Field of the Invention

The present invention relates generally to an aerial drone and particularly, although not exclusively, to a hybrid VTOL drone.

Background of the Invention

Flight endurance and ability to fly in adverse weather are two problems that hamper drones and unmanned aerial vehicles (UAVs). Maximum average flight times of multirotor drones are less than 1 hour and often no more than 20 minutes. High winds are further detrimental to these flight times with drones having to ‘fight’ the wind to stay in the air. Hybrid drones are the current industry solution to providing a drone suitable for windy conditions, by combining the Vertical Take-off and Landing (VTOL) capabilities of a drone with the long- range flight performance of a plane. This can increase flight times and range of drones. Current hybrids comprise a fixed wing and often transition between hovering modes and fixed wing flight, having separate motors and flight structures used independently in each flight mode. This means that there are often redundant components in a flight mode, leading to a decrease in flight efficiency. Traditional quadcopter drones are popular due to their ease of use, manoeuvrability, vertical take-off and landing and ability to hover. Current hybrids therefore sacrifice some of those benefits in order to provide more stability in the air, as they are not able to hover as well as the most widely adopted multirotor crafts and are less efficient at flying long distances than normal fixed wing planes. Current hybrid designs are not capable of making use of wind currents to stay in the air and are hampered by high winds. Existing designs use motor lift to hover, reducing the efficiency of the drone. There is therefore a requirement to provide a hybrid VTOL drone with increased stability in high wind conditions without sacrificing manoeuvrability, vertical take-off and landing, and ability to hover, alongside the overall drone efficiency.

The present invention seeks to provide an improved hybrid VTOL drone.

Summary of the Invention

An aspect of the present invention provides a hybrid VTOL drone comprising a minimum of four propellers, fixedly mounted and disposed onto a frame that includes a pitch shaft, and a wing rotatably mounted to the pitch shaft, wherein the wing is rotatable around a pitch axis along the pitch shaft. The pitch shaft may be part of the frame.

A further aspect provides a hybrid VTOL drone comprising: a pitch shaft; at least four propeller assemblies, each propeller assembly fixedly mounted to and disposed on the pitch shaft; and a wing rotatably mounted to the pitch shaft; wherein the wing is rotatable around a pitch axis along the pitch shaft.

The drone may comprise at least two wings. Each wing may be separately actuatable with respect to the other.

The pitch shaft may comprise at least two axially aligned shafts.

The drone may comprise at least one wing motor for rotating the wing around the pitch axis of the pitch shaft. The motor/s therefore drive the rotation of the wing around the pitch shaft.

Wing motors can be positioned anywhere, as part of either the frame or the wing, provided they can actuate a rotation of the wing, around the pitch axis, relative to the rest of the drone. The motors can drive this rotation directly or through any sort of mechanical linkage.

A wing motor may be fixedly mounted to and attached to either end of the pitch shaft or attached to either end of the pitch shaft.

The drone may comprise four propeller assemblies, arranged in pairs, each pair being fixedly mounted to and disposed at either end of the pitch shaft. Each propeller motor drives its respective propeller.

The propeller assemblies may each additionally comprise at least one battery.

The pitch shaft and propeller assemblies may be part of a frame. The frame may additionally comprise a flight payload, flight controllers, flight avionics and batteries

The frame may comprise several distinct sections, each section having electronic and mechanical components required for flight such as onboard sensors for measuring the direction and speed of airflow around the drone, using these as inputs in the control system controlling motor speeds, propeller thrust, wing angles and any control surfaces.

The flight payload may be fixedly attached to the pitch shaft.

The flight controllers may be fixedly attached to the pitch shaft

The wing may comprise an aerofoil cross section.

In some embodiments the angle of attack of the wing can be varied.

Wings may include additional control surfaces such as ailerons with additional motors driving these control surfaces.

In some embodiments the drone has two flying modes: ‘bird’ configuration in which the motor force and lift force are parallel, and ‘plane’ configuration in which the motor force is generally perpendicular to the lift force.

A plane on which the pitch shaft and propeller assemblies lie may be generally horizontal in ‘bird’ configuration, and the plane on which the pitch shaft and propeller assemblies lie may be generally vertical in ‘plane’ configuration.

