may adjust a control signal so that the flight path is adjusted to increase a clearance distance between the unmanned air vehicle system and interior surfaces of the tower.

[0024] The computing means may further be configured to: determine when swaying movement of the tower exceeds a predetermined threshold and, in response, control the flight path of the unmanned air vehicle system to land in a predetermined safe zone. The predetermined safe zone may include a docking station for the unmanned air vehicle system located inside the wind turbine tower.

[0025] In another aspect, examples of the invention provide a wind turbine system comprising a tower and a nacelle mounted to the tower having an internal tower space, and a unmanned air vehicle system adapted for inspection activities within the internal tower space. The tower is provided with an elongated guide element extending from a first vertical position in the internal tower space to a second vertical station in the internal tower space, wherein the unmanned air vehicle system includes a connection system configured to couple the unmanned air vehicle system to the elongated guide element so that the unmanned air vehicle system is guided by the elongated guide element as it flies between the first vertical station and the second vertical station within the internal tower space.

[0026] An advantage of the invention is that the guide element may provide constrained flight whilst the unmanned air vehicle moves up or down through the wind turbine tower. This may reduce computing burden and therefore also power requirements and therefore provide a more energy efficient system with improved run time. Another advantage is that a constrained flight path may provide a safer journey for the air vehicle as it moves from one working location to another.

[0027] In one example, the connection system may be configured to restrain the unmanned air vehicle system at a fixed separation distance from the elongated guide element. In an alternative approach, the connection system may be configured to allow controlled movement of the unmanned air vehicle system towards and away from the elongated guide element. For example, this may be achieved by way of a deployable tether system or comparable implementation.

[0028] The connection system may be configured to permit the unmanned air vehicle system to be coupled and decoupled from the elongated guide element. Therefore, the unmanned air vehicle system can couple itself to the guide element for flight through the internal space from one working location to another, and then decouple from the guide element when it arrives at its destination so it can fly around and perform an appropriate maintenance action like a series of measurements or imaging of flange connections.

[0029] The system may further include a docking station configured to dock with the unmanned air vehicle system, wherein the docking station is located at the first vertical station. The vehicle system can therefore remained coupled to the guide element when at the docking station and fly vertically upwards from the docking station, remaining attached to the guide element, when it is energised into operation.

[0030] In one example, the docking station may be provided at a passenger lift platform of the internal tower space. In this example, therefore, the vertical movement of the vehicle system through the internal space may be achieved with the lift platform, which may reduce the required flight time of the vehicle system thereby conserving energy. The elongated guide element may be attached at the first vertical station to a passenger lift platform of the internal tower space.

[0031] In some examples, the elongated guide element has a single function, specifically for guiding the flightpath of the unmanned air vehicle system. In other examples, the elongated guide element may also provide an alternative function, and, as such, may comprise a current-carrying cable and / or a data-carrying cable.

[0032] In another aspect, the examples of the invention provide a wind turbine system comprising a tower and a nacelle mounted to the tower having an internal tower space, and a unmanned air vehicle system adapted for inspection activities within the internal tower space. The tower is provided with a passenger lift system including a passenger lift platform adapted to be raised and lowered within the internal tower space. The wind turbine system further includes a docking station configured to dock with the unmanned air vehicle system. The docking station is located on the passenger lift platform. Usefully, the docking station is conveyed vertically through the internal space of the tower on the lift platform which provides the potential to save energy since the docking station conveys the unmanned air vehicle system to different vertical stations within the tower, whereupon the unmanned air vehicle system may disengage from the docking station at a predetermined vertical station and perform an inspection activity.

[0033] The docking station may be provided with a charging system configured to charge the unmanned air vehicle system when in a docked configuration, and also may be further provided with one or more of: a communication system configured to communicate with the unmanned air vehicle system; a positional beacon configured to broadcast the three-dimensional position of the docking station within the internal tower space.

[0034] In other examples, there may be provided an elongated guide element extending from the docking station to a vertical station in the internal tower space, wherein the unmanned air vehicle system includes a connection system configured to couple the unmanned air vehicle system to the elongated guide element so that the unmanned air vehicle system is guided by the elongated guide element so it flies between the docking station and the vertical station within the internal tower space.

[0035] Preferred and / or optional features of the previous aspects of the invention may be combined with this aspect of the invention as appropriate.

[0036] Within the scope of this application, it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and / or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and / or features of any embodiment can be combined in any way and / or combination, unless such features are incompatible. The applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to amend any originally filed claim to depend from and / or incorporate any feature of any other claim although not originally claimed in that manner.

[0037] BRIEF DESCRIPTION OF THE DRAWINGS

[0038] One or more embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 shows a front view of a wind turbine system to which the examples of the invention may apply;

[0039] Figure 2 is a schematic diagram showing an interior side view of the wind turbine system of Figure 1 featuring an exemplary unmanned vehicle system, such as a drone, for use in the examples of the invention;

[0040] Figure 3 is a schematic diagram of internal systems of a drone for use in the wind turbine system of Figures 1 and 2;

[0041] Figures 4 and 5 are state diagrams of operational methods / processes associated with the drone;

[0042] Figure 6 is a schematic diagram of a wind turbine telemetry system for use with the wind turbine system of Figures 1 and 2;

[0043] Figure 7 is a schematic diagram of a remote control station used to communicate with the drone of Figure 3 and / or the wind turbine telemetry system of Figure 6;

