Patent Description:
Unmanned aerial vehicles are generally well known, and include drones, rotorcopters, quadcopters, octocopters and the like. Such vehicles are typically provided with an electric motor which drives one or more rotors. The electric motor allows good mobility and manoeuvrability. However, it is difficult to generate a large lift thrust with these conventional vehicles.

In particular, as the payload ratio grows there is a diminishing return in practical range as the required source of electrical power must vastly increase in size. Typically lithium ion batteries are used as a source of electrical power for the electric motors. Such lithium ion batteries can store energy at approximately <NUM> MJ/kg. Therefore, the electrically driven rotors result in a relatively poor endurance and flight range for loads above a minimal weight.

This limitation is not an issue for many applications where there is little or no load to be lifted.

Given the ease of use of drones in remote locations and inaccessible terrain there is a need for drones which are able to assist in heavy lifting. Such assistance may be useful in construction, military deployment or extraction and operations, rescue operations, commercial delivery, or the like.

There is therefore a need for an improved drone which can assist with heavy lifting.

<CIT> discloses a system and method for a short take-off and landing or vertical take-off and landing aircraft that stores required take-off power in the form of primarily an electric fan engine, and secondarily in the form of an internal combustion engine.

<CIT> discloses methods and apparatus to cooperatively lift a payload.

<CIT> discloses an unmanned aerial vehicle which can deliver a package to a delivery destination.

An unmanned aerial vehicle according to a first embodiment of the present invention is provided according to claim <NUM>.

This unmanned aerial vehicle allows the electric flight rotors to be used for the high precision manoeuvrability required for general flight while the gas turbine propulsion system is used to provide lift for lifting a heavy load. This therefore allows the unmanned aerial vehicle to lift a heavy load while maintaining manoeuvrability during flight.

The load system may comprise a plurality of gas turbine propulsion systems. A plurality of gas turbine propulsion systems can increase the amount of thrust available to lift the load.

The gas turbine propulsion systems may be arranged with N-fold rotational symmetry in the plane of the flight rotors around a centre of the unmanned aerial vehicle, wherein N is the number of gas turbine propulsion systems.

The rotational symmetry of the gas turbine propulsion systems allows these systems to balance one another and provide a force simply to aid in the lifting of the load which not affecting the flight of the unmanned aerial vehicle.

Each gas propulsion system may be provided at an angle with respect to the thrust direction of the flight rotors. The angle directs the gas propulsion systems to counteract the load and not affect the flight of the vehicle. Additionally, the jet plume does not impinge upon any load being carried.

Each gas turbine propulsion system may comprise a ducted fan for producing the additional thrust in the form of its exhaust gas jet. Thrust in the form of exhaust gas jet is a thrust to weight efficient manner of generating additional lift.

The gas turbine propulsion system may comprise a turbojet; turbofan; or turboprop. These gas turbine propulsion systems are good methods to generate additional lift for a relatively low weight.

The flight system may comprise two or more rotors, arranged at an outer periphery of the unmanned aerial vehicle, preferably the flight system comprises four or eight rotors. Having the rotors arranged around the periphery of the unmanned aerial vehicle allows for enhanced manoeuvrability of the vehicle.

Each gas turbine propulsion system may be provided within a radius defined by the rotors. As the gas turbine propulsion systems is provided within the radius defined by the rotors the force it generates can be more easily balanced.

The controller may comprise: a first control system configured to control the flight system; and a second control system configured to control the load system, wherein the first and second control systems are independent of one another.

This allows the flight system to be used for the high precision manoeuvrability required for flight while the load system is used to provide lift for lifting a heavy load. This therefore allows the unmanned aerial vehicle to lift a heavy load while maintaining manoeuvrability during flight. Separating the first and second control systems allows the controller to effectively and efficiently provide additional thrust when necessary to lift the device separate to the flight control system.

