GB2529896A

GB2529896A - Multirotor

Info

Publication number: GB2529896A
Application number: GB1415825.7A
Authority: GB
Inventors: Richard Nathan Hadder
Original assignee: Individual
Current assignee: Individual
Priority date: 2014-09-05
Filing date: 2014-09-05
Publication date: 2016-03-09
Anticipated expiration: 2034-09-05
Also published as: GB201415825D0; GB2529896B

Abstract

A multi-rotor system 2 comprises a plurality of rotors 4 on more than one plane. The rotors are positioned within frames 14 that include circumferential ducting 10. Where rotors overlap in plan view there are arranged partitions to ensure that airflow through a rotor in an upstream plane does not pass through a rotor in a downstream plane. The multi-rotor system is primarily intended for use in providing lift for a UAV. It also has applications as a cooling fan such as for engine radiators. The rotor arrangement is such as to maximise air flow and minimise plan form area.

Description

MULTI ROTOR

Field of the Invention

This invention relates to multirotors, such as may be used in applications such as cooling fans for cars or S in multirotor-type UAVs.

Background

Rotors comprising rotary arms arranged about a central hub are a common mechanism utilised in many different applications. Many fans, especially electrically-powered ones, are based on rotors. The extent of air flow through a rotor can be sufficient to generate aerodynamic lift and thrust, and this is the basis of the helicopter.

In recent years there has been growing interest in multirotors -arrangements of multiple rotors on a frame or structure. Advantageously, multirotors do not require the use of the complex variable pitch rotors required to control the motion of conventional single-rotor or double-rotor helicopters; control of multirotor vehicle motion is as simple as varying the relative speed of each rotor to change the thrust and torque produced by each.

Although manned multirotor vehicles have been designed, much interest has revolved around the use of rotors in unmanned aerial vehicles or UAVs. Ranging from simple radio controlled toys to sophisticated tools for use in espionage and military applications, UAVs or "drones" have become increasingly well-known, and interest is growing in commercial applications thereof.

A disadvantage of existing multirotor systems is their plan form area. With each rotor arranged coplanar to each other, adding an additional rotor to such conventional systems inevitably requires increasing the minimum plan form area of the system, unless the size of rotors is decreased (with a corresponding loss of air flow). It would be advantageous to be able to produce multirotor systems with smaller plan form areas for a number of applications; in particular, smaller UAVs could be useful for indoor applications, or when used for espionage or military purposes will be more difficult to spot and shoot down.

Summary of the Invention

Firstly, the invention provides a rnultirotor system comprising at least one rotor on a first plane, at least one rotor on a second plane displaced from the first plane. and partitions arranged between neighbouring rotors on the first and second plane, such that each partition impedes air flow from a said rotor in the first plane from flowing through a said rotor in the second plane. Preferably, there are an equal number of rotors on the first and second planes. Preferably, there are at least four rotors in total.

In particular, 6 rotors can be provided (with 3 rotors in a triangular arrangement on each plane) to provide a multirotor suitable for a hexacopter with a plan form area substantially smaller than the plan form area of a conventional hexacopter (in which al1 the rotors are essentially coplanar). Likewise, 8 rotors can be provided (with 4 rotors in a square arrangement on each plane) to provide a multirotor suitable for an octocopter. In principle, there is no upper limit to the number of rotors that can be used in multirotors according to the present invention, though in practice size, weight and budgetary requirements may impose a practical limit for many applications.