[0044] Figure 8 is a schematic diagram showing the direction of communication between the drone of Figure 3, the wind turbine telemetry system of Figure 6 and the remote control station of Figure 7;

[0045] Figure 9 is a schematic diagram of a docking station for use with the drone of Figure 3;

[0046] Figure 10 is a schematic diagram showing an alternative view of the docking station shown in Figure 9;

[0047] Figure 11 is a schematic diagram showing an alternative system to aid the drone to ascend / descend the wind turbine of Figures 1 and 2;

[0048] Figure 12 is a schematic diagram of the system shown in Figure 11 in the context of the wind turbine system of Figures 1 and 2; Figure 13 is a schematic diagram showing another alternative system to aid the unmanned vehicle system ascend / descend a wind turbine system of Figures 1 and 2;

[0049] Figure 14 is a schematic diagram of the system shown in Figure 13 in the context of the wind turbine system of Figures 1 and 2.

[0050] DETAILED DESCRIPTION

[0051] Examples of the invention provide a wind turbine system comprising a tower and a nacelle mounted to the tower, and an unmanned air vehicle system, hereinafter referred to as a drone, adapted for internal and external inspection activities of the wind turbine system. The drone includes a navigation system that may be configured to be operable in a first and a second navigation mode. In the second navigation mode, the drone is operable to navigate through an internal space of the wind turbine with greater accuracy compared to when the navigation system is operable in the first navigation mode.

[0052] The examples of the invention provide a novel approach for navigating drones that are tasked with conducting inspection and / or maintenance operations for wind turbines. These drones are configured to fly internally within, and externally to, wind turbine systems. Figure 1 shows an example of a wind turbine system 10 to which the invention applies. The wind turbine system 10 shown is a horizontal axis wind turbine (HAWT) and comprises a nacelle 12 on top of a tower 14. The nacelle 12 houses the mechanical and electrical systems of the wind turbine 10. Protruding from a front of the nacelle 12 is a rotor hub 16 which supports the blades 18 of the wind turbine 12. An interior of the nacelle 12 is accessible from an interior of the tower 14. Likewise, the interior of the rotor hub 16 is accessible from the nacelle 12. The interior of the rotor hub 16 provides access to the interior of the blades 18, which are substantially hollow as is conventional. The tower is accessed through personnel door 20 at the base of the tower 14. The personnel door 20 comprises an access opening that allows access between and interior and an exterior of the wind turbine 10. The access opening is closed by a door panel of corresponding size and shape. The interior of the tower may feature a stairs, ladder or elevator to help personnel ascend to the top of the tower 14 and into the nacelle 12. Although the example shown is a HAWT, this is not intended to be limiting. Instead, the wind turbine system may be a vertical axis wind turbine (VAWT) and / or a multi-rotor wind turbine. Figure 2 illustrates an internal view of a typical architecture of a wind turbine system 10 which may be used in the implementation of the embodiments of the invention. Within the tower 14, there are a number of floors 22, or levels, that are accessible by a ladder 24, stairs 54 or an elevator system 26 also known as a passenger lift system. The number of floors 20 is not important and depends on the type and height of wind turbine system 10. The wind turbine system 10 comprises a drone 100 shown in this figure as landed on a docking station 28. The drone is tasked to fly within or around the wind turbine system 10, for example on a flight path denoted by arrows 30.

[0053] Figure 3 shows an overview of internal system of the drone 100, including: a control system 102, one or more propulsion units 104, a power system 106, a communication system 108, a sensor suite 110, mission planning system 112, a navigation system 114 and a connection system 122. The drone 100 may be operated in conjunction with a remote computer system, hereinafter referred to as the ‘remote control station’ 300, which will be described in more detail later with reference to Figure 5.

[0054] The control system 102 is the main computing unit that controls the movement of the drone 100 by controlling the propulsion units 104 based on inputs from the sensor suite 110 and navigation system 114. The control system 102 may implement remote control movement based on received control inputs from the remote-control station 300, autonomous movement, based on its internal mission planning algorithms, or semi-autonomous movement, in which a blend of on-board mission planning and control station-based direction are used. The main responsibility of the control system 102 is as a lower layer controller which is responsible for positional control, attitude control, and velocity control of the drone 100 based on remote control actions or based on self-generated movement directions. The control system 102 comprises a suitable processing environment having a processor 116 and a memory 118 with associated on-board communications functionality, such as a data bus, so it can communicate with other on-board systems of the drone 100.

[0055] To directly control the movement profile, the control system 102 communicates with the one or more propulsion units 104. Four propulsion units 104 are shown here, as would be consistent with the drone system 100 being having a multiple rotors or propulsion units depending on the type of drone 100. However, more or fewer propulsion units 104 are also appropriate. For example, an autonomous helicopter may have a single propulsion unit 104, but other drones may have six or eight propulsion units 104. The propulsion units 104 may be any suitable units for providing controllable movement for the drone 100 and may be electric motors driving suitable rotor blades. However, the propulsion units 104 may also be gas turbines or internal combustion engines, for example.

[0056] The on-board power system 106 is selected to be suitable for the propulsion units 104. For example, for electric motors the on-board power system 106 may be a battery pack, a fuel cell, or even an external power plug so as to receive electrical power from an external source. Conversely, the on-board power system 106 could be an on-board fuel tank in the event that the propulsion units 104 are gas-turbines or ICEs.

