Unmanned aerial system

Abstract

An unmanned aerial system (UAS) (10) includes a body (20), a first forward wing (40) and a second forward wing (50) extending away from opposing sides of the body (20); and a first rear wing (60) and a second rear wing (70) extending away from opposing sides of the body (20). The (UAS) (10) includes a motor (80) having a rotor (90) supported by each wing (40, 50, 60, 70). Each wing (40, 50, 60, 70) is twisted about a longitudinally extending axis between a proximal region and a distal region, such that a chord line (XX) taken through each wing (40, 50, 60, 70) at a location between the proximal region and the distal region becomes closer to parallel with an axis of rotation (YY) of the rotor (90) the closer the chord line is located relative to the rotor (90).

Description

Unmanned aerial systemField of the invention

[0001] The present invention relates to an unmanned aerial system (UASs) and more specifically to vertical take-off and landing (VTOL) drones. VTOL drones or UASs can take off and landing vertically, which provides significant operational flexibility in environments where traditional runway-based take-offs and landings are not feasible.Background of the Invention

[0002] Drones are increasingly finding commercial applications in fields such as photography and videography, delivery, reconnaissance, law enforcement, agriculture, military, search and rescue, conservation, infrastructure and maintenance, and other diverse fields.

[0003] Drones including multi-rotor and hybrid rotor-fixed wing designs, have gained prominence for their ability to perform vertical take-off and landing operations. This capability is advantageous for applications in urban environments, rugged terrain, and confined spaces. VTOL capability enables the drone to readily depart and return to the same point, regardless of ground conditions.

[0004] However, conventional VTOL drones face some inherent limitations, particularly concerning their operational range and efficiency.

[0005] Beyond the take-off stage, the rotational plane of the rotors needs to be tilted to achieve forward thrust and there are many ways to achieve that.

[0006] Many varieties of VTOL drones utilise fixed motor mounts. Whilst such geometry assists with vertical take-off and landing, flying at higher speeds with such configurations is generally less efficient.

[0007] Some VTOL drones rely on separate propulsion systems for vertical and forward flight. For example, a multi-rotor drone uses multiple rotors for vertical lift but switches to fixed wings or tiltrotors for forward flight.

[0008] Typical multi rotor UASs require increased motor power during high-speed flight to maintain lift and height.

[0009] Some conventional fixed rotor VTOL drones suffer from aerodynamic “blocking” in which the lift force generated by each rotor may be inhibited by the structure of the drone body. This effect has adverse implications on range and power consumption.Summary of the invention

[0010] In a first aspect, the present invention provides an unmanned aerial system (UAS) comprising: a body; a first forward wing and a second forward wing extending away from opposing sides of the body; and a first rear wing and a second rear wing extending away from opposing sides of the body; each wing supporting a motor having a rotor; wherein each wing is twisted about a longitudinally extending axis between a proximal region and a distal region, such that a chord line taken through each wing at a location between the proximal region and the distal region becomes closer to parallel with an axis of rotation of the rotor the closer the chord line is located relative to the rotor.

[0011] In a second aspect, the present invention provides an unmanned aerial system (UAS) comprising: a body; a first forward wing and a second forward wing extending away from opposing sides of the body; and a first rear wing and a second rear wing extending away from opposing sides of the body; a motor having a rotor mounted to each wing; wherein each wing is twisted about a longitudinally extending axis between a proximal region and a distal region, such that a trailing edge of eachwing is more downwardly inclined in the vicinity of the distal region near a wing tip than at the proximal region adjacent to the body.

[0012] Each wing preferably has a cross-sectional profile in the form of an aerofoil.

[0013] Preferably the first forward wing and the first rear wing are located on the same side of the body and are connected by a first connection member, and the second forward wing and the second rear wing are located on the same side of the body and are connected by a second connection member.

[0014] The connection member is preferably generally planar and extends parallel to the axis of rotation.

[0015] Each motor is preferably located at or near a distal wing tip.

[0016] Adjacent to the rear wings, each of the first and second connection members preferably have an increased thickness, in a direction extending parallel with the axis of rotation.

[0017] The first and second forward wings, the first and second rear wings and the first and second connection members preferably define a generally rectangular perimeter structure of the UAS.