‘Bird’ and ‘plane’ mode may be extreme positions, and any transitional phase between these two modes where the motor/s are providing lift and forward thrust and the wing/s are providing lift is also a valid form of flight.

Some aspects and embodiments include means for flight stability and/or control. For example rotational flight stability in roll, pitch and yaw may be provided through the differential control of multiple (e.g. four) propeller motors.

The drone may, for example, be capable of independently controlling the speed and thrust of each offour or more propellers, the angle of the wings and the angle of additional control surfaces independently of one another.

Some embodiments therefore provide the combination of having multiple motors providing stability together with the separate control of the wing angle. Multiple (e.g. four) propellers together can provide rotational moments in different (e.g. any) orientation of the craft, meaning that additional control surfaces are not required (however, they may also be included). This also means that there is no coupling between stability and wing angle allowing the wing to be controlled freely to optimise lift.

Some embodiments may include a tail with additional lifting surfaces such as a vertical or horizontal tail.

These lifting surfaces may include additional control surfaces such as elevators or rudders and additional motors to control these surfaces.

These surfaces may be used to improve the stability of the drone.

The tail may also be used to decrease the amount of torque required by the wing motors to rotate the wing around the pitch shaft.

In some embodiments the angle of the wing of the drone may be solely controlled by changing the angle control surfaces such as an elevator attached to the tail. In these embodiments additional motors to move the wing may not be required.

In some embodiments components such as flight controllers, sensors, payloads or batteries may be attached to the wing.

A further aspect provides a drone comprising a pitch shaft, and a wing rotatably mounted to the pitch shaft, the wing is rotatable around a pitch axis along the pitch shaft.

The drone may be a hybrid drone (for example a multirotor unmanned aerial vehicle having a plurality of energy sources to power its propulsion).

The drone may be configured as a VTOL UAV.

The drone may have (only) four propellers, arranged in two pairs, each pair is mounted to and disposed at or towards either end of the pitch shaft.

Each propeller may have, for example, two, three, four or more blades. The present invention also provides a delivery drone or a delivery drone system comprising a drone as described herein.

Different aspects and embodiments of the invention may be used separately or together.

Further particular and preferred aspects of the present invention are set out in the accompanying independent and dependent claims. Features of the dependent claims may be combined with the features of the independent claims as appropriate, and in combination other than those explicitly set out in the claims. Each aspect can be carried out independently of the other aspects or in combination with one or more of the other aspects.

Brief Description of the Drawings

The present invention will now be more particularly described, by way of example, with reference to the accompanying drawings, in which:

Figure 1 shows a top view of a drone formed according to an embodiment of the present invention;

Figure 2 shows a front view of the drone;

Figure 3A show a side view of the drone in ‘bird’ configuration;

Figure 3B shows a side view of the drone during the transition between ‘bird’ and ‘plane’ configuration;

Figure 3C shows a side view of the drone in ‘plane’ configuration;

Figure 4A shows the forces on the drone in ‘bird’ configuration;

Figure 4B shows the forces on the drone in ‘plane’ configuration;

Figure 5 is a graph of the expected flight time against the relative wind speed.

Figure 6 shows the drone in relation to its axes of rotation;

Figure 7 shows a top view of a drone formed according to a further embodiment of the invention and depicted in a ‘bird’ configuration;

Figure 8 shows a side view of embodiment of Figure 7 in a ‘plane’ configuration; and Figures 9A and 9B are side views of the drone of Figures 7 and 8 in ‘plane’ configuration showing additional forces and moments.

Description The example embodiments are described in sufficient detail to enable those of ordinary skill in the art to embody and implement the systems and processes herein described. It is important to understand that embodiments can be provided in many alternate forms and should not be construed as limited to the examples set forth herein.

Accordingly, while embodiments can be modified in various ways and take on various alternative forms, specific embodiments thereof are shown in the drawings and described in detail below as examples. There is no intent to limit to the particular forms disclosed. On the contrary, all modifications, equivalents, and alternatives falling within the scope of the appended claims should be included. Elements of the example embodiments are consistently denoted by the same reference numerals throughout the drawings and detailed description where appropriate.

In the following description, all orientational terms, such as upper, lower, radially and axially, are used in relation to the drawings and should not be interpreted as limiting on the invention.