[0057] The communication system 108 provides the means to send and receive data to and from systems that are external to the drone 100. For example, the drone 100 may send or receive telemetry data from the wind turbine telemetry system 200, shown later in Figure 4, or the remote-control station 300, shown later in Figure 5. Additionally, the drone 100 may send positional, attitude and velocity data to other drones 100 operating in the area, either as part of a drone swarm or operated independently. The communication system 108 may receive remote control commands from the remote-control station 300 if the drone 100 is operated in remotely controlled mode. Alternatively, or in addition, it may download mission data from the remote-control station 300, which may include data such as what internal components to inspect and how they should be inspected, e.g. by measurement or imaging. The communication system 108 may also upload inspection data to external systems. The communication system 108 may also permit incoming and outgoing communication with other drones so that movement paths and mission objectives can be coordinated with them to achieve a collective goal. The communication system 108 may direct signals by any means known in the art including, but not limited to, cellular or other phone-based networks, over remote-control radio frequency links, UHF or L-band frequency links, microwave frequency links, audio, optical systems such as infra-red or ultraviolet or other appropriate datalinks, networks, or communication paths.

[0058] The sensor suite 110 is operably connected to the control system 102 and provides appropriate sensor data to assist with the operation of the drone 100. For example, the sensor suite 110 may comprise sensors or navigational subsystems such as proximity detectors, for example detection and ranging systems such as LIDAR, RADAR and / or SONAR, a satellite-based positioning system, including for example differential GPS, RTK-GNSS, PPP-GNSS or any other local positioning system set up for positioning control, optical still and video cameras for both navigation and carrying out inspection and guidance tasks, inertial navigation systems to name a few examples. Typically, such a sensor suite 110 would be adaptable to carry more or fewer sensors as required for a particular task. Note that in this context the GPS unit may receive signals directly from satellites to fix the position of the drone 100, although another option would be to implement a differential GPS system (known in the art) which receives signals from a remote differential GPS beacon in order to provide a higher positional accuracy compared to direct GPS. Note that a GPS unit 120 is shown here as integral with the navigation system 114.

[0059] Mission planning system 112 provides a link to the remote-control station 300 to store missions that have been generated on it and to which the drone 100 follows in use. The mission planning system may include suitable memory storage and algorithms to store, provide and generate on the fly appropriate mission objectives, waypoints, operational envelopes, internal maps of wind turbines and so on.

[0060] Navigation system 114 provides control inputs to the control system 102 based on drone position and proximity data received from the navigational subsystems of the sensor suite 110. The navigation system 114 is configured to be operable in at least two navigation modes; a first navigation mode and a second navigation mode. In the second navigation mode, the drone 100 is operable to navigate through an internal space of the wind turbine system 10 with greater accuracy compared to when the navigation system is operable in the first navigation mode. For example, the second navigational mode may operate by enabling additional navigational subsystems detection and ranging systems such as SONAR, RADAR or LIDAR, increase sampling rate of sensors, or enable optical systems with lights that would not ordinarily be enabled in ‘standard flight’. The lights may operate, for example, in the ultraviolet, infrared or visible spectra along with compatible optical sensors. The navigation system 114 may implement a suitable simultaneous localisation and mapping algorithm / engine that is configured to maintain a map of the internal space within the wind turbine system 10 and a location of the drone 100 within the internal pace. SLAM algorithms are generally known in the art and so will not be discussed in further detail here, for brevity. This may be part of an indoor positioning system and location tracking system, which are sometimes known as ‘indoor GPS’, as would generally be understood by a skilled person.

[0061] Figure 4 shows a flow chart of the drone 100 operating in the first and second navigation modes 128, 130. After initial power on 124, the drone 100 enters the first navigation mode 128 by default. In a parallel activity, there is constant monitoring 126 of chosen parameters to enter the second navigation mode 130 when required. Once the parameters are satisfied, the drone 100 switches from the first navigation mode 128 to the second navigation mode 130. Once in the second navigation mode 130, the monitoring 126 remains active, although the chosen parameters are reprioritised for entry into the first navigation mode 128. Again, once these first navigation mode 128 parameters are satisfied, the drone 100 may switch back to operating in the first navigation mode 128.

[0062] The first navigation mode 128 is a default navigating mode for the drone 100. The first navigation mode 128 represents the most efficient mode of operation for the drone 100 where all but essential navigational subsystems are dormant to reduce energy consumption thereby increasing available flight time per charge. In other words, the first navigation mode 128 operates at least a first navigational subsystem in a first predetermined first navigational accuracy that is lower than a second navigational accuracy of the second navigation mode 130.

[0063] The first navigation mode 128 is operable when risk of collision with obstacles such as walls, floors or equipment is low. The first navigational mode 128 relies on at least one navigational subsystem such as an internal map data of the wind turbine system to determine the location of the drone within or around the wind turbine system 10. The internal map data is optionally used in conjunction with optical sensors capable of reading localised position markers at predetermined locations such as fiducial markers (e.g. these may be QR codes for example) placed throughout the wind turbine system 10. The optical data is then processed to localise the drones position relative to the wind turbine system 10. For example, this process may be incorporated into the simultaneous location and mapping (SLAM) algorithm that is internal to the navigation system 114 as discussed above. Alternatively, the predetermined locations may be identified by one or more nonvisual fiducial markers, for example radio frequency (RF) transponders. In summary, the one or more predetermined locations are provided by at least one of corresponding waypoints in an internal map of the internal space stored in memory or one or more visual or non-visual fiducial markers.

