A system for tethering a drone to an anchor in flight

Abstract

Provided is a system for tethering a drone 100, the system comprising a mechanism 103 that is connected to the drone and that extends from an upper region of the drone towards a bottom region of the d

Description

FIELD The present invention relates to a system and method for improving the deployment, operation, and retrieval of an unmanned vehicle, such as a drone. In particular, the present invention relates to a system for tethering a drone and a method for deploying or retrieving a drone, the drone having a tethering system. BACKGROUND Continuous improvements in the field of unmanned vehicle design have led to unmanned vehicles such as drones becoming hugely useful tools for a wide range of commercial and recreational applications. For example, drones may serve as a hobby item, or, if equipped with one or more inspection instruments such as sensors - usually cameras, they have become invaluable in quickly and efficiently collecting inspection data across large spaces, including both within and outside of man-made structures, in the air, or even in water in the case of a submersible drone. In certain applications, it can be advantageous to affix a tether to a drone. A tether can be useful for providing a physical connection between the operator and the drone, or to provide an indication of the location of the drone to an operator. Additionally, tethers can provide a range of benefits during drone operation. For example, a tether can facilitate manual retrieval of the drone in the event of a system failure, or can be used to provide power or control signals to the drone during operation, thus reducing or eliminating the need for on-board energy storage, i.e. batteries, and avoiding some of the difficulties that can occur with radio frequency (RF) control. The provision of power to the drone via the tether also allows, in theory, for unlimited flight time of the drone, and hence can be a key advantage of tethering the drone. A tether can also allow signals to be returned to the operator through the tether, reducing or removing the drone’s reliance on RF data transmission or on on-board data storage. However, it has proven difficult to implement such a tether without negatively affecting the operation of the drone. Affixing a tether to the body of a drone has been found to have an adverse effect on the movement on the drone in most circumstances, and if improperly positioned, or if improperly controlled by the operator, such a tether may interfere with or obstruct one or more of the propellers of the drone. This risks damaging either the tether or the drone, and may result in a loss of control of the drone, or even a failure or loss of the drone, if the tether, the drone or just one or more of the propellers is sufficiently damaged. It would therefore be desirable to provide a system for tethering a drone that alleviates or resolves some of these issues. SUMMARY According to an aspect of the present invention there is provided a system for tethering a drone, the system comprising: a mechanism that is connected to the drone and that extends from an upper region of the drone towards a bottom region of the drone; a connector coupled with the mechanism and able to move along a length of the mechanism; and a tether connected to the drone and the connector, wherein a connection between the tether and the connector moves with the connector as the connector moves along the length of the mechanism. The above system is advantageous as it allows for a tether to be connected to the drone and for this connection to be maintained during operation of the drone without it being fixed to a fixed position on the drone. The ability of the connector and the tether to move along the length of the mechanism during flight, or, for example during start-up (e.g. during take off, or when first powering up the rotors, or shortly thereafter), allows for the connector, and thus a proximal end region of the tether (a region distal from the operator), to be positioned at a first advantageous position during the early stages of the start-up of the drone, and where it would be advantageous for this connector to be at a second advantageous position during flight, to move to said different position during flight. In some embodiments, this is such that it hangs below or clear of every propeller of the drone - for example under the drone, and hence this minimises flight interference from the tether. For example, this can be to ensure that the drone hovers "straight” in the air at start-up, i.e. when arming the drone, and even when disarming the drone (i.e. at the end of the flight), as well as to guide the tether towards the center under the drone during flight so that the tether has a minimal or zero effect on the balance of the drone during the flight. In some embodiments, the connector can move to an end point below the drone such that it becomes centrally connected to the base of the drone, and is thus substantially balanced under the drone, minimising its effect on the flight of the drone. In some embodiments, the system further comprises an anchor point, wherein the anchor point is connected to an opposite end of the tether from the drone. For example, the anchor point may be proximal to the operator, or may be the operator, or a control device for the drone, as operated by the operator. Typically the drone is an aerial drone. The drone may have at least one main propeller or rotor, for example a single main rotor with a tail rotor, like a helicopter, or it may have two or more propellers or rotors, for example being a twin rotored helicopter (with counter rotating rotors), tricopters (3 rotors), quadcopters (4 rotors), hexacopters (6 rotors) or octocopters (8 rotors), amongst others with additional or different propeller or rotor configurations, including either or both co-axial and non-coaxial rotor configurations. In some embodiments, the mechanism comprises a bracket. It may form a structure around the outside of the drone, clear of the main moving parts of the drone, such as the rotors. In some embodiments, the bracket is shaped such that it has at least one bend, around which the connector can move. In some embodiments, the bracket is shaped such that it bends around an external profile of the drone. In some embodiments, the bend arches around a lateral extreme of the drone. In some embodiments, a length of the tether is adjustable such that it may be extended or retracted during operation. The length of the tether may be manually adjusted by the operator. Adjustment of the tether’s length is advantageous as it allows the length of the tether to be increased during an outbound flight to increase the range of the drone from the operator, or through a structure, or for the length to be reduced during retrieval or a return flight of the drone. In some embodiments, the anchor point comprises a connection for a power supply and the tether comprises a power line, the power line extending throughout the tether and into the drone. Providing the power line allows the power line to provide power to the drone from the power supply. This provides the advantage of increasing the length of time the drone is able to fly uninterrupted, by removing the drone’s reliance on onboard power storage, and thus power constraints imposed thereby. The anchor point may also comprise a control system - for example, the above-mentioned control device. In some embodiments, the power line is configured to carry a control signal to the drone for instructing operation of the drone, and the operator uses the control system or the control device to input control instructions for the drone. The drone will have on-board control electronics to action the control instructions and perform instructed operations. In some embodiments the power line is configured to carry one or both of a control signal from the control system to the drone or a return signal from the drone to the controller, the power line being configured to carry one or both of the signals via modulation on the power line. The control signal may take the form of a modulated Ethernet signal carrying a control signal from the control system to the drone through the