Unless otherwise defined, all terms (including technical and scientific terms) used herein are to be interpreted as is customary in the art. It will be further understood that terms in common usage should also be interpreted as is customary in the relevant art and not in an idealised or overly formal sense unless expressly so defined herein.

Referring now to the drawings, wherein like reference numbers are used to designate like elements throughout the various views, several embodiments of the present invention are further described. The figures are not necessarily drawn to scale, and in some instances the drawings may have been exaggerated or simplified for illustrative purposes only. One of ordinary skill in the art will appreciate the many possible applications and variations of the present invention based on the following examples of possible embodiments of the present invention.

A drone formed according to an embodiment of the invention is shown in Figure 1 and Figure 2. The drone 10 comprises four propeller assemblies 32a, 32b, 32c, 32d. Each assembly comprised of a propeller driven by an electric motor. The speed of each motor/ propeller can be varied independently. Two frame sections 34a, 34b house the four propeller assemblies 32a, 32b, 32c, 32d. Each frame section 34a, 34b additionally houses a battery. A third frame section 22 houses a flight controller, sensors and a payload. There is a pitch shaft 20 that is rigidly attached to the three frame section 34a, 34b, 22. The three frame sections and the pitch shaft 34a, 34b, 22, 20 make up a single rigid frame. In this embodiment the pitch shaft 20 is hollow to accommodate wiring that connects the electronic components in each frame section 34a, 34b, 22.

The frame may comprise several distinct sections. Each frame section may house propeller assemblies, batteries, flight avionics, flight controllers, flight payloads, the pitch shaft or any other electronic or mechanical component needed for the drone to fly provided the sections are rigidly joined to each other.

Wings 40a, 40b are rotatably mounted on the pitch shaft 20 and driven by their respective wing motors 42a, 42b. The wing motors induce a rotation of the wing around the pitch axis 50 relative to the frame, changing the angle of attack of the wing. This rotation can be up to 360 degrees around the pitch axis and can be controlled independently from the pitch orientation of the frame. In this embodiment, wing motors 42a, 42b are mounted at either end of the pitch shaft 20. The wings 40a, 40b have an aerofoil section so as to provide lift when air flows over the wings 40a, 40b.

The pitch shaft 20, payload body 22 and propeller assemblies are all fixedly mounted on the pitch shaft 20 along a single plane. The plane on which these components sit is rotatable around a pitch axis 50 of the drone, the pitch axis 50 being defined as along the pitch shaft 20. In this configuration propellers 32a and 32d spin in the opposite direction of propellers 32b and 32c.

Rotation of the drone around either the pitch 50, roll 51 or yaw 52 axis is achieved by differential control of the speed of the four propellers. The axes of rotation are shown in Figure 6. Rotation around the pitch axis 50 is achieved by increasing the speed of propellers 32a and 32c whilst decreasing 32b and 32d (or vice versa). Rotation around the roll axis 51 is achieved by increasing the speed of propellers 32a and 32b whilst decreasing 32c and 32d (or vice versa). Rotation around the yaw axis 52 is achieved by increasing the speed of propellers 32a and 32d whilst decreasing 32b and 32c (or vice versa). The lift produced by the wings 40a, 40b can be controlled by changing the angle of attack of each wing using motors 42a, 42b. Differentially changing the lift produced by each wing 40a, 40b in this manner can be used to rotate the drone around the roll axis 51 .

The angle of attack can be varied to adapt to different wind speeds, allowing for improved stability of the drone in high wind conditions.

The drone may have a flight controller capable of controlling each of the speed of each propeller assembly 32a, 32b, 32c, 32d, the angle of any wings 40a, 40b and the angle of any additional control surfaces completely independently of each other and use the resultant forces produced to keep the drone 10 stable in the air.

Lift, defined as the force opposing any gravitational forces acting on the drone, can be produced by either the propeller assemblies 32a, 32b, 32c, 32d or the wings 40a, 40b or any combination of these.

The angle of the plane can be adjusted so that the drone 10 can transition between a ‘bird’ configuration, and a ‘plane’ configuration, as shown in Figures 3A, 3B, 3C and Figures 4A, 4B.