[0064] The second navigation mode 130 is an enhanced navigation mode when compared to the first navigation mode 128. The second navigation mode 130 features a second predetermined navigational accuracy that is greater than a first predetermined navigational accuracy. The navigation system 114 is configured to switch between the first navigation mode 128 and the second navigation mode 130 when it is at or near the one or more predetermined locations within the internal space within the wind turbine 10, for example. The drone 100 relies on basic proximity detection and / or internal map data to ascertain when to switch over to or activate the second navigation mode 130.

[0065] In the second navigation mode 130, the drone 100 is configured to carry out an inspection task within the internal space of the wind turbine 10. The higher accuracy of the second navigational mode allows the drone 100 to fly closer to obstacles and, in particular, features of the wind turbine system 10 requiring inspection or scanning. As an example, the drone 100 may be tasked with photographing, either with still images or video, nuts and bolts of a bolted joint between structural tower section of the wind turbine tower 14. In a second navigation mode 130, the drone 100 can approach each bolt of the bolted joint to capture high quality close-up images. These images can then be communicated to the remote control station 300 for analysis.

[0066] The navigation system 114 may be configured also to operate in a third navigation mode 132. Figure 5 shows a flow chart of the drone 100 operation in first, second and third modes 128, 130, 132. As before, after initial power on 124, the drone 100 enters the first navigation mode 128 by default. In a parallel activity, there is constant monitoring 126 of chosen parameters to enter another navigation mode when required. Once the parameters are satisfied, the drone 100 can be switched from the first navigation mode 128 to either the second navigation mode 130 or the third navigation mode 132. Selection is based on satisfaction of predetermined parameters for each mode. Once the drone 100 is operating in another navigation mode, the monitoring 126 remains active, however, the chosen parameters are reprioritised for entry into either of the remaining navigation modes. Again, once either of these navigation mode parameters are satisfied, the drone 100 may switch to another navigation mode.

[0067] The third navigation mode 132 may be activated when the drone 100 moves from the internal space of the wind turbine system 10 to an environment external to the wind turbine system 10. In the third navigation mode 132, the navigation system 114 may be configured to activate a global navigation satellite system (GNSS) to navigate the drone 100. When outside the wind turbine system, the navigation system 114 may provide control inputs to the movement control system regarding path following based on input from GPS data from the GPS Unit 120. In this mode of operation, the system may be configured to operate within predetermined geofenced zones in order to comply with regulations governing aerial vehicles where the wind turbine is installed. The connection system 122 may be configured to mechanically attach the drone to a mechanical navigation guide system, as discussed in Figures 9 and 10 and the corresponding passage below. Alternatively, the connection system 122 could be used to attach a payload to the drone 100, such as a parts or tools for maintenance operations. Such a payload may be held in a fixed position relative to a main body of the drone 100. To provide flexibility over the type of payload that is carried, the connection system 122 may be configured to releasably attach the payload to the drone 100, such that the payload may be removed or replaced after use.

[0068] It should be appreciated that the above description of a drone 100 system is intended as merely an example of the main components of a remote controlled and / or autonomous vehicle and that other components may also be included in a typical system. In general, it should be noted that drones 100 for use in the embodiments of the invention are known and are able to perform in remote control modes, semi- and fully autonomous modes, and are able to carry out manoeuvres in a coordinated fashion in fixed positional relationship with other drones 100.

[0069] Figure 6 shows an example system schematic of the wind turbine telemetry system 200. In this schematic, it can be seen that the wind turbine telemetry system 200 features a controller 202, a communications module 208, a power supply 210, and a sensor suite 212.

[0070] The controller 202 features a processor 204 and a memory module 206. The controller 202 is operable process data recorded by the sensor suite 210 and received from the communications module 208.

[0071] The communications module 208 is configured to transfer data to and from other internal systems of the wind turbine system, for example access control systems or notification systems. Furthermore, the communications module 208 is configured to communicate with systems external to the wind turbine system 10, for example the remote control system 300 or drones 100 internal to or in the vicinity of the wind turbine system 10.

[0072] The power supply 210 is supplied with mains electrical power supplied from an electrical supply grid. Optionally, the power supply 210 may feature an uninterrupted power supply (UPS) operable to store electrical charge, for example in a battery, for supply to the wind turbine telemetry system 200 in the event of power supply failure or deliberate disconnection of the wind turbine system 10 from the grid.

[0073] The sensor suite 212 of the wind turbine telemetry system 200 features various sensors for recording data related to operation of the wind turbine system 10. For example, the sensor suite may feature accelerometers or inertia measurement units positioned both at the bottom and at the top of the wind turbine tower 14 for detection of wind turbine tower 14 deflection or sway. The sensor suite 212 may also feature temperature and humidity sensors within the wind turbine system 10 for detection of water ingress.

[0074] The wind turbine telemetry system 200 is operable to receive data from the sensor suite 212, process that data using the processor 204 and compare that data to acceptable ranges stored in the memory module 206. If any data is out of a predetermined range, for example, wind turbine tower swaying motion, the wind turbine telemetry system 200 may use the communications module 208 to notify the remote control station 300. In addition, the wind turbine telemetry system 200 may communicate with a drone 100 adapted for inspection activities within the wind turbine system 10 to autonomously commence an inspection of the wind turbine system 10 to gather more information as to why the tower sway may be out of specification.