power line or a separate control cable, or it may be in some other form. In some embodiments, the control system may utilise RF signals or an alternative wireless protocol. In some embodiments, the drone may be pre-programed with control instructions before operation, or may utilise Al control. In some embodiments, the tether comprises a control line separate to the power line, such as the separate control cable. The control line may also extend throughout the tether, for example being wound or extended therewith or therethrough, to extend to the drone, wherein the control line is configured to carry a control signal to the drone from the control system. In some embodiments, the tether transmits data either from the drone to the anchor point or control system, or from the anchor point or control system to the drone, or both. This may be through the power line or through the control line or through a data line separate to the power line and the control line. The data line also extends throughout the tether from the drone to the anchor point or control system, wherein the data line is configured to provide a data connection from the drone to the control system, usually for return data. This return data may comprise inspection data obtained from one or more sensors on the drone. The sensors may be cameras or other information, surveying or inspection sensors. In some embodiments, the data signal can be piggybacked through either the power line or the control line, and in some embodiments the same line can carry all three signals - power, control and return data. In some embodiments, the anchor point further comprises a first transformer, wherein the first transformer is configured to increase the voltage of power from the power supply before transmission through the power line. In some embodiments, the drone comprises a second transformer, wherein the second transformer is configured to decrease the voltage of power from the power line before usage by the drone. These embodiments are advantageous as they allow the voltage to be increased through the power line, and thus for power losses through the power line to be reduced. This in turn allows the power line to be made thinner, which further reduces the drag-effect of the tether on the flight of the drone, and the cost of the power line. In some embodiments the voltage of the power through the power line is increased, for example to a voltage not exceeding 600V - for example to between 300 and 600V - for example to about 400V, and then down to between 3 and 50V in the drone - for example 24V or 48V. Common operating voltages in commercial or industrial inspection drones (for example for on-board electronics and / or the motors) are typically between 20 and 50 V, but other voltages are also possibly going to be required onboard. Advantageously the drone uses DC power. The power may delivered either as AC power or as DC power, with suitable converters provided where needed at either the drone or the anchor point / control system. In some embodiments, the connector is positioned at a first end of the mechanism during start-up of the drone, wherein the first end is vertically above a centre of gravity of the drone. This is particularly beneficial for when hanging the drone below the tether during take-off / start-up of the rotors. This can be a common launch condition when launching the drone in a pipe or chamber accessed through a manhole, a roof-hatch or the like. This might be for underground inspections, tank inspections or ship inspections. In particular, this can be for ship tank inspections where the tanks are below deck, with the access hole or manhole being on the deck. When instead taking off from the ground, the connector may instead be positioned elsewhere along the bracket - while still keeping the tether clear of the rotors. It is also possible for the connector to be at a bottom end of the bracket / mechanism during take off / start-up - e.g. if held by the bottom of the drone by a hand or launching pole during take off / start-up, such that the tether hangs below the drone. This may occur, for example, when hand launching the drone into a closed space, pipe or tank. In some embodiments, the connector is located at a second end of the mechanism during flight, or at least during the majority of a flight, allowing for the fact that it starts at the first end and has to move to the second end. In some embodiments the second end is vertically below a centre of gravity of the drone during take-off. It is usually the aim of the drone to fly during its flight with its vertical axis extending substantially vertical, although during flight this may lean away from vertical due to the need to generate forward, side or rearward thrust from the propellers or rotors. The second point is desired to be directly below the centre of gravity of the drone as that offers an optimal position for avoiding instability in the drone due to the weight of the tether. Locating the first and second points above and below the centre of gravity of the drone also minimises the effect of the tether on the flight of the drone, while still allowing the drone to be carried to its start-up point by the tether, or dropped to its start-up position using the tether. A typical launch scenario, however, is where the drone is hanging from the tether when launched, or held in the hand while launched. The connector’s position, and thus the position of the tether, can also play a key role during the recovery of the drone. For example, it may be desirable manually to keep the tether taut during recovery. This might be by shutting off the drone motors / rotors while the drone hangs from the tether. This allows the drone to be recovered by just lifting it from the tether through the narrow manhole. Alternatively the tether may be kept taut while the drone flies back towards the operator so that it does not snag on the rotors during that return flight (the operator and manhole is commonly above the drone during inspections, and thus the tether won’t be entirely (if at all) on the ground). In some embodiments, the mechanism comprises a stop at one or both ends of the mechanism, to define stopping points for the connector’s movement along the mechanism. In some embodiments the stop at a first end (first end region of the bracket) is connected to a first surface of the drone - for example a top of the drone, wherein the portion of the mechanism between the stop and the first surface has a width or height greater than a corresponding width or height of the connector, such that the connector cannot freely traverse along the mechanism beyond the stopping point. This is advantageous as it prevents the connector from becoming caught on an end portion of the mechanism, or moving beyond the top position in the wrong direction. In some embodiments, the mechanism comprises a retaining indent, for positioning the connector. For example, this may be at a bottom end of the mechanism. The retaining indent is configured to be suitable to encourage the connector to remain in the retaining indent on the bracket during flight. This is advantageous as it maximises the likelihood that the connector remains vertically below the centre of gravity of the drone in flight, which minimises the effect of the tether on the flight of the drone. In some embodiments, the mechanism is composed of a carbon fibre material. In some embodiments, the connector comprises a karabiner and a tether clamp, optionally wherein the karabiner is composed of aluminium. In some embodiments in which the mechanism is a bracket, the bracket comprises a hook at a first end and the drone comprises a hanging member, whereby the bracket can be connected to the drone by interlocking the hanging member with the hook. The drone, in use, hangs below the hook. In some embodiments, the bracket comprises a first hole at a second end and the drone comprises a second hole at its bottom region, wherein the bracket is connected to the drone at its second end by placement of a bolt or connector through the first hole and the second hole. The bracket may first hook the hanging member at its top, and it may then be rotated or swung down along and over the side of the drone to align the