The unmanned aerial vehicle further comprises: a load sensor in communication with the controller, the load sensor being configured to provide a signal indicative of the weight applied by a load attached to the connection point; wherein the controller is configured to control the load system in response to the signal indicative of the weight applied to the connection point.

The controller may be configured to control the load system in a closed-loop control to balance the force provided by the load system and the weight applied to the connection point. By balancing the weights the flight control system can operate as if the additional weight is not attached.

The unmanned aerial vehicle may have a first mode of operation in which the flight system is operated to take-off and/or land the unmanned aerial vehicle and in which the load system in inactive. By only operating the flight system during take-off and landing the risk of foreign object damage (FOD) is reduced as the load lifting propulsion units which are most likely to affected by FOD are not activated until the unmanned aerial vehicle is further from the ground.

The unmanned aerial vehicle may further have a second mode of operation in which the load system is activated to provide thrust equal to the weight of a load, and in which the flight system is used to generate thrust to manoeuvre the unmanned aerial vehicle and load. The load system thus counters the weight of the load and the flight system can simply be used to fly the unmanned aerial vehicle.

The cargo area may be provided at a centre of the unmanned aerial vehicle. By providing the cargo area at the centre of the unmanned aerial vehicle the load applied by the weight is applied centrally which aids the counterbalancing of this weight with the load system.

The cargo area comprises a connection point and may further comprise a tether. The use of a tether allows the slack in the tether to be taken up by the unmanned aerial vehicle as it takes-off and lands and hence the weight of the load is not applied to the unmanned aerial vehicle until it is sufficiently above the ground.

The tether may be releasably attached to the unmanned aerial vehicle and/or to the load. The tether may be remotely releasable, preferably via an electro-magnet. By having the tether releasably attachable to the unmanned aerial vehicle and or to the load, the load can be quickly attached or detached thereto. When the tether is remotely releasably attachable the unmanned aerial vehicle can lift and drop the load in remote situations without human interaction.

A method of operating an unmanned aerial vehicle is provided according to the present invention according to claim <NUM>.

This method the flight system to be used for the high precision manoeuvrability required for flight while the load system is used to provide lift for lifting a heavy load. This therefore allows the unmanned aerial vehicle to lift a heavy load while maintaining manoeuvrability during flight. Separating the first and second control systems allows the controller to effectively and efficiently provide additional thrust when necessary to lift the device separate to the flight control system.

The connection point may comprise a tether; and in the method: the step of attaching a load is carried out before the step of taking-off; and the load is attached to the tether such that the vehicle can fly around the load under slack in the tether before the weight of the load is applied to the connection point. The use of a tether allows the slack in the tether to be taken up by the unmanned aerial vehicle as it takes-off and lands and hence the weight of the load is not applied to the unmanned aerial vehicle until it is sufficiently above the ground.

Use of a load system comprising a first gas turbine propulsion system according to the present invention is provide according to claim <NUM>. The use is to provide thrust additional to the thrust provided by a flight system to lift a load attached to an unmanned aerial vehicle, the flight system thrust being used to manoeuvre the unmanned aerial vehicle.

This use the flight system to be used for the high precision manoeuvrability required for flight while the gas turbine propulsion system is used to provide lift for lifting a heavy load. This therefore allows the unmanned aerial vehicle to lift a heavy load while maintaining manoeuvrability during flight.

The present invention will now be described with respect to the following Figures in which:.

<FIG> shows an unmanned aerial vehicle <NUM> lifting a load <NUM>. The load <NUM> depicted in <FIG> is contained within a flexible bag, but an unmanned aerial vehicle <NUM> according to the present invention may be used for any type of load.

The unmanned aerial vehicle <NUM> comprises a frame <NUM>. The frame <NUM> may comprise a housing or form a part thereof. The frame <NUM> depicted in the Figures is generally cross shaped when viewed from above, but any suitable shape may be used. The frame <NUM> comprises a plurality of feet <NUM> for supporting the unmanned aerial vehicle <NUM> on the ground.