[0075] Additionally or alternatively, the wind turbine telemetry system 200 is configured to quantify data indicative of the swaying movement of the tower, and issue data and / or instructions to the drone 100 to control the flight path of the drone 100 to compensate for the swaying movement of the tower 14 and mitigate risk of collision. This is particularly useful for when the drone 100 must get close to a wall of the tower for inspection activities, particularly when the sway of the tower is greater than the distance of the drone to the wall of the tower.

[0076] One way in which this objective could be achieved is to adapt a position parameter of the control system 102 that is output from the navigation system 114 to take account of the swaying movement. For example, the control system 102 may determine the tower 14 movement acceleration data and combine that with the drone 100 position command data to provide an adapted position command data that is then used to control the propulsion units 104. In this way, tower displacement and sway timing data is used by the drone controller 102 to synchronise the drone’s movements in phase with the tower 14. In another example, the wind turbine telemetry system 200 may instruct the drone 100 to keep a certain, or an increased, distance from internal surfaces of the wind turbine system 10. In this scenario, the drone controller 102 may be configured to evaluate tower accelerometer data to determine if it exceeds a predetermined threshold that indicates that the tower swaying motion is excessive. When the threshold is exceeded, the drone controller 102 may control the propulsion units 104 to maintain an increased separation distance from the internal surfaces of the wind turbine.

[0077] The drone 100 and / or the wind turbine telemetry system 200 may be further configured to determine when swaying movement of the tower exceeds a predetermined threshold and, in response, control the flight path of the drone to land in a predetermined safe zone.

[0078] In a complimentary aspect, it should be understood that tower swaying motion may be a direct consequence of the prevailing wind speed, and that the magnitude of the sway may also be dependent on the vertical height up the tower. Therefore, in some examples the system may be configured to enable or disable flight of the unmanned air vehicle system in one or more sections of the wind turbine tower internal space (i.e. sections based on height within he tower) in dependence on wind speed.

[0079] The wind turbine telemetry system 200 may operate to communicate with an access control system of the wind turbine system 10 to lock personnel doors 20 of the wind turbine system 10 while the drone 100 is in flight inside. Furthermore, suitable systems may be implemented to check whether any personnel are already inside the wind turbine, for example by querying an electronic access log of the wind turbine which records personnel entries and exits. Furthermore, the internal space of the wind turbine may be ‘sealed off’ on a zoned basis by appropriate control of internal access doors and hatches if necessary to ensure that no personnel are sharing the same space as the UAV in flight. This strategy prevents personnel from entering the potentially hazardous environment of a drone 100 operating in a confined space.

[0080] A notification system may be operable by the wind turbine telemetry system 200. Such a notification system may comprise status indicators such as lights, an intercom or a siren. The notification system would serve to notify personnel in the wind turbine 10 or the surrounding area that the that the drone 100 is operating, or is about to operate, inside the wind turbine system 10. Alternatively, the notification system may notify personnel in the area surrounding the wind turbine system 10 that a drone is about to exit the wind turbine system 10, for example.

[0081] A system schematic of the remote-control station 300 as shown in Figure 7. The remotecontrol station 300 provides a control hub for one or more drones 100 as described above and is suitably equipped with a computing platform 302 having an appropriate processing module 304 and memory storage 306. The computing platform 302 implements a suitable control station software package 308 to provide appropriate control station facilities for controlling and coordinating the drone 100, together with other drones 100 if necessary. For example, the software package 308 may include telemetry feeds, status information updates, first person visual (FPV) feeds, mission planning interfaces and algorithms and so on. A user interface 310 is provided to enable to a user / operator to view data relating to the drone 100 and to input control and parameter data into the remote-control station 300. The user interface 310 may comprise a display screen, audio output, a user input means such as a keyboard, joystick, mouse, on-screen buttons or a combination of these.

[0082] The remote-control station 300 also has a communications system 312 in order to send data to and receive data from the drone 100 or the wind turbine telemetry system 200. The remote-control station 300 could be a remote system that is mounted in a maintenance vehicle, such as a type of ship known as a Service Operations Vessel, for example.

[0083] Figure 8 is a schematic showing the intercommunication between the drone(s) 100, the wind turbine telemetry system 200 and the remote-control station 300. It will be apparent to the reader that the exemplary embodiment is a three-way communication between the drone(s) 100, the access control system(s) 200 and the remote-control station 300, although this is not intended to be limiting. The remote-control station could communicate with the drone(s) 100 and the wind turbine telemetry system(s) 200 independently or the communication may be executed in a daisy chain where the remote-control station 300 communicates with the drone(s) 100 which, in turn, communicate with the wind turbine telemetry system(s) 200. Such an arrangement for bi-directional or tri-directional communication may be particularly advantageous when the tower movement pattern changes rapidly, for example during emergency shutdown of the wind turbine system.

[0084] Communication strategies may include, for example, microchip with communication by RFID, Bluetooth, NFC, Wi-Fi, UWB or other wireless communication formats. Alternatively, the communication may be in an audio or optical format. The remote-control station 300 or the wind turbine telemetry system 200 may communicate with the drone 100.

[0085] The signals transmitted between the drone(s) 100, the wind turbine telemetry system(s) 200 and the remote-control station 300 may be encrypted for cybersecurity reasons, i.e. , to prevent unauthorised access to wind turbines or hacking of the drone(s) 100.