first and second holes underneath the drone. This configuration is advantageous as it allows for a secure connection between the bracket and the drone during flight, and it is also a simple procedure to connect the bracket to the drone. This configuration also allows for, simultaneously, a reliable mechanism to secure the bracket to the drone during operation and a simple method of connecting and disconnecting the bracket from the drone when not in operation. In some embodiments, the hook is free to move along an axis of the hanging member whilst these two components are connected together - for example during a flight. The axis may be substantially horizontal during the flight of the drone, as mentioned above, albeit potentially with some variation for generating thrust. This freedom to move is advantageous as it allows the hanging member to adjust its position with respect to the hook to adjust and find an optimal balance position for the drone on the bracket during flight, and this can adjust during flight depending on the specific conditions, thus optimising the stability of the drone during flight, and particularly during acceleration or directional changes of the drone’s flight. According to another aspect of the invention, there is provided a drone comprising a system for tethering, the system for tethering being in accordance with any of the embodiments described above or below. According to another aspect of the present invention, there is provided a method for deploying a drone, the drone having a tethering system comprising: a mechanism that is connected to the drone and that extends from an upper region of the drone towards a bottom region of the drone; a connector coupled with the mechanism and able to move along a length of the mechanism; and a tether connected to the drone and the connector, wherein a connection between the tether and the connector moves with the connector as the connector moves along the length of the mechanism; the method comprising: positioning the drone at a deployment position, and the connector at a first position on the mechanism; activating one or more propellers of the drone, the propeller, or propellers collectively, generating sufficient lift to support a weight of the drone; and subsequently wherein the connector moves along a length of the mechanism towards a second position on the mechanism. In some embodiments, the mechanism comprises a bracket (e.g. as previously described). In some embodiments, the connector can move to an end point below the drone such that it becomes centrally connected to the base of the drone, and is thus substantially balanced under the drone, minimising its effect on the flight of the drone. In some embodiments, the method comprises instructing, by a control signal, the drone to initiate travel in a direction, wherein during said travel the connector moves along the length of the mechanism towards the second end of the mechanism. In some embodiments, a length of the tether is increased during the travel such that the connector, the connection and the tether are encouraged to move along the length of the mechanism towards the second position on the mechanism. In some embodiments, the first position on the mechanism may be an end closest to the upper region of the drone. The second position may be an end closest to the bottom region of the drone. In some embodiments, the deployment position for the drone may be at, above or below an entry point to a structure, such as underground, or in a pipe or tunnel or enclosed space, for example accessed and / or deployed through a manhole. The drone may dangle from the tether when located in the deployment position. The entry point may be located in an upper region of the structure. The method may further comprise lowering the drone, for example into the structure through the entry point, before activation of the one or more propellers. The drone may be lowered by an operator of the drone, or by a lowering mechanism. In some embodiments, the control signal may be transmitted to the drone in real-time by an operator. The control signal may be transmitted through the tether. Alternatively, the control signal may be transmitted wirelessly to the drone. In other embodiments, the drone may be pre-programed with a sequence of control signals, or with such a sequence and instructions to react to avoid any sensed obstructions, prior to deployment, such that no control signals need to be transmitted to the drone during operation - for example with a pre-programmed flight path. The tethering system may be the system for tethering as defined above or below. According to another aspect of the present invention, there is provided a method for retrieving a drone, the drone having a tethering system comprising: a mechanism that is connected to the drone and that extends from an upper region of the drone towards a bottom region of the drone; a connector coupled with the mechanism and able to move along a length of the mechanism; and a tether connected to the drone and the connector, wherein a connection between the tether and the connector moves with the connector as the connector moves along the length of the mechanism; the method comprising: instructing, using a control signal, the drone to initiate movement towards a retrieval point, wherein the connector, the connection and the tether are situated at a second end of the mechanism; and decreasing a length of the tether such that the connector, the connection and the tether are encouraged to move along a length of the mechanism towards a first end of the mechanism. In some embodiments, the method comprises deactivating one or more propeller of the drone at the retrieval point. The drone may then be lifted from the retrieval point using the tether. In other embodiments, one or more propeller may be used to increase lift for the drone, and the drone is flown back towards an operator or a lowering mechanism, with the tether being maintained above the or each propeller of the drone. In some embodiments, the second end of the mechanism may be an end closest to the bottom region of the drone. The first end may be an end closest to the upper region of the drone. In some embodiments, the retrieval position may be at or below an exit point to a structure. The exit point may be located in an upper region of the structure. The method may further comprise raising the drone through the exit point, before deactivation of the one or more propeller. The drone may be raised by the one or more propellers of the drone, or by reversing the lowering mechanism. In some embodiments, the control signal may be transmitted to the drone in real-time by an operator. The control signal may be transmitted through the tether. Alternatively, the control signal may be transmitted wirelessly to the drone. In other embodiments, the drone may be pre-programed with a sequence of control signals, or with such a sequence and instructions to react to avoid any sensed obstructions, prior to deployment, such that no control signals need to be transmitted to the drone during operation - for example with a pre-programmed flight path to an inspection site and back to the retrieval point. In some embodiments, the method may further comprise instructing, using a control signal, the drone to move towards a landing point. The landing point may comprise a floor within a structure or elsewhere. One or more propeller of the drone may be deactivated at the landing point before decreasing, or further decreasing a length of the tether. In some embodiments, the drone flies to the landing point prior to the retrieval point. Then, after decreasing the length of the tether at the landing point, the one or more propeller may be reactivated, and the drone may be instructed to move towards the retrieval point. The decreasing of the length of the tether at the landing point can be to move the connector, the connection and the tether above the propeller(s) - for example to the first end of the mechanism. The tethering system may be the system for tethering as defined above or below. BRIEF DESCRIPTION OF THE DRAWINGS Embodiments of the invention will now be described, purely by way of example, with reference to the following figures. FIG. 1 shows a