[0018] At the proximal regional of each wing, adjacent to the body, the chord line is close to parallel to a direction of flight in a forward flight mode, but inclined by a local angle of attack of an aerofoil of the wing.

[0019] Each wing preferably includes at least one internal passage for housing at least one motor control and / or power cable.

[0020] Each wing preferably includes at least one gurney flap located on an underside surface adjacent to a trailing edge.

[0021] In a third aspect, the present invention provides an unmanned aerial system (UAS) comprising: a body; a first forward wing and a second forward wing extending away from opposing sides of the body; and a first rear wing and a second rear wing extending away from opposing sides of the body;a motor having a rotor mounted to each wing; wherein each wing is twisted about a longitudinally extending axis between a proximal region and a distal region, such that a surface area of each wing, when viewed in a plane that is perpendicular to an axis of rotation of the respective rotor, is reduced beneath a swept area of said rotor.

[0022] In a fourth aspect, the present invention provides a method of operating an unmanned aerial system (UAS), the UAS having a body; a first forward wing and a second forward wing extending away from opposing sides of the body; and a first rear wing and a second rear wing extending away from opposing sides of the body; a motor having a rotor mounted to each wing; wherein each wing is twisted about a longitudinally extending axis between a proximal region and a distal region, such that a chord line taken through each wing becomes closer to parallel with an axis of rotation of the rotor the closer the chord line is to the rotor; the method including the step of operating the rear rotors at a faster rotational speed relative to the forward rotors to raise a rear end of the body so that each wing is aerodynamically generating lift in a region adjacent to the body.

[0023] Preferably in forward flight the body is inclined so that a chord line of each wing at a proximal location adjacent to the body is offset relative to a direction of flight by a local angle of attack of the wing.Brief description of the drawings

[0024] The invention will now be described with reference to the accompanying drawings as follows:

[0025] Figure 1 is a top perspective view of an unmanned aerial system (UAS) according to the invention;

[0026] Figure 2 is a top view of the unmanned aerial system of Figure 1 ;

[0027] Figure 3 is a side view of the unmanned aerial system of Figure 1 ;

[0028] Figure 4 is a perspective view of a wing and motor housing of the unmanned aerial system of Figure 1 ;

[0029] Figure 5 is a side view of the wing and motor housing of Figure 4;

[0030] Figure 6 is an end view of the wing and motor housing of Figure 4;

[0031] Figure 7 is a top view of the wing and motor housing of Figure 4;

[0032] Figure 8 is a further perspective view of the wing and motor housing of the unmanned aerial system of Figure 1 ;

[0033] Figure 9 is a first cross-sectional proximal end view of the wing of the unmanned aerial system; and

[0034] Figure 10 is a second, opposing cross-sectional distal end view of the wing of Figure 9.Detailed description of preferred embodiments

[0035] An unmanned aerial system (UAS) 10 is disclosed. The UAS includes a central body 20 which houses an onboard control system 30 having a processor, battery, and remote signal communication device for communication with a remote controller or other control system.

[0036] As shown In Figure 1, the UAS 10 includes a first forward wing 40 and a second forward wing 50. The forward wings 40, 50 each extend away from laterally opposing sides of the central body 20.

[0037] The UAS 10 also includes a first rear wing 60 and a second rear wing 70 extending away from opposing sides of the body 20. The UAS 10 has a static, nonmoving, non-articulating aerostructure.

[0038] In the embodiment depicted, the wings 40, 50, 60, 70 each intersect and extend away from body 20. However, it will be appreciated that in an alternative arrangement, the forward wings 40, 50 and / or the rear wings 60, 70 may be mounted onspars or other support structures to pass centrally over or under the body 20, to extend the aerodynamic length of each wing 40, 50, 60, 70.

[0039] At least one motor 80 having a rotor 90 is mounted to each wing 40, 50, 60, 70. In the embodiment depicted in the drawings, there are four motors 80, mounted at or near wing tips. However, it will be appreciated that each wing 40, 50, 60, 70 may be provided with more than one motor 80.

[0040] In a preferred embodiment, each rotor 90 has two diametrically opposed rotor blades. However, it will be appreciated that other arrangements such as three or four rotor blades may be embodied.