The unmanned aerial vehicle <NUM> further comprises a flight system <NUM> and a load system <NUM>. Each of the flight system <NUM> and the load system <NUM> are coupled to the frame <NUM>. A cargo area is provided on the unmanned aerial vehicle. The cargo area may, for example, be a container such as a cargo bay for receiving a load. The cargo area may be inside the frame/housing <NUM>. Alternatively, or in addition, the cargo area may comprise a connection point <NUM> to which a load can be coupled. The connection point <NUM> may be provided on an outer surface of the frame/housing <NUM>. The unmanned aerial vehicle <NUM> is provided with a connection point <NUM> provided on the frame <NUM>. The connection point <NUM> allows a load <NUM> to be attached to the unmanned aerial vehicle <NUM>.

The flight system <NUM> provides the thrust required to fly and manoeuvre the unmanned aerial vehicle <NUM> in an unloaded state. In particular, the flight system <NUM> comprises one or more rotor assembly <NUM>, preferably three or more. Each rotor assembly <NUM> comprises a flight rotor <NUM> and a corresponding electric motor <NUM>. The flight rotor <NUM> is attached to and driven by the electric motor <NUM>. The electric motor <NUM> is attached to the frame <NUM>. One or more sources of electrical power (not shown) are provided to drive the electric motors <NUM> and hence drive the rotors <NUM> to fly the unmanned aerial vehicle <NUM>. In particular, the sources of electrical power may be batteries, such as lithium-ion batteries.

In particular embodiments, an even number of rotor assemblies <NUM> are provided. Preferably, the unmanned aerial vehicle <NUM> comprises three, four, six or eight rotor assemblies <NUM>. These rotor assemblies <NUM> are preferably provided around an outer periphery of the unmanned aerial vehicle <NUM> as shown in <FIG>. Preferably, an outer perimeter of the unmanned aerial vehicle <NUM> is defined by the rotor assemblies <NUM>. The rotor assemblies <NUM> are preferably provided symmetrically around the unmanned aerial vehicle <NUM> to provide balanced forces in flight.

The rotor assemblies <NUM> define a thrust direction <NUM> in which air is directed to produce thrust for flight. A plane X may be defined passing through each one of the rotor assemblies <NUM>. This plane X is generally perpendicular to the ground plane when the unmanned aerial vehicle is sat on level ground for take-off. The thrust direction <NUM> of each rotor assembly <NUM> is generally vertically downwards (e.g. with respect to the unmanned aerial vehicle <NUM> when the feet are sat on level ground) or generally perpendicular to the plane X. The thrust direction <NUM> of each rotor assembly may have a deviation of up to and including <NUM> degrees from the perpendicular to the plane X. Preferably the deviation is between <NUM> and <NUM> degrees. While the thrust direction <NUM> of each rotor assembly <NUM> may deviate by up to <NUM> degrees, the net thrust direction of all the rotor assemblies <NUM> is preferably substantially perpendicular to the plane X.

A controller <NUM> is provided on the unmanned aerial vehicle <NUM> for controlling the flight system <NUM> to fly and manoeuvre the unmanned aerial vehicle <NUM>. While the controller <NUM> may be a single unit, it also may be a plurality of distributed units each of which contribute to the overall controller <NUM>.

The unmanned aerial vehicle <NUM> further comprises a load system <NUM>. This load system <NUM> is used to provide additional thrust in order to lift a load <NUM>. The load system <NUM> is preferably powered by combustion and so preferably comprises a combustion chamber. The load system <NUM> preferably comprises one or more gas turbine propulsion systems <NUM>. A gas turbine propulsion system <NUM> is a system for generating thrust which is driven by expanding hot gasses produced, for example, by burning a fuel.

These gas turbine propulsion systems <NUM> may comprise a ducted fan which produces the additional thrust by way of exhausting a jet of gas. In particular, the gas turbine propulsion system <NUM> may be a turbojet, turbofan or turboprop.