drone comprising a tethering system according to embodiments of the present invention, with a connector at a first end of a bracket of the tethering system. FIG. 2 shows an alternative angle of the drone of Fig. 1. FIG. 3 shows the drone with the connector and tether in a first intermediate position along the bracket. FIG. 4 shows the drone with the connector and tether in a second intermediate position. FIG. 5 shows the drone with the connector and tether at a second end of the bracket. FIG. 6 shows the power line connection between the tether and the drone from a front and a side view. FIG. 7 shows the power line connection between the tether and the drone with the connector at different positions along the bracket. FIG. 8 shows the bracket, separated from the drone. FIG. 9 shows a hanging member for the drone, for connecting onto the bracket’s first / upper end. FIG. 10 shows four steps A to D in a process of connecting the hanging member of the drone onto the first end of the bracket. FIG. 11 shows two subsequent steps in the process, involving bolting the second end of the bracket to a base of the drone. DETAILED DESCRIPTION OF EMBODIMENTS Fig. 1 shows a drone 100 comprising the tethering system 101. The tethering system 101 comprises a mechanism 103, a connector 105, and a tether 107. In the embodiment of Fig. 1, the mechanism 103 comprises a bracket. However, it is to be understood that other suitable mechanisms for adjustably attaching the tether to the drone may be suitable, such as tracks and rails. The bracket 103 is connected to the drone 100 at at least one point - in this embodiment it is attached at both its ends. The bracket extends from an upper region of the drone 100 to a bottom region of the drone 100. The bracket 103 may be connected at the upper region of the drone 100, and / or the bottom region of the drone 100. In some embodiments, such as the one in Fig. 1, the bracket 103 may be shaped such that it bends at various points along its length to curve around the side of the drone. The bracket 103 usually is bent to substantially match or follow an external profile of the drone. In this embodiment, the bracket is substantially straight between the bends and the bends are smoothed curves relative to the straight sections to provide a surface along which the connector may slide, as discussed below. In other embodiments, the bracket 103 may be straighter or more curved. The connector 105 comprises any suitable connection device for linking the tether 107 to the bracket 103. The connector 105 is coupled to the bracket 103 such that it is freely able to traverse a length of the bracket 103, from a first end to a second end, and vice versa - in this embodiment those ends being from the upper region of the drone to the bottom region of the drone, and back again. The connector 105 is further coupled to the tether 107, such that the tether 107 is similarly able to traverse a length of the bracket with the connector. In this embodiment the connector encircles the bracket to slide there-along, like a curtain ring. Other slide mechanisms for the connector 105 could instead be adopted. In the embodiment shown in Fig. 1, the connector 105 comprises a karabiner affixed to a tether clamp. The karabiner is connected around the bracket 103, such that the karabiner is secured to the bracket 103 during operation but able to move along its length. The karabiner is affixed to the tether clamp. The tether 107 extends through an interior volume of the tether clamp to be retained thereby, such that movement of the connector moves also the tether clamp, which in turn moves the tether 107. The tether clamp may be sufficiently clamped onto the tether such that the tether 107 cannot move within the tether clamp. By facilitating movement of the connection of the tether 107 to the connector along the length of the bracket 103, negative effects of weight and bulk of the tether 107 on the flight of the drone 100 can be minimised. For instance, the connector 105 and tether 107 can naturally traverse the bracket 103 during operation of the drone to find a more advantageous position than the top of the drone, such as below propellers of the drone, e.g. the bottom region of the drone. By allowing this movement, the freedom of movement of the drone 100 during its intended flight is improved. Further, by positioning the tether below the propellers, the tethering system 101 ensures that the tether 107 is prevented from interfering with one or more of the propellers of the drone 100 during that flight. The tether 107 extends away from the bracket and the drone 100 to an anchor point 200. The anchor point 200 may be an operator. In some embodiments, the anchor point 200 comprises a base station. The base station may be manned by an operator, who may be present at the base station or operating remotely. The length of the tether 107 may be adjustable during operation of the drone. The anchor point 200 may comprise a reel, or another suitable tether collection / winding mechanism for allowing the length of the tether 107 to be increased or decreased. By increasing and decreasing the length of the tether 107, the tether 107 and connector 105 can be encouraged into advantageous positions along the bracket 103 during flights. This will be explained further with reference to figures 2 to 5. Operation of the drone 100 commences with using a start-up process. A number of suitable start-up processes exist. In some embodiments, the drone 100 may first be positioned on a surface, such as a floor or ground. In these embodiments, the drone 100 may take-off directly from the ground. For this process, it is advantageous for the connector 105 and tether 107 to first be positioned such that they are located at a position on the bracket which is not directly underneath the drone 100, such that the drone 100 can be placed onto the surface and take-off without interference from the tether (e.g. the feet fouling against the tether). Upon take-off of the drone, the connector 105 and tether 107 may then move under the effect of gravity, or through the movement of the drone, to a point directly underneath the drone 100. The tether then becomes centrally connected to the base of the drone, and is thus substantially balanced under the drone, minimising its effect on the flight of the drone. In an alternative start-up process, the drone 100 may be deployed into a structure from an entry point on a top side of the structure. In these embodiments, the drone 100 may be carried, either manually by one or more operators or by the tether 107, such that the drone is suspended over / under the entry point. The drone may then be deployed from this position into or through the structure. For this process, it is advantageous for the connector 105 and tether 107 to first be positioned such that they are located at a top most position on the bracket, so that the drone 100 can hang level before its deployment. Upon deployment of the drone into or through the structure, the connector 105 and tether 107 may move under the effect of gravity and / or the movement of the drone, to a point directly underneath the drone 100. In another alternative start-up process, the drone 100 may be deployed from an alternative deployment mechanism, such as a pole. The drone 100 may be removably connected to an end of the pole, before being suspended from or lifted by, the pole at a point above or below the ground. Once suspended or so lifted, the drone may take-off from the pole, detaching from the pole for onward flight. In these embodiments, the tether 107 and the connector 105 can advantageously be positioned elsewhere along the bracket 103 to avoid having the tether cause an interference with the take-off, before moving under the effect of gravity, or movement of the drone, to a point directly underneath the drone 100 for the remainder of the flight (or until it needs to be moved again for drone recovery). Figs. 2 to 5 show the drone 100 comprising the tethering system 101 during different states of operation. Fig. 2 shows the drone 100 at a first time - for example a time of positioning the drone into a position for launch or deployment from a topside entry point. Deployment of the drone 100 may involve