The partitions are required to shield each rotor from interference caused by the air flow from its neighbouring rotors on the other plane. Preferably, at least one partition (preferably all partitions) is shaped such that each of the rotors neighbouring tie partition is fating a concave surface of the partition as the partition crosses the plane of the rotors. Preferably, at least one of the partitions (more preferably all partitions) comprises a complex curved surface whose cross-section (in a plane perpendicular to the direction of radial extension of the partition) describes a curve describes a curve which transitions from a concave to a convex with a minimum slope of 45° (measured relative to a plane parallel to the first or second planes). More preferably, the curve may be described by the equation: y=x(ax2+b) or y=-x(ax2+b) wherein the y-axis is an axis perpendicular to the first and second planes, the x-axis is an axis parallel to the first and second planes and perpendicular to the direction of radial extension of the partition, the origin of the x andy axes are at the centre of the curve, a and b are constants selected to provide the curvature and the angle at the centre of the curve desired, a >0 and b »= 1, wherein the angle at the centre of the curve is defined by the gradient of the arc when x = 0. By definition, when x = 0 b will equal at least 1, which means that the gradient at the centre of the curve will be at least 1, which will correspond to an angle at the centre of the curve of at least 45°; the higher the gradient, the greater the angle.

Preferably, the cross-section of the partition changes over its radial extent, such that at the inner and outer extremities of the partition a cross-section of the partition in a plane perpendicular to the direction of radial extension of the partition extends in a direction perpendicular to the planes, and the complex curved surface is located at a midpoint between the inner and outer extremities.

It is preferable that the multirotor comprise circumferential ducting surrounding each rotor. This will make it more difficult for the tips of the rotors to accidentally hit nearby objects, protecting both the tips and objects (or people) who may be endangered by them. Where such ducting is present, it is preferable that the interplanar partitions connect the circumferential ducting surrounding each rotor on the first plane to the circumferential ducting surrounding neighbouring rotors on the second plane. This allows the ducting and partitions to be produced as a unitary, integral body, decreasing manufacturing costs.

It is preferable to arrange the rotors such that the overlap of any one rotor on the first or second plane with its two neighbours on the other plane is between 0% and 50%. More preferably, the overlap is between 30% and 35%.

For some applications it is preferable that the relative speed of each rotor can be controlled.

In a second aspect, the invention provides a frame for a multirotor, wherein the frame comprises circumferential ducting and partitions formed as a unitary, integral body as described above.

In a third aspect, the invention provides an aerial vehicle comprising a multirotor system as described above. This vehicle may be manned or may be a UAV and may be operated remotely. One example of such a vehicle could be a hexacopter or octocopter.

In a fourth aspect, the invention provides a fan system comprising a multirotor system as described above.

In a fifth aspect, the invention provides a cooling system comprising a multirotor system as described above.

In a sixth aspect, the invention provides a radiator comprising a multirotor system as described above.

The multirotor system could, due to being able to fit more rotors into a smaller plan form area than prior art systems, be of use in applications in which radiator fans must fit within particular size limits; one example would be for a radiator adapted for use in a car.

In a seventh aspect, the invention provides a car comprising a radiator which comprises a multirotor system as described above.

Description of Drawings

Fig. 1 is an isometric view of a hexacopter incorporating a multirotor according to the present invention, S with various preferable features included.

Fig. 2 is a schematic top-down view of rotor arrangement in a prior art multirotor.

Fig. 3 is a schematic top-down view of rotor arrangement in a multirotor according to the present invention.

Fig. 4a-b provides a series of views of a frame for a nultirotor system according to the present invention Fig. 5a-d provides a series of cross-sections of partitions used in multirotors according to the present invention.

Detailed Description

Fig. 1 presents an isometric view of a hexacopter 2 comprising a multirotor according to the present invention, depicting a number of preferred features. The multirotor comprises six rotors 4, 6, three rotors 4 on a first plane and three rotors 6 on a second plane, arranged about a central hub 12. Each rotor 4 on the first plane neighbours two rotors 6 on the second plane and vice versa; between each such neighbouring rotor 4,6 is a partition 8. Surrounding each rotor is a circumferential ducting 10; each partition 8 connects a ducting lOon one plane to a ducting lOon the other plane.