[0041] As shown in Figure 1 , each wing 40, 50, 60, 70 is twisted about a longitudinally extending axis between a proximal region (adjacent to the body 20) and a distal region (furthest from the body 20), such that a chord line XX (for example as depicted in figure 10) taken through each wing 40, 50, 60, 70 becomes closer to parallel with an axis of rotation YY of the rotor 90 the closer the chord line is to the motor 80.

[0042] A chord line is a notional straight line drawn between the leading and trailing edges of the aerofoil.

[0043] The twisting occurs over a twist zone 85. In the embodiment depicted, the twist zone extends along most of the length of each wing 40, 50, 60, 70. The twist zone 85 may be defined by a helical arrangement, such as a twisted ribbon, having a long pitch, such that the degree of twisting between the proximal and distal ends of the wing 40, 50, 60, 70 is less than or equal to 90 degrees, and more preferably less than 45 degrees from the assumed angle of the body in forward flight.

[0044] This can be seen in the top view of Figure 2, in which the width of each wing 40, 50, 60, 70 decreases towards the distal end, where the motor is located. As a result of the wing twist and the reduction in width of the wing 40, 50, 60, 70 when viewed at the distal tip, the wing 40, 50, 60, 70 has less surface area when viewed in a plane that extends parallel to the swept surface area of the rotor 90. Aerodynamically this reduces the amount of blocking that occurs as a result of the wings 40, 50, 60, 70. This is because the wings have a reduced surface area (in a plane extending perpendicular to the rotation axis) in the vicinity of the distal wing tips.

[0045] The twist in the wings 40, 50, 60, 70 may be an even, linear twist, about a longitudinal axis. Alternatively the twist may be more pronounced at a certain region of the wings 40, 50, 60, 70. For example, the twist may occur predominantly in the distal region of each wing 40, 50, 60, 70, near the wing tip.

[0046] In one embodiment, the twist may occur over a shorter twist zone 85, defined by a more pronounced twist region, so that the wings 40, 50, 60, 70 transition quickly from a proximal arrangement to a distal arrangement, in which the chord lines of the aerofoils are angularly offset relative to each other. For example, the twist zone may occur just outside of a swept area of the rotor.

[0047] As shown in figure 8 to 10, each wing 40, 50, 60, 70 has a cross-sectional profile in the form of an aerofoil. Figure 9 depicts one of the wings 40, 50, 60, 70 from the proximal end, whilst Figure 10 depicts the wing 40, 50, 60, 70 from the distal end. As shown, the trailing edge of the aerofoil is downwardly inclined at around 50 degrees, at or adjacent to the body 20, and significantly downwardly inclined at or near the wing tip.

[0048] As depicted in Figure 1, the first forward wing 40 and the first rear wing 60 are located on the same side of the body 20 and are connected by a first connection member 100, and the second forward wing 50 and the second rear wing 70 are located on the same side of the body 20 and are connected by a second connection member 110.

[0049] As can be seen in the top view of Figure 2, the connection members 100, 110 are generally planar and extends parallel to the axis of rotation. The thin profile of the connection members 100, 110 in the vertical planes results in minimal aerodynamic blocking of the rotors 90. However, the connection member 100, 110 provide improved structural rigidity.

[0050] In one embodiment, not depicted, the first 50% of connection members 100, 110 has a perforated structure to alleviate directional instability at high side-angles.

[0051] As shown in the drawings, the UAS 10 has four motors 80 and rotors 90 with each motor 80 being located at or near a distal wing tip. However, it will be appreciated that the UAS 10 could have a different motor and rotor arrangement, forexample a group of 2, 3 or 4 motors 80 and rotors 90 being located at each wing tip.Another embodiment may include additional motors 80 and rotors 90 being located on the body 20.

[0052] As shown in Figure 1 , adjacent to the rear wings 60, 70, each of the first and second connection members 100, 110 has a region of increased thickness 105, in a direction extending parallel with the axis of rotation. The feature serves 2 purposes (1) to provide planar surfaces that serve as a landing platform to stabilise the aircraft on the ground and (2) increase of surface area at the rear promotes directional stability.

[0053] As shown in Figure 2, the first and second forward wings 40, 50, the first and second rear wings 60, 70 and the first and second connection members 100, 110 define a generally rectangular perimeter structure of the UAS 10.