substantial movement of the drone in a vertical and / or horizontal plane. For instance, where the drone 100 is launched from the ground, deployment of the drone 100 may involve activation of one or more propellers to lift the drone 100 from the ground. However, in embodiments where the drone 100 is to inspect a structure such as a storage tank or pipe / tunnel, as discussed above the deployment of the drone 100 may involve lowering the drone through an entry point in a topmost exterior surface of the structure, or a manhole. The drone may be manually lowered through the entry point by an operator, or instead lowered by a lowering mechanism - which lowering mechanism may utilise the tether collection / winding mechanism above. Where deployment involves movement in a vertical plane, and the operator or tether is above the drone, it is advantageous to ensure that the tether 107 is positioned in such a way that it cannot interfere with the flight of the drone. Hence, at the time of launch or deployment, it is advantageous for the connector 105 and tether 107 to be in a top position - at the first end 110 of the bracket. In this top position, the connector 105 is located at the end of the bracket 103 that is closest to the upper region of the drone. This first end 110 may be such that the connector 105 and the tether 107 are located vertically above a centre of gravity of the drone. The tether 107 may be taut, such that the tether 107 extends upwardly away from the drone. The tether 107 may be held taut by a suitable mechanism at the anchor point 200, such as the reel, or it may be manually held taut by an operator at the anchor point 200. Deployment of the drone may involve an arming step. The arming step comprises supplying power to some or all of the propellers of the drone, in preparation for self-propelled movement of the drone. When arming the drone, it is advantageous for the drone to be kept level, such that the propellers are in substantially a horizontal plane -otherwise, the drone may be required to undergo additional calibration or control operations once it has been deployed to correct for the lateral acceleration of the startup. By using the tether to hang the drone with its propellers in their horizontal plane during the arming process, it can be ensured that the drone is kept level, and hence ensure a more successful deployment of the drone - important given the often confined spaces in which it will be deployed during pipe or tank inspection operations. Fig. 3 shows the drone 100 at a second time - after deployment of the drone 100. At this second time, the drone 100 may now be in flight, and hence the drone may undergo a substantial amount of lateral movement in a horizontal plane. Operation of the drone is of course not limited to lateral movement in a horizontal plane, but rather operation of the drone typically involves more lateral movement than the initial deployment or take-off of the drone. At this second time, the length of the tether 107 can be increased. The length of the tether 107 can be increased manually by an operator, or automatically by a suitable mechanism at the ground station or anchor point, such as the reel. Adjustments to the length of the tether 107 may have already occurred to accommodate for the movement of the drone 100 during take-off or deployment, with the tether remaining taut. However, during the flight, the length of the tether 107 may be increased in such a fashion as to introduce slack into the tether 107, such that the tether 107 no longer remains taut in its initial position. This introduction of slack allows for the tether 107 and connector 105 to move / slide along the bracket 103. For example, under the effect of gravity, or forces introduced due to the movement of the drone during its flight, the connector and tether move along the bracket to a new first intermediate position 111 on the bracket 103. Fig. 4 shows the drone 100 at a third time. The introduction of slack into the tether 107 by increasing its length has resulted in the connector 105 and tether 107 moving to a new intermediate position 112 on the bracket 103. It is to be understood that intermediate positions 111 and 112 represent two of many intermediate positions during movement / sliding of the connector and tether along the length of the bracket 103, and are displayed in these figures for the purposes of explanation only. Fig. 5 shows the drone 100 at a fourth time, being later than the first, second and third times. The length of the tether 107 has now been increased sufficiently that that the connector 105 and tether 107 have moved to the second end 113 of the bracket 101. In this position, an inflight position, the connector 105 is located at the second end of the bracket 103, which is the end thereof that is closest to the bottom region of the drone. This position may be such that the connector 105 is vertically beneath a centre of gravity of the drone. At the fourth time, the length of the tether 107 has been increased such that the tether now hangs under the propellers of the drone with a sufficient degree of slack that it hangs clear of the drone. Allowing such an amount of slack in the tether is advantageous, as this reduces the impedance or drag on the movement of the drone during flight. Introduction of slack in a tether attached to a drone by conventional means would run significant risk of the tether interfering with the drone, either by getting caught on the drone or interfering with the propellers of the drone. However, due to the connector 105 being now at the second position - underneath the propellers, the tether 107 is able to hang with a significant clearance from the drone’s propellers, and thus minimising or eliminating all significant interference of the flight of the drone 100. Hence, the tethering system 101 as disclosed herein facilitates the movement of the connector 105 and tether 107 between a first position at the first end of the bracket, which position is advantageous for deployment when the drone is being dropped to a launch site, and a second position at the second end of the bracket, which position is more advantageous for flight. Figs. 2 to 5 illustrate the movement of the connector and tether as the drone 100 goes from deployment to operation. It is to be understood that a substantially similar sequence of events occurs in reverse during retrieval of the drone 100. When the drone is to be retrieved, operation of one or more propellers of the drone 100 may be decreased as the length of the tether 107 is decreased. This results in the drone lowering or landing, while the connector 105 and tether 107 move from position 113 to 110 along the bracket 103. During this process, in some circumstances the drone may be being landed onto the ground while the length of, or slack in, the tether 107 is decreased. In others, the tether’s length may be being reduced without an actual landing. For example, depending upon the situation of the inspection process, the drone can be retrieved from pipe or chamber to the topside or outside (e.g. through a doorway, a hatch or a manhole) with or without first landing on the ground. However, if the drone were to be landed with the connector 105 and tether 107 located at the second position at the second end of the bracket 103, the presence of the connector and tether underneath the drone could result in an unstable landing, possibly leading to the drone overturning. Hence, it is advantageous to reduce the length of the tether 107 such that it is manoeuvred into a position closer to the first end of the bracket 107 above the drone, to avoid interference with the landing by the tether. Once the connector 105 and tether 107 are in the uppermost position 110 (at the first end) and the tether 107 is taut, the drone 100 may be piloted towards a retrieval point. The retrieval point will typically be the entry point by which the drone 100 entered the structure. In some embodiments, some or all of the propellers of the drone may be deactivated, and the drone may be retrieved manually by retracting the tether 107. The tether 107 may provide a number of advantages in operation of the drone 100. In a first embodiment, the tether 107 may simply comprise a length