When a plurality of gas turbine propulsion systems <NUM> are provided, these are preferably arranged with an N-fold rotational symmetry in a plane generally perpendicular to the thrust direction <NUM>, where N is the number of gas turbine propulsion systems <NUM>. The plane generally perpendicular to the thrust direction <NUM> may be the plane X. For example, <FIG> shoes two gas turbine propulsion systems <NUM> and as shown in <FIG> these gas turbine propulsion systems <NUM> are arranged in a <NUM>-fold rotational symmetry.

One or more fuel storage tanks <NUM> are provided on the unmanned aerial vehicle <NUM> and are connected to the gas turbine propulsion systems <NUM>. Each fuel storage tank <NUM> stores combustible fuel (such as avtur (jet fuel)) for powering the gas turbine propulsion systems <NUM>. The fuel has a greater specific energy than the batteries of the flight system <NUM>. Jet fuel for example has a specific energy on the order of <NUM> MJ/kg. Therefore, the thrust to weight ratio provided by these gas turbine propulsion systems <NUM> is much greater than the rotor assemblies <NUM>.

Typically, gas turbine propulsion systems <NUM> cannot provide the fast and agile attitude control needed to fly the unmanned aerial vehicle <NUM> as the thrusts can only be varied by altering the fuel flow rate. In contrast, the rotor assembly <NUM>, because it is electric, can vary its thrust much quicker by sending a different electrical signal to the electric motor.

Each gas turbine propulsion system <NUM> may be provided within a radius defined by the rotor assemblies <NUM>. The radius may be defined by the innermost or outermost points of each rotor assembly <NUM>. Preferably, the fuel storage tanks <NUM> and cargo area are also provided within this radius. The cargo area is most preferably provided in a centre of the unmanned aerial vehicle <NUM>.

Preferably, each gas turbine propulsion system <NUM> does not overlap with the rotors <NUM>. This ensures that the air displaced by the rotors <NUM> does not subsequently contact any gas turbine propulsion systems <NUM>.

Operation of the unmanned aerial vehicle <NUM> will now be described with respect to <FIG>. <FIG> shows the unmanned aerial vehicle <NUM> at a first location with a load <NUM> to be moved at a spaced-apart second location. The unmanned aerial vehicle <NUM> carries out a take-off procedure in a first mode of operation as shown in <FIG>. In this mode of operation for take-off only the rotor assemblies <NUM> are actuated in order to generate a thrust <NUM> to allow the unmanned aerial vehicle <NUM> to take-off the ground and manoeuvre towards the load <NUM>. The lift thrusts generated by the respective propulsion systems of the unmanned aerial vehicle <NUM> are depicted by arrows in the direction of the expelled air. Of course, the direction of the force generated on the unmanned aerial vehicle <NUM> by this expelled air will be opposite to the direction of the arrows.

The unmanned aerial vehicle <NUM> is generally positioned above the load <NUM> as depicted in <FIG>. The tether <NUM> is connected to the load <NUM> via any conventional mechanism. In order to begin lifting the load <NUM> from the ground the gas turbine propulsion systems <NUM> are activated by the controller <NUM> to generate an additional lift <NUM> for lifting the load <NUM>. The controller <NUM> may comprise first and second control systems. The first control system controls the flight system <NUM> and the second control system controls the load system <NUM>.

This additional thrust <NUM> acts to counteract the weight L applied by the load <NUM> onto the unmanned aerial vehicle <NUM>. With this load L counteracted by the thrust from the turbine propulsion system <NUM> the rotor assemblies <NUM> can continue to fly and manoeuvre the vehicle <NUM> as their contribution is not required to lift the load <NUM>. <FIG> shows the unmanned aerial vehicle <NUM> beginning to lift the load <NUM> from the ground.