[0054] At the proximal regional of each wing 40, 50, 60, 70, adjacent to the body 20, the chord line of the wing aerofoil is generally parallel to a direction of flight in a forward flight mode.

[0055] As shown in Figures 8 to 10, each wing 40, 50, 60, 70includes at least one internal passage 120 for housing at least one motor control and / or power cable, to couple the motor 80 to the control system 30 in the body 20. The wings 40, 50, 60, 70 are predominantly hollow to minimise their mass.

[0056] As shown in the embodiment of Figures 4, 5, and 6, each wing 40, 50, 60, 70 includes at least one surface formation intended to alter the aerodynamic performance of the wing, such as a gurney flap 130 which is located on an underside surface adjacent to a trailing edge. The gurney flap 130 may extend along the complete length of the wing 40, 50, 60, 70, or it may extend along only a central portion of the length of the wing, as depicted in Figure 5. The gurney flap 130 may also serve the purpose of providing an internal channel or conduit to run cable from the body 20 to the motors 80.

[0057] As shown in Figure 4, each motor 80 is mounted on a mounting plate 85, which is an integrally formed part of the wing 40, 50, 60, 70. However, the mounting plate 85 may alternatively be separately formed, or alternatively it may be defined by end components of the first and second connection members 100, 110.

[0058] The operation of the UAS will now be described. During vertical take-off and landing, the UAS sits in a generally horizontal configuration, similar to that shown in Figure 3. In that mode of operation, the rotors 90 on the forward wings 40, 50 and the rotors 90 on the rear wings 60, 70 are positioned on a common horizontal plane.Typically during take-off and landing, and other vertical flight modes, all rotos 90 are generally operated at the same rotational speed.

[0059] When the UAS 10 is transitioned to a forward flight mode, forward rotors 90 are rotated at a lower rotational speed relative to the rear rotors 90. This has the effect of tilting the body 20, so that the nose sits vertically lower than the tail. The body 20 is tilted around 45 degrees at its cruise point.

[0060] Once the body 20 tilts downwards, the unmanned aerial system (UAS) 10 starts to move forward due to the tilt of the rotational plane of propellers 90, which will generate forward thrust. This movement will result in relative airspeed experienced by the airframe. The relative airspeed will influence the lift generated by the propellers, which results in lift contribution called translational lift. This will slightly reduce the power consumption. Due to the presence of the optimised wings 40, 50, 60, 70, the UAS 10 amplifies the translational lift effect and generates further wing-borne lift. It also allows the UAS 10 to be optimised for greater forward speed than a counterpart without wings.

[0061] In this forward flight or cruise position, the body is orientated so that each wing 40, 50, 60, 70 at a proximal location adjacent to the body 20 is slightly inclined relative to a direction of flight in the forward flight mode, that difference being defined by the angle of attack of the aerofoil. This enables the wings 40, 50, 60, 70, to generate more aerodynamic lift due to reduction in local angle-of-attack near the body, delaying stall and laminar bubble separation, so that the lift forces acting on the UAS are not purely provided by the rotors 90.

[0062] The UAS 10 uses lift from aerodynamic surfaces to support generation of lift during high-speed flight.

[0063] The twisting of the wings 40, 50, 60, 70 reduces blockage effects during stationary hover, however the wings 40, 50, 60, 70 are still efficient in cruise due to the large effect on the airflow due to rotor thrust.

[0064] The body 20 is also aerodynamically streamlined to minimise drag losses and also generate additional lift. The is in particular assisted by the shape of the body 20, which has an aerofoil profile.

[0065] The UAS 10 provides equivalent performance to a hover optimised multirotor during static flight, and equivalent (or near) performance to a fixed wing optimised UAS during cruise (high speed) flight.

[0066] Advantageously, the UAS 10 outperforms typically multirotor designs in high speed flight without ceding performance in stationary hover flight.

[0067] Advantageously, the UAS 10 has improved structural and performance benefits over UASs with dedicated wing surfaces or full transition into wing-borne flight.

[0068] Advantageously, the UAS 10 can fly faster and longer, beating both performance and endurance of competitive products and without any other modifications to the configuration or flight controls.