of rope or cord, connecting the drone 100 to an anchor point 200. In these embodiments, the tether 107 may provide a visual and / or tactile indication to an operator at the anchor point 200 of the current location of the drone 100. In some embodiments, the tether 107 may be comprised of a material strong enough to support a weight of the drone 100. In these embodiments, the tether allows for the manual retrieval of the drone 100 in the event of drone failure during operation. For example, where the drone 100 has entered a structure from above, only for the drone to malfunction whilst inside the structure, an operator located towards a top of the structure, or at the anchor point, may use the tether 107 to manually lift or retrieve the drone 100 through and out of the structure. This may occur in scenarios where the drone propellers are intentionally deactivated also. The length of time the drone 100 is able to operate for is limited by, amongst other things, the power supplied to the drone. The drone 100 may comprise a battery, wherein the battery provides power to the drone during operation. However, in these embodiments, the operation time of the drone is limited by the amount of power stored by the battery. Furthermore, it is advantageous for a drone 100 to be relatively light weight, and hence the inclusion of large batteries can have a negative effect on the operational characteristics of the drone. Hence, in some embodiments, the tether 107 may further comprise a power line for feeding power to the drone, thus avoiding the requirement for batteries on-board the drone, or allowing smaller batteries to be used. Fig. 6 illustrates a possible implementation of the connection of the power line 109 from the connector to the drone itself. Part A of Fig. 6 shows a front view of the drone 100 with the power line 109 extending out of the tether 107 and into the drone at a connection point 210. Part B of Fig. 6 shows a side view of the same. The power line 109 may extend from the anchor point 200 throughout the tether 107 and into the drone 100. By virtue of the movement of the tether 107 and connector 105, the power line 109 may be kept clear of the propellers of the drone 100. The power line 109 may serve to electrically connect the drone 100 to a power source present at the anchor point 200. The power source may comprise a battery, a generator, or a mains power supply. With a power line 109, the operation time of the drone 100 may be increased without requiring the placement of more power sources on the drone itself, maintaining a lower weight of the drone 100. The requirement for batteries on the drone might even be eliminated if all systems are powered by power from the power line. This can then allow the drone to be smaller and more manoeuvrable. Fig. 7 shows two more front views of the previously described implementation, with the connector 105 at different points along the bracket 103. As can be seen from Fig. 7, the power line 109 is such that it extends out of the tether 107 and into the drone 100 whilst avoiding interference with the propellers of the drone 100. The previous figures refer to the power line connection from the tether to the drone, but it is to be understood that the above may also be understood to show an example of a data line connection or a control line connection also. For example, the tether may be continuous to the connection point 210 on the drone. It is advantageous for the tether 107 to be made as thin and lightweight as possible, to reduce the drag of the tether on the flight of the drone 100. However, the resistance provided by a power line is increased where the power line has a smaller cross sectional area, and hence the deliverable amount of power carried by the power line may be negatively affected by reducing its thickness. To counter this, the anchor point 200 may comprise a transformer, coupled between a power source and the power line. The transformer is configured to increase the voltage of power from the power supply before it is carried to the drone by the power line. For example, for mains power at either 110V or 240V, the voltage may first be increased to a higher voltage - usually one that does not exceed 600V, for transmission through the power line. Usually it will be delivered through the power line at about 400V. By increasing the voltage of the power delivered through the power line, the problem of a higher resistance caused by a thinner wire can be counteracted, as the higher voltage results in a lower current for the same amount of power delivery. A smaller cable can thus be used while still ensuring an adequate amount of electrical power can be delivered to the drone. In these and other embodiments, the drone 100 may also comprise a transformer. The transformer on the drone is configured to decrease the voltage of power provided to the drone 100 by the power line to a voltage suitable for the electronics of the drone 100. For example, the voltage may be decreased to between 3 and 48V in the drone. In typical examples, the voltage may be decreased to a variety of voltages for different elements in the drone - for example, one or more of 5V, 7.4V, 12V, 14.8V, 24V and 22.2V, for use by the various electrical components of the drone, including the propellers, the control electronics and any sensors. In some embodiments, the drone 100 may comprise a processing unit, and the processing unit may be pre-programmed with a flight path and control instructions for the drone during operation. However, more typically, the tether 107 carries control signals to the drone for operational control of the drone by an operator or remote control system. This may be carried out by the tether further comprising a control line. The control line may be connected to a control system present at the anchor point 200, and provides control signals to the processing unit of the drone 100, whereby the processing unit does not need pre-programming. In such embodiments, the control system may be operated by an operator, allowing for real-time control of the drone. Alternatively, the control system may be configured to provide pre-determined control signals to the drone 100. In some embodiments, the tether 107 may not comprise a separate control line. This may be because the processing unit on the drone is pre-programmed with instructions, and hence does not require control signals. Alternatively, the anchor point 200 may comprise a wireless transceiver, wherein control signals may be transmitted to the drone 100 via radio frequency or another suitable wireless protocol and received by a transceiver on the drone. In other embodiments this may be because the control signals are transmitted through the power line - piggybacking the power feed. In some embodiments, the drone needs to feed data back to the operator or control system. For this purpose the tether 107 may comprise a data line. The data line may be configured to transmit return data from the drone 100 to a control system at the anchor point 200. In some embodiments, the return data may comprise an operational status of the drone. In some embodiments, the drone may comprise one or more sensors, such as a camera. In these embodiments, the data line may transmit return data from the one or more sensors to the control system for storage or review - for example by the operator. In some embodiments, the control line, the data line and the power line are all separate lines within the tether. In other embodiments, a singular transmission line may allow for the transmission of control signals to the drone and return data from the drone. In some embodiments, the control signals and / or return data may be carried by the power line. Various protocols can be utilised for transmission of power, data and control signals. In some embodiments this may be through Ethernet modulation of the signals to facilitate their transmission on the power line. The skilled person will readily understand that different combinations of the above scenarios are suitable depending on the desired operational characteristics and capabilities of the drone. Referring now to Figure 8, an example mechanism in the form of a bracket 103 for attachment to the drone is shown. The bracket 