Although the depicted multirotor in the figures is designed for a hexacopter 2, multirotors according to the present invention can have more or less rotors 4, 6, down to a minimum of one per plane. It is even possible to produce multirotors according to the present invention wherein the number of rotors 4, 6 on each plane is not equal -for instance, with four rotars 4 on the upper plane and two rotors 6 underneath. Multirotors according to the present invention may even have an odd number of rotors in total. Preferably, however, multirotors according to the present invention have an equal number of rotors on each plane.

The purpose of the partitions S is to reduce or even eliminate turbulence arising from the air flow from neighbouring rotors 4, 6 interacting. If the partitions 8 were not in place, the rotors 6 on the lower plane would be operating within the air flow from the rotors 4 on the upper plane, which would cause a severe loss of efficiency. Preferably, the partitions Swill possess a complex, curved shape with convex and concave sections as depicted in this figure and as discussed further below in order to minimise (and ideally eliminate) the air flow from the upper plane rotors (4) experienced by the lower plane rotors 6.

S

The circumferential ducting 10 about the rotors 4,6 prevents damage to the rotor tips and objects and injury to human beings or animals in the event of a collision. It also has the beneficial effect of reducing tip vortex losses.

A major advantage of the present invention is illustrated by Figures 2 and 3, which provide extremely abstract and simplified depictions of rotor arrangement in a prior art rriultirotor (Fig. 2) and a multirotor according to the present invention (Fig. 3). In the prior art arrangement in Fig. 2 the rotors 4 are all arranged on the same plane. Conventional hexacopter multirotors have the rotors 4 arranged in a hexagonal pattern, so that each rotor 4 is equidistant from the centre and a high degree of rotational symmetry is achieved. If we assume that a circular soace of 100mm diameter is allocated to each rotor 4, then the distance between the centre of one rotor (4) and the centre of the opposite rotor 4 is 200mm, the maximum width of the rotor arrangement (as measured from the edge of one rotor 4 to the edge of the opposite rotor 4) comes to 300mm, and the plan form area occypied by the arrangement comes to 0.057m2.

In Figure3 we see how multirotors according to the present invention save space. The rotors 4, 6 are arranged so that there are 3 on each plane, arranged in a triangular conformation, with the two triangles angularly displaced from one another. A multirotor according to the present invention can be designed to minimise multirotor width and area, such that when 100mm diameter circular spaces are allocated to each rotor 4, 6 the distance between the centre of one rotor and the centre of the opposite rotor is 115.45mm, the maximum width of the multirotor system is 215.47mm, and the plan form area occupied by the arrangement comes to 0.033m2.

It will be noted from Fig. 3 that when viewed from its free side each rotor 4,6 is overlapped by its neighbours on the opposite plane. In the depicted arrangement where use of space is minimised, the overlap consists of 37.5% of the area of each rotor 4, 6. In theory a multirotor according to the present invention could function with an extremely high extent of overlap, but in practice it is found that efficiency lass take5 place above 50% overlap. Preferably, therefore, the overlap is between 0 and 50%.

Even more preferably, the overlap is between 30 and 35%.

S

Fig. 4a depicts an isometric view of another aspect of the present invention, a frame 14 for a multirotor as described above. The frame 14 consists of the circumferential ducting 10 and partitions 8 described above formed as a single body, for instance as produced from a mould or a body produced by a 3D printing process. Preferably, such a frame 14 would also include the central hub 12, which confers S greater rigidity on the frame. Figure 4b depicts a top-down view of such a frame 14. It will be noted that the partitions Bare arranged to coincide with the regions of overlap between neighbouring rotors 4, 6.

The partitions 8 in the frame are a complex shape just like the partitions Sin the multirotor depicted in Figs. land 3. To further discuss this shape, it is useful to provide illustrative cross-sections taken at different points along the partition 8.