[0069] Where it is used, the word “comprising” is to be understood in its “open” sense, that is, in the sense of “including”, and thus not limited to its “closed” sense, that is the sense of “consisting only of’. A corresponding meaning is to be attributed to the corresponding words “comprise”, “comprised” and “comprises” where they appear.

Claims

Claims:

1. An unmanned aerial system (UAS) comprising: a body; a first forward wing and a second forward wing extending away from opposing sides of the body; and a first rear wing and a second rear wing extending away from opposing sides of the body; each wing supporting a motor having a rotor; wherein each wing is twisted about a longitudinally extending axis between a proximal region and a distal region, such that a chord line taken through each wing at a location between the proximal region and the distal region becomes closer to parallel with an axis of rotation of the rotor the closer the chord line is located relative to the rotor.

2. The unmanned aerial system (UAS) or claim 1 , wherein a direction of the wing twist is such that it maintains positive angle-of-attack with respect to an incoming flow relative to the body of the aircraft in forward flight.

3. The unmanned aerial system (UAS) of either of claims 1 or 2, wherein each wing has a cross-sectional profile in the form of an aerofoil.

4. The unmanned aerial system (UAS) of any one of the preceding claims, wherein the first forward wing and the first rear wing are located on the same side of the body and are connected by a first connection member, and the second forward wing and the second rear wing are located on the same side of the body and are connected by a second connection member.

5. The unmanned aerial system (UAS) of claim 4 wherein the connection member is generally planar and extends parallel to the axis of rotation.

6. The unmanned aerial system (UAS) of any one of the preceding claims, wherein each motor is located at or near a distal wing tip.

7. The unmanned aerial system (UAS) of claim 4 or 5, wherein adjacent to the rear wings, each of the first and second connection members has a region of increased thickness, in a direction extending parallel with the axis of rotation.

8. The unmanned aerial system (UAS) of claim 4 or 5, wherein the first and second forward wings, the first and second rear wings and the first and second connection members define a generally rectangular perimeter structure of the UAS.

9. The unmanned aerial system (UAS) of claim 1 wherein at the proximal regional of each wing, adjacent to the body, the chord line is close to parallel to a direction of flight in a forward flight mode, but slightly inclined by a local angle of attack of an aerofoil of the wing.

10. The unmanned aerial system (UAS) of any one of the preceding claims, wherein each wing includes at least one internal passage for housing at least one motor control and / or power cable.

11. The unmanned aerial system (UAS) of any one of the preceding claims, wherein each wing includes at least one gurney flap or other surface feature to modify aerodynamic performance, and located on an underside surface adjacent to a trailing edge.

12. An unmanned aerial system (UAS) comprising: a body; a first forward wing and a second forward wing extending away from opposing sides of the body; and a first rear wing and a second rear wing extending away from opposing sides of the body; each wing is associated with a motor having a rotor;wherein each wing is twisted about a longitudinally extending axis between a proximal region and a distal region, such that a trailing edge of each wing is more downwardly inclined in the vicinity of the distal region near a wing tip than at the proximal region adjacent to the body.

13. An unmanned aerial system (UAS) comprising: a body; a first forward wing and a second forward wing extending away from opposing sides of the body; and a first rear wing and a second rear wing extending away from opposing sides of the body; each wing is associated with a motor having a rotor; wherein each wing is twisted about a longitudinally extending axis between a proximal region and a distal region, such that a surface area of each wing, when viewed in a plane that is perpendicular to an axis of rotation of the respective rotor, is reduced beneath a swept area of said rotor.

14. A method of operating an unmanned aerial system (UAS), the UAS having a body; a first forward wing and a second forward wing extending away from opposing sides of the body; and a first rear wing and a second rear wing extending away from opposing sides of the body; a motor having a rotor is mounted to each wing; wherein each wing is twisted about a longitudinally extending axis between a proximal region and a distal region, such that a chord line taken through each wing becomes closer to parallel with an axis of rotation of the rotor the closer the chord line is to the rotor; the method including the step of operating the rear rotors at a faster rotational speed relative to the forward rotors to raise a rear end of the body so that each wing is aerodynamically generating lift in a region adjacent to the body.

15. The method of claim 12, wherein in forward flight the body is inclined so that a chord line of each wing at a proximal location adjacent to the body is offset relative to a direction of flight by a local angle of attack of the wing.

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