In ‘bird’ configuration, as shown in Figure 4A, the drone is hovering and lift is being provided by the propeller assemblies 32a, 32b, 32c, 32d and the wings 40a, 40b. The plane of the propeller assemblies is substantially horizontal with respect to the ground, and the lift force is obtained from propeller thrust A and from the wing lift B. Movement of air C over the wings 40a, 40b provides lift force due to the aerofoil design of the wing.

In ‘plane’ configuration, as shown in Figure 4B, the lift is being provided by the wing lift B alone. The plane of the propeller assemblies has been rotated around the pitch shaft 20 such that the plane is substantially vertical with respect to the ground and the wings 40a, 40b. The propeller thrust A is directed in the direction of travel, substantially perpendicular to the lift force.

It should be noted that, at least in this embodiment, the drone is not limited to just flying in 'bird' or 'plane' mode; these are just extreme positions. Any transitional phase between these two modes where the motors are providing lift and forward thrust and the wings are providing lift is also a valid form of flight. 'Bird' and 'plane' mode are therefore provided for as examples rather than fixed modes in this embodiment.

In ‘bird’ configuration, more lift is obtained from the wing, therefore requiring less thrust from the propellers, improving efficiency and flight time. In ‘plane’ configuration, it allows the propeller thrust to be solely used for forward motion, as lift force is provided by the wing, again improving efficiency. The wing allows for more steady hovering in high wind conditions.

Figure 5 shows a graph of expected flight time vs relative wind speed. The graph shows that the flight time is greatly increased from the presence of the wing, and that the drone has a significantly increased flight time in higher wind speeds than in lower wind speeds. Due to the aerofoil shaped wing, higher wind speeds allow for greater lift generation.

In this embodiment the wing 40 is split into two moveable sections 40a, 40b. Further embodiments may comprise additional, independently controllable sections.

The invention has been shown to improve flight times to 6 to 8 hours using battery power alone, and capable of flying in wind speeds up to 50mph.

The combination of the wing and the four motors allows for vertical take-off and landing and efficient hovering.

Figures 7 and 8 show a drone formed according to another embodiment of the invention.

In this embodiment the wing motors 142a, 142b are rigidly fixed to the wings 140a, 140b and each comprises an additional belt and pulley system 173a, 173b that transmits the torque from the motors to the pitch shaft 120.

Each wing 140a, 140b may also have an additional tail section 170a, 170b rigidly attached to it. Each tail section can include a horizontal stabiliser section 171a, 171 b that may have an aerofoil cross section. An additional actuated control surface commonly known as an elevator, 172a 172b, may be attached to the horizontal stabiliser to change the lift characteristics of the tail section during flight. The purpose of the tail section is to reduce any unwanted pitching moments that are produced by the wing during flight and so reducing the torque that the wing motors, 142a, 142b have to produce. By controlling the angle of the elevator 172a, 172b with respect to the horizontal stabiliser, the tail section can produce either a positive or negative pitching moment around the pitch shaft 120. As such the tail section can be seen as having a similar role to wing motors 142a, 142b and can be used to either supplement the torque of the wing motors or replace the wing motors entirely.

Some embodiments may not include wing motors 142a, 142b and rely solely on the control of the elevator surface 172a, 172b to control the angle of the wings 140a, 140b relative to the pitch shaft and the rest of the rigid frame, 120, 122, 134a, 134b.

In some embodiments an additional vertical stabiliser or similar lifting surfaces may be added to the tail section to aid the stability of the drone.

Reference numerals 180a and 180b show the force produced by the propeller assemblies 132a, 132b, 132c and 132d. 180c shows the force produced by the wing sections 140a and 140b and 180d shows the force produced by the horizontal stabiliser and elevator 171a, 171 b, 172a, 172b.

Figure 9 shows how the elevator, 172a, angle may be changed to change the direction of the force 191a, 191 b that it produces and therefore the direction of the pitching moment, 190a, 190b around the pitch shaft 120. Figure 9A shows the elevator 172a in an ‘downward’ position and Figure 9B in an ‘upward’ position.

Although illustrative embodiments and examples of the invention have been disclosed in detail herein, with reference to the accompanying drawings, it is to be understood that the invention is not limited to the precise embodiment and examples shown and/or described and that various changes and modifications can be effected therein by one skilled in the art without departing from the scope of the invention as defined by the appended claims.