103 may be made of a number of suitable materials. In some embodiments, the bracket 103 may be made of carbon fibre, aluminium or plastic, for example glass-reinforced plastic. As shown in Fig. 8, the length of the bracket extends between its first end 120 and a second end 123. The first end 120 of the bracket corresponds with the top position 110 of the connector 105 and tether 107, whilst the second end 123 of the bracket corresponds with bottom position 113 of the connector 105 and tether 107. The length of the bracket is configured with a suitable cross-section to allow the connector 105 to freely traverse its length without substantial resistance, and to provide adequate rigidity to support any forces intended to be encountered between the tether and the drone during deployment, flight and retrieval. The bracket is also intended to be relatively lightweight so as not to excessively hinder the flight capabilities of the drone. In Fig. 8, the bracket is configured such that the first end 120 is substantially above a centre of gravity of the drone and the second end 123 is substantially below a centre of gravity of the drone, such that the first and second ends of the bracket are vertically aligned. According to the bracket of Fig. 8, during operation, the first end 120 is positioned above a top surface of the drone and the second end 123 is positioned below a bottom surface of the drone. This is not a requirement of the invention, however - embodiments of the tethering system may comprise a bracket in which the second end is not vertically aligned with the first end, and / or in which the second end is not below a bottom surface of the drone, whilst still realizing the advantages of the invention - the slideability of the connection between the tether and the bracket - for allowing the tether to be better positioned for flight versus its position for vertical upward retrieval, or vertical downward deployment. Similarly, whilst the bracket 103 shown in Fig. 8 is such that it is bent at a point along the length to fit around the profile of the drone 100, this is again not required for embodiments of the invention to provide an advantage. In other embodiments, the bracket 103 may be shaped such that it is substantially straight. The bracket 103 may comprise a stop 125 at one or both of its end regions. The stop 125 at the first end is a portion of the bracket 103 comprising at least one dimension larger than the corresponding dimension of the connector 105, such that the connector 105 is unable to traverse along the bracket beyond the stop 125. The stop 125 shown in Fig. 8 comprises a triangular extension to the bracket 103, between the first end of the bracket 120 and a point of the bracket connecting to the drone 100. The stop 125 shown in Fig. 8 has a central portion cut out from within the triangle for the purpose of reducing the overall weight of the bracket. At the bottom, another stop is provided - a bend at the bottom end. This serves as a stop as the end is attached to the bottom of the drone, thus providing a point beyond which the connector cannot slide. The bracket 103 in this embodiment also comprises a retaining indent 127 at the bottom end. The retaining indent 127 is a portion of the bracket 103 in which a topmost surface of the bracket undergoes a slight vertical depression, such that the topmost surface of the bracket at that point is lower than an adjacent portion of the bracket 103. By implementing a retaining indent at the bottom end - the second end - of the bracket, the connector 105 can be encouraged under the effects of gravity to remain in a given position during flights. For example, by implementing a retaining indent 127 at the second end of the bracket, the connector 105 is more likely to be retained in position 113 during the flight as the indent serves as a gravity operated retainer for the connector. The retaining indent 127 should be shallow enough that the connector 105 is only encouraged into the corresponding position, and can easily be manoeuvre out of the indent when required, for example when the length of the tether is decreased during retrieval, simply through the removal of excess slack in the tether. In this embodiment the retaining indent is adjacent the bottom’s stop. The bracket 103 may be connected to the drone 100 by any number of suitable mechanisms. Fig. 8 displays an example of a bracket 103 shaped for connection to the drone 100 in the upper region by a hook 129 and in the bottom region by a bolting mechanism using a hole 131. An explanation of these example mechanisms will now be provided with reference to Figs. 9, 10 and 11. Fig. 9 shows an example of a hanging member 140. The hanging member 140 is a component of the drone 100, and may be disposed at one of the drone’s surfaces. In Fig. 9, the hanging member is located at the top surface of the drone 100. Fig. 10, parts A to D show four steps of connecting the bracket 103 to the top of the drone 100 via the hook 129 and the hanging member 140. As can be seen from parts A and B, the hanging member 140 can be manoeuvred into an interior space of the hook 129 via a gap in the hook 129. Once the hanging member 140 is within this interior space, the hook 129 can be rotated, as shown in part C. Once the hook 129 has been rotated, the hook 129 can be moved in a direction of the hanging member 140, such that the hanging member 140 is moved into a holding space of the hook 129, as shown in part D. The holding space of the hook may comprise a slot having a cross-sectional shape that is substantially the same shape and size as the cross section of the hanging member 140, such that the holding space retains the hanging member once inserted therein. In Figs. 9 and 10, the hook 129 is connected to the hanging member 140 in such a way that it is possible for the hook 129 to move forwards or backwards (longitudinally) along the hanging member 140 during operation, but not transversely (perpendicular to the longitudinal direction). This allows the hook 129 to naturally find an optimal position on the hanging member 140 during operation, such that the drone can hang from the top of the bracket in a more balanced manner. However, in some embodiments the hanging member may comprise a slot substantially the same thickness as the hook, such that when the hook is inserted into the slot in the hanging member, it is not free to move either longitudinally or transversely. For this, the locating position for the hanging member relative to the hook can be an optimally balanced position previously ascertained for a target form of drone for the bracket. The rotation of the bracket 103 in part C of Fig. 10 can result in the alignment of a second end of the bracket 123 with a connecting mechanism in the bottom region of the drone. An example of this is shown in Fig. 11, where parts A and B show an attachment process for the bottom of the bracket. Figure 11, part A, shows the second end 123 of the bracket 103 as shown in Fig. 8, when the first end 110 is connected via the hook to the drone 100. The rotation of the bracket 103 results in a hole 131 in the second end 123 of the bracket coming into alignment with a hole in a bottom region of the drone 100. The alignment of these two holes allows for a bolt 133 to be placed through the holes, and secured by a nut on the other side, as shown in Fig. 9, part B. This mechanism provides a secure connection between the bracket 103 and the drone 100 during operation of the drone. The above embodiment provides examples of a suitable mechanisms for securing the bracket 103 to the drone 100. The skilled person would readily appreciate that other methods and configurations for affixing the bracket 103 to the drone 100 may be equally suitable. While certain embodiments have been described above, these embodiments have been presented by way of example only and are not intended to limit the scope of the invention. Indeed, the novel methods, devices and systems described herein may be embodied in a variety of forms; furthermore, various omissions, substitutions and changes in the form of the methods and systems described herein may be made without departing from the scope of the invention as defined in the appended claims.