[0086] The remote-control station 300 communicates to the wind turbine telemetry system(s) 200 of the wind turbine(s) 10 set to undergo inspection or maintenance. For example, the remote-control station 300 may communicate with the wind turbine telemetry system(s) with a message to enter a ‘maintenance mode’. The wind turbine telemetry system 200 of a wind turbine 10 will then communicate with the other systems of the wind turbine 10 to enter the maintenance mode.

[0087] An example of action taken for a wind turbine 10 to enter into a maintenance mode may be: ensuring the nacelle 12 yaws head to wind; reducing the rotational speed of the rotor hub 16 to a stop state by pitching the blades 18 to zero degrees and applying a brake to the rotor hub 16; and setting the access control system 200 into a state in which it is ready to receive a communication to grant access to an incoming drone 100. The maintenance mode may also set personnel doors 20 of the wind turbine to lock, to prevent personnel from entering the wind turbine 10 which is about to grant entry to a drone 100. Additionally, if the wind turbine 10 comprises an elevator, i.e., a lift or a hoist, the elevator can either ascend to the top or descend to the bottom of the tower 14 so that the drone 100 can utilise vacant elevator path to ascend the tower 14.

[0088] Once the wind turbine telemetry system 200, and therefore the wind turbine 10, is in the maintenance mode, the wind turbine telemetry system 200 could take into account the position and heading of a drone 100 dispatched for maintenance operations on the wind turbine 10. The wind turbine telemetry system 200 receives signals from either the drone 100 or the remote-control station to open in a timely fashion as the drone 100 approaches to allow the drone 100 access to the wind turbine interior. Likewise, either the drone or the remote-control station 300 may signal the wind turbine telemetry system 200 to close either after the drone 100 has entered the wind turbine interior or after the drone 100 has left the wind turbine 10. Alternatively, a drone 100 may enter the wind turbine 10 whilst it is still operational for interior inspection of the turbine 10. In this case, the wind turbine 10 may continue normal energy production as hazards to personnel health and safety are nil if there are no personnel on site.

[0089] Figures 9 and 10 are schematic drawings that show an embodiment of the docking station 26 as shown previously in Figure 2. In this embodiment, the docking station 26 features a cantilevered shelf or plinth which acts as a landing pad 30 for the drone 100. For clarity, Figure 9 shows a drone 100 landed on the landing pad 30 and Figure 8 does not. The landing pad 30 features four fiducial markers 32 positioned at each corner of the rectangular landing pad as shown in Figure 10. Of course, the shape of the landing pad 30 is not intended to be limiting, the landing pad 30 could be hexagonal, octagonal, or any other polygon or shape such as a circle. In the case of any other shape, the fiducial markers 32 would be equi-spaced about a perimeter of the landing pad 30 to outline its boundary to the optical sensors of the drone 100.

[0090] The docking station 26 is a predetermined safe zone for the drone 100 located inside the wind turbine tower 14. The docking station 26 is configured to charge, refuel, communicate and / or transfer data with the drone 100. More detail on these aspects is provided below.

[0091] Figure 9 shows that the docking station 26 is equipped with a power supply 34 for recharging a drone 100 that has docked on the docking station 26 by landing on the landing pad 30. The docking station 26 is supplied with mains electrical power supplied from the grid. Optionally, the docking station 26 may feature an uninterrupted power supply (UPS) 36 operable to store electrical charge to supply to the drone 100 in the event of power supply failure or deliberate disconnection of the wind turbine system 10 from the grid.

[0092] Power is transferred from the docking station 26 to the docked drone 100 by inductive charging as is known in the art. Figure 10 shows an example of where such an inductive coil 44 may be positioned to provide inductive charging to the drone 100. Alternatively, landing pad 30 may feature conductive pads configured to contact corresponding electrical contacts on a landing gear of the drone 100.

[0093] The docking station 26 is further provided with one or more of a communication system 38 configured to communicate with the drone 100. For instance, the docking station 26 may feature a wireless access point to allow the drone 100 to wirelessly connect to a communications network 40. A positional beacon configured to broadcast the three-dimensional position of the docking station within the internal tower space. This may form part of an indoor GPS installation for example, or use near-field communications technology.

[0094] The docking station 26 could also serve to disarm or maintain the drone 100 in a dormant state while it is docked. The active state of the drone 100 in the docking station 26 is controlled by the wind turbine telemetry system 200 such that the drone 100 is selectively armed or disarmed when personnel are permitted access to the wind turbine system 10 interior.

[0095] The docking station 26 may feature a wind turbine system identifier 42 in the form of a fiducial marker in view of a docked drone 100. For example, this wind turbine system identifier 42 could identify the wind turbine system 10 in which the drone 100 is landed. This is particularly useful when the drone 100 is powered on for the first time or after a reboot so that the drone 100 can identify the wind turbine system 10 in which it is docked. This information could then be used to download the corresponding internal map of the wind turbine system 10. Furthermore, it may assist in a handshake when connecting to the wind turbine telemetry system 200 of the wind turbine system 10 the drone 100 is docked within.