Such cross-sections are shown in Figs. Sa-d. In each case the cross-section is taken in a plane perpendicular to the direction of radial extension of the partition 8. Figure Sa shows a cross-section taken at the line A-A', which is at the outermost radial extremity of the partitionS. It will be seen that the cross-section is a straight, vertical wall, since this is a point where the ducting lOin the upper plane is directly vertically above the ducting lOin the lower plane. As we progress radially from the outermost extremity of the partitionS to the point of maximum curvature, we see the curvature of the partition 8 become more and more pronounced in the cross-sections taken at the lines B-B' (Fig. Sb) and C-C' (Fig. Sc). At the line D-D' the point of maximum curvature is reached. (Preferably, in a multirotor this would coincide this coincides with the point where maximum overlap between the upper and lower rotors 4, 6 was attained). From line D-D' to the innermost radial extremity of the partition 8, the curvature of the cross-section decreases until a vertical wall is attained at the innermost radial extremity.

At the point of maximum curvature the minimum angle described by the cross-section (measured between a tangent to the cross-section and the lower plane) is at least 45°. If the angle is less than this efficiency is lost due to flow reversal. The curve described by the cross-section here can be described by the equation: y = -x(ax2 + b) wherein the y-axis is an axis perpendicular to the first and second planes, the x-axis is an axis parallel to the first and second planes and perpendicular to the direction of radial extension of the partition, the origin of the x andy axes are at the centre of the curve, a and b are constants selected to provide the curvature desired, a >0 and b »= 1, wherein the angle at the centre of the curve is defined by the gradient of the curve when x = 0. So, for instance, when b = 1 the gradient of the curve is 1, which corresponds to an angle of 45°.

Partitions 8 can also be used where the curve described by the cross-section at the point of maximum curvature has a curve described by the equation: y = x(ax2 + b) It is preferable that the partitions 8 are arranged such that each rotor 4, 6 is facing a concave surface as the curve of the partitions 8 crosses the plane of the rotors. So, for instance, in the embodiment depicted in Fig. Sd, the upper rotor 4 would be on the D' side of the partition Sand the lower rotor 6 would be on the D side of the partition 8.

As well as cubical parabolas as described above, other curves with other equations could be used in conjunction with the present invention, but it is preferable that they be arcuate curves which are oppositely curved on either side of the mid-point, when viewed in sections taken perpendicular to the radial direction, so that again each rotor 4, 6 is facing a concave surface as the curve of the partitions 8 crosses the plane of the rotors.

Multirotors according to the present invention reduce or eliminate rotor interaction and interference between overlapping rotors (4, 6), allowing the pla form area of the multirotor to be reduced with only a minimal reduction (if any) in efficiency. Especially when preferable features as described are implemented, multirotors according to the present invention are able to maximise air flow whilst minimising plan form area. This has a number of useful applications. In the field of rotary wing vehicles, manned or unmanned vehicles can be produced with a reduced plan form area. Smaller UAVs may be of particular use in espionage applications and it is anticipated that the primary use of the multirotor would be for a UAV, particularly since this is the primary use of the prior art multirotors that the present invention improves on. In addition, because of the small area, the multirotor may be of use in fan systems, cooling systems and radiators in applications in which space is at a premium -for instance, in car radiator design.

Claims

Claims 1: A multirotor system comprising: at least one rotor on a first plane; at least one rotor on a second plane displaced from the first plane; and partitions arranged between neighbouring rotors on the first and second plane, such that each partition impedes air flow from a said rotor in the first plane from flowing through a said rotor in the second plane.

2: A multirotor system according to claim 1, in which there are an equal number of rotors on the first and second planes.

3: A multirotor system according to any preceding claim, in which there are at least 4 rotors in total.

4: A multirotor system according to any preceding claim, in which there are SorB rotors in total.

5: A multirotor system according to any preceding cairn, in which there are 6 rotors in total with 3 rotors in a triangular arrangement on each plane.

6: A multirotor system according to any of claims 1-4, in which there are 8 rotors in total with 4 rotors in a square arrangement on each plane.

7: A multirotor system according to any preceding c1aim, wherein at