Claims

1. A system for tethering a drone, the system comprising:a mechanism that is connected to the drone and that extends from an upper region of the drone towards a bottom region of the drone;a connector coupled with the mechanism and able to move along a length of the mechanism; anda tether connected to the drone and the connector, wherein a connection between the tether and the connector moves with the connector as the connector moves along the length of the mechanism.

2. The system of claim 1, wherein the mechanism comprises a bracket3. The system of claim 2, wherein the bracket is shaped such that it has at leastone bend, optionally wherein it bends around an external profile of the drone.

4. The system of any one of the preceding claims, wherein a length of the tether is adjustable, such that the tether may be extended or retracted during operation.

5. The system of claim 4, wherein the length of the tether may be manually adjusted by an operator.

6. The system of any one of the preceding claims, further comprising an anchor point, the anchor point connected to an opposite end of the tether from the drone.

7. The system of claim 6, wherein the anchor point comprises a connection for a power supply and the tether comprises a power line, the power line extending throughout the tether and into the drone.

8. The system of claim 6 or claim 7, wherein the anchor point comprises a control system.

9. The system of claim 8, wherein the power line is configured to carry one or both of a control signal from the control system to the drone or a return signal from thedrone to the controller, the power line being configured to carry one or both of the signals via modulation on the power line.

10. The system of claim 8, wherein the tether comprises a control line, separate to any power line, the control line extending throughout the tether to extend to the drone, wherein the control line is configured to carry a control signal to the drone from the control system.

11. The system of any one of claim 8 to 10, wherein the tether comprises a data line, separate to the power line, the data line extending throughout the tether from the drone to the anchor point or the control system, wherein the data line is configured to provide a data connection from the drone to the control system.

12. The system of any one of the preceding claims, when dependent upon claim 7, wherein the anchor point comprises a first transformer, the first transformer configured to increase a voltage of power from the power supply before transmission through the power line.

13. The system of claim 12, wherein the first transformer increases the voltage to between 300V and 600V before power line transmission.

14. The system of any one of the preceding claims, when dependent upon claim 7, wherein the drone comprises a second transformer, the second transformer configured to decrease a voltage of power from the power line before usage by the drone.

15. The system of claim 14, wherein the second transformer decreases the voltage to between 3V and 50V before usage by the drone.

16. The system of any one of the preceding claims, wherein the connector is positioned at a first end of the mechanism during start-up of the drone and the first end of the mechanism is vertically above a centre of gravity of the drone during take-off.

17. The system of any one of the preceding claims, wherein the connector is located at a second end of the mechanism at least during a majority of a flight, wherein the second end is vertically below a centre of gravity of the drone during take-off.

18. The system of any one of the preceding claims, wherein the mechanism comprises a stop at one or both ends.

19. The system of any one of the preceding claims, wherein the mechanism comprises a retaining indent for positioning the connector at one or both ends of the mechanism.

20. The system of any one of the preceding claims, wherein the connector comprises a karabiner and a tether clamp.

21. The system of any one of the preceding claims, wherein the mechanism comprises a bracket, and wherein the bracket comprises a hook at a first end and the drone comprises a hanging member, whereby the bracket can be connected to the drone by interlocking the hanging member with the hook.

22. The system of claim 21, wherein the bracket comprises a first hole at a second end and the drone comprises a second hole at the bottom region, wherein the bracket is connected to the drone at its second end by placement of a bolt or connector through the first hole and the second hole.

23. The system of claim 21 or claim 22, wherein the hook is free to move along a length of the hanging member whilst the hook and the hanging member are connected together.

24. A drone comprising a system for tethering, the system for tethering being in accordance with any one of the preceding claims.

25. A method for deploying a drone, the drone having a tethering system comprising:a mechanism that is connected to the drone and that extends from an upper region of the drone towards a bottom region of the drone;a connector coupled with the mechanism and able to move along a length of the mechanism; anda tether connected to the drone and the connector, wherein a connection between the tether and the connector moves with the connector as the connectormoves along the length of the mechanism;the method comprising:positioning the drone at a deployment position, and the connector at a first position on the mechanism;activating one or more propeller of the drone, the propeller, or propellers collectively, generating sufficient lift to support a weight of the drone; andsubsequently wherein the connector moves along a length of the mechanism towards a second position on the mechanism.

26. The method of claim 25, wherein the connector moves to an end point below the drone such that it becomes centrally connected to the base of the drone, and is thus substantially balanced under the drone, minimising its effect on the flight of the drone.

27. A method for retrieving a drone, the drone having a tethering system comprising:a mechanism that is connected to the drone and that extends from an upper region of the drone towards a bottom region of the drone;a connector coupled with the mechanism and able to move along a length of the mechanism; anda tether connected to the drone and the connector, wherein a connection between the tether and the connector moves with the connector as the connector moves along the length of the mechanism;the method comprising:instructing, using a control signal, the drone to initiate movement towards a retrieval point, wherein the connector, the connection and the tether are situated at a second end of the mechanism; anddecreasing a length of the tether such that the connector, the connection and the tether are encouraged to move along a length of the mechanism towards a first end of the mechanism.

28. The method of claim 25, claim 26 or claim 27, wherein the tethering system is the system for tethering as defined in any one of claim 1 to 23.

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