[0096] The docking station 26 could also feature a mirror 46, or a reflective surface positioned in view of an optical sensor of the drone 100 docked at the docking station 26. The purpose of the mirror 46 is for the drone to conduct self-diagnosis or visual pre-flight checks, for example checking rotor function. This self-diagnosis is conducted autonomously using the drone’s reflection in the mirror 46. Alternatively, a technician may remotely access a camera of the drone to gain visibility of the drone’s mechanical systems reflected in the mirror 46.

[0097] The docking station 26 may also incorporate a locking system (not shown), for example which may be operated mechanically or electromechanically, which is configured to secure the drone 100 to the docking station 26. This may be useful in circumstances which the tower is moving or when the docking station 26 is position on a moving platform, as is discussed in more detail below. The discussion that has been provided above explains how the trajectory of the drone 100 may be controlled to guide it around the internal space of the wind turbine system 10. The discussion will now explain further features that may provide enhanced control aspects of the drone 10 in a selectively or optionally tethered mode of operation.

[0098] Accordingly, there is provided a mechanical navigation guide 48 as shown schematically in Figures 11 and 12. In these figures, an elongated guide element 50 extends from a lower portion of the wind turbine tower 14 to an upper portion of the wind turbine tower 14 and / or the nacelle 12. For example, the elongated guide element 50 may extend from the docking station 26 to a vertical station or position in the internal tower space. In this embodiment, the drone 100 may be configured to use the connection system 122 to couple to and subsequently decouple from the elongated guide element 50 by releasably latching to the mechanical navigation guide 48. Therefore, the drone 100 is guided by the elongated guide element 50 as it flies between the docking station 26 and the vertical station within the internal tower space.

[0099] Hatches 52 are provided in the floors 22, sized to allow the drone 100 to pass through whilst coupled to the elongated guide element 50. It should be noted that access hatches 52 may be computer controlled, as is appropriate, and may open automatically upon being approached by a drone 100. Suitable hand shaking protocols may be implemented to cause opening and closing of the hatches 52.

[0100] As the drone 100 is coupled to the elongated guide element 50, the combination of the connection system 122 and the mechanical navigation guide 48 is configured to restrain the drone 100 at a fixed separation distance from the elongated guide element 50. This fixed separation distance allows the drone 100 to pass through the hatch 52 without risk of collision with the floor 22. This is particularly advantageous for the drone 100 travelling inside with wind turbine while the tower is swaying.

[0101] Furthermore, the connection between the drone 100 and the elongated guide element 50 is configured to allow controlled movement of the drone 100 towards and away from the elongated guide element 50, but within confines of the hatches 52. For example, the connection system 122 could include a deployable tether in the form of a coil of line. In this example, the coil of line is long enough to allow relative movement between the drone 100 and the elongated guide element 50, but short enough that the drone 100 remains clear of the floor 22 when passing through the hatches 52. Beneficially, this allows the drone 100 to quickly ascend / descend along a predetermined and clear path with minimal risk of collision. As such, this provides opportunity for the drone 100 to ascend or descend the wind turbine tower 14 at maximum power and / or velocity.

[0102] Once the drone 100 reaches a predetermined location within the internal tower space, the drone 100 can be controlled to decouple from the elongated guide element 50. A predetermined location may be an area of the wind turbine tower 14 that requires inspection, or it may be an area where a docking station 26 is located, for example.

[0103] The elongated guide element 50 need not be a dedicated feature of the wind turbine tower 14, for example, the drone 100 may make use of a preexisting elongated feature such as the lifting cable(s) for the elevator 24 or a part of a ladder, such as a safety bar of a ladder. The elongated guide element 50 may also have another function, for example it could be a data cable or electrical cable which also functions as the guide element.

[0104] As an alternative to coupling to a mechanical navigation guide 48, the connection system 122 of the drone 100 may couple directly to the elongated guide element 50. For example, the drone 100 may be equipped with a robotic arm with a suitable end effector such as a active claw or grip that can selectively hold and release the elongated guide element 50.

[0105] Figures 13 and 14 show another example in which wind turbine system 10 comprises a tower 14 and a nacelle 12 mounted to the tower 14 having an internal tower space, and a drone 100 adapted for inspection activities within the internal tower space. The tower 14 is provided with an elevator system 26 including a passenger lift platform 54 adapted to be raised and lowered within the internal tower space, wherein the wind turbine system 10 further includes a docking station 28 configured to dock with the drone 100. As can be seen, the docking station 28 is located on the passenger lift platform 54. Preferably, the docking station 28 is positioned on a top surface of the passenger lift platform 54, although this is not strictly necessary.

[0106] An advantage of this configuration is that the elevator system 26 is configured to convey the docking station 28 to a predetermined vertical station within the internal tower space, wherein the drone 100 is configured to disengage from the docking station 28 at the predetermined vertical station and perform an inspection activity. The inspection activity may be performed as discussed in detail above. Notably, once the drone 100 has disengaged from the docking station 28 when it is at the predetermined vertical station within the wind turbine, the drone 100 can fly through the internal space based on a pre-calculated trajectory as is discussed above.

[0107] In an alternative approach, the drone 100 may be configured to detach from the docking station 28 but remain attached to a lift cable 134 of the elevator system 26 to travel to another vertical position within the wind turbine. Thereafter, at a suitable and predetermined point, the drone 100 may be controlled to detach from the lift cable 134. In this respect, therefore, the lift cable 134 is equivalent to the elongated guide element 50 as described in the previous example.