The load <NUM> can then be transported to a further location as shown in <FIG> and detached from the tether <NUM> via any conventional means. Once the load <NUM> has been detached from the unmanned aerial vehicle <NUM> the turbine propulsion system <NUM> may be deactivated.

The rotor assemblies <NUM> may fly the unmanned aerial vehicle <NUM> back to a base position as shown in <FIG>.

In this manner, the present invention allows an unmanned aerial vehicle <NUM> to be used to lift and transport heavy loads while still maintaining the manoeuvrability of a conventional unmanned aerial vehicle.

The unmanned aerial vehicle comprises a load sensor (for example, as part of the connection point <NUM>) in communication with the controller <NUM>. The load sensor is configured to provide a signal indicative of the weight applied by the load <NUM> attached to the connection point <NUM>. The controller is then configured to control the load system <NUM> and hence the gas turbine propulsion system <NUM> in response to the signal indicative of the weight L applied to the connection point <NUM>. In this manner, the controller <NUM> may be used in a closed-loop control system to balance the weight L applied to connection point <NUM> with the force provided by the thrust of the gas turbine propulsion systems <NUM>.

In a preferred embodiment, the second control system may vary the throttle of the gas turbine propulsion systems <NUM> based on the sensed load to balance the load and thrust.

In preferred embodiments the gas turbine propulsion systems <NUM> may be angled with respect to the thrust direction of the flight rotors <NUM>. This angling of the gas turbine propulsion systems <NUM> may be symmetrical so as to ensure that each gas turbine propulsion system <NUM> is arranged to counteract one another and hence not to contribute to movement in the horizontal direction. That is, the net thrust vector is substantially only in the vertical direction, perpendicular to the plane X. This can be used to enhance the stability of the unmanned aerial vehicle <NUM>. Preferably, the gas turbine propulsion systems <NUM> may each be angled by up to <NUM> degrees from the perpendicular to the plane X (that is, they may diverge from the vertical direction by up to <NUM> degrees). Preferably the angle may be between <NUM> and <NUM> degrees. This directs the jet plume(s) away from the load <NUM>.

The tether <NUM> of the present invention allows the unmanned aerial vehicle <NUM> to fly around the load <NUM> before the weight L of the load <NUM> is applied to the connection point <NUM>. In particular, this is useful for instances where the unmanned aerial vehicle <NUM> may be attached to load <NUM> prior to take-off or may be detached after landing. In such embodiments the unmanned aerial vehicle <NUM> is able to take-off and/or land without the weight L of the load <NUM> being applied to the connection point <NUM> thanks to a slack in the tether <NUM>. As this weight L is not being applied to the connection point <NUM> this unmanned aerial vehicle <NUM> may land and/or take-off using only the rotor assemblies <NUM> which, as discussed above, are much easier for fine control.

Claim 1:
An unmanned aerial vehicle (<NUM>) comprising:
a flight system (<NUM>) for producing thrust to manoeuvre the unmanned aerial vehicle (<NUM>) comprising:
one or more flight rotors (<NUM>) defining a plane (X) passing through each flight rotor (<NUM>) and a thrust direction (<NUM>) generally perpendicular to the plane (X); and
one or more electric motors (<NUM>) for driving the one or more flight rotors (<NUM>); a cargo area for coupling to or receiving a load (<NUM>);
a load system (<NUM>) for providing thrust additional to the thrust provided by the flight system (<NUM>) to thereby lift a load (<NUM>) attached to a connection point and coupled to or received in the cargo area, the load system (<NUM>) comprising:
a first gas turbine propulsion system (<NUM>);
a controller (<NUM>) configured to control the flight system (<NUM>) and load system (<NUM>); and
a load sensor in communication with the controller (<NUM>), the load sensor being configured to provide a signal indicative of a weight applied by the load (<NUM>) attached to the connection point, wherein the controller (<NUM>) is configured to control the load system (<NUM>) in response to the signal.