[0108] As discussed above, the docking station 28 of Figures 13 and 14 may incorporate various computing functionality as implemented by the telemetry system 200 and the remotecontrol station 300 as described herein. Therefore, features of the previous examples of the invention may apply also to this example of the invention.

[0109] It will be appreciated that various changes and modifications can be made to the present invention without departing from the scope of the present application.

Claims

CLAIMS1. A wind turbine system (10) comprising a tower (14) and a nacelle (12) mounted to the tower (14) having an internal tower space, and a unmanned air vehicle system (100) adapted for inspection activities within the internal tower space,wherein the tower (14) is provided with an elongated guide element (50) extending from a first vertical position in the internal tower space to a second vertical station in the internal tower space,wherein the unmanned air vehicle system (100) includes a connection system (122) configured to couple the unmanned air vehicle system (100) to the elongated guide element (50) so that the unmanned air vehicle system (100) is guided by the elongated guide element (50) as it flies between the first vertical station and the second vertical station within the internal tower space.

2. The wind turbine system (10) of Claim 1, wherein when the unmanned air vehicle system (100) is coupled to the elongated guide element (50), the connection system (122) is configured to restrain the unmanned air vehicle system (100) at a fixed separation distance from the elongated guide element (50).

3. The wind turbine system (10) of Claim 1, wherein when the unmanned air vehicle system (100) is coupled to the elongated guide element (50), the connection system (122) is configured to allow controlled movement of the unmanned air vehicle system (100) towards and away from the elongated guide element (50).

4. The wind turbine system (10) of Claim 1, wherein the connection system (122) is configured to permit the unmanned air vehicle system (100) to be coupled and decoupled from the elongated guide element (50).

5. The wind turbine system (10) of Claim 4, wherein the connection system (122) is configured to permit the unmanned air vehicle system (100) to be decoupled from the elongated guide element (50) when the unmanned air vehicle system (100) is located at a predetermined location within the internal tower space.

6. The wind turbine system (10) of any one of the preceding claims, further including a docking station (28) configured to dock with the unmanned air vehicle system (100), wherein the docking station (28) is located at the first vertical station.7 The wind turbine system (10) of any one of the preceding claims, wherein the elongated guide element (50) is attached at the first vertical station to the docking station (28).

8. The wind turbine system (10) of any one of the preceding claims, wherein the docking station (28) is provided at a passenger lift platform (54) of the internal tower space.

9. The wind turbine system (10) of any one of claims 1 to 5, wherein the elongated guide element (50) is attached at the first vertical station to a passenger lift platform (54) of the internal tower space.

10. The wind turbine system (10) of any one of the preceding claims, wherein the elongated guide element (50) also provides an alternative function to guiding the flightpath of the unmanned air vehicle system (100).

11. The wind turbine system (10) of Claim 10, wherein the elongated guide element (50) comprises a current-carrying cable and / or a data-carrying cable.

12. A wind turbine system (10) comprising a tower (14) and a nacelle (12) mounted to the tower (14) having an internal tower space, and a unmanned air vehicle system (100) adapted for inspection activities within the internal tower space,wherein the tower (14) is provided with a passenger lift system (26) including a passenger lift platform (54) adapted to be raised and lowered within the internal tower space,wherein the wind turbine system (10) further includes a docking station (28) configured to dock with the unmanned air vehicle system (100),wherein the docking station (28) is located on the passenger lift platform (54).

13. The wind turbine system (10) of Claim 12,wherein the passenger lift system (26) is configured to convey the docking station (28) to a predetermined vertical station within the internal tower space,and wherein the unmanned air vehicle system (100) is configured to disengage from the docking station (28) at the predetermined vertical station and perform an inspection activity.

14. The wind turbine system (10) of Claims 12 or 13,wherein the docking station (28) is provided with a charging system configured to charge the unmanned air vehicle system (100) when in a docked configuration.

15. The wind turbine system (10) of Claim 14, wherein the docking station (28) is further provided with one or more of:a communication system (38) configured to communicate with the unmanned air vehicle system (100);a positional beacon configured to broadcast the three-dimensional position of the docking station within the internal tower space.

16. The wind turbine system (10) of any of Claims 12 to 14, further comprising an elongated guide element (50) extending from the docking station (28) to a vertical station in the internal tower space,wherein the unmanned air vehicle system (100) includes a connection system (122) configured to couple the unmanned air vehicle system (100) to the elongated guide element (50) so that the unmanned air vehicle system (100) is guided by the elongated guide element (50) as it flies between the docking station (28) and the vertical station within the internal tower space.

17. The wind turbine system (10) of Claim 16, wherein when the unmanned air vehicle system (100) is coupled to the elongated guide element (50), the connection system (122) is configured to restrain the unmanned air vehicle system (100) at a fixed separation distance from the elongated guide element (50).

18. The wind turbine system (10) of Claim 16, wherein when the unmanned air vehicle system (100) is coupled to the elongated guide element (50), the connection system (122) is configured to allow controlled movement of the unmanned air vehicle system (100) towards and away from the elongated guide element (50).

19. The wind turbine system (10) of any one of Claims 16 to 18, wherein the connection system (122) is configured to permit the unmanned air vehicle system (100) to be coupled and decoupled from the elongated guide element (50).

20. The wind turbine system (10) of Claim 19, wherein the connection system (122) is configured to permit the unmanned air vehicle system (100) to be decoupled from the elongated guide element (50) when the unmanned air vehicle system (100) is located at a predetermined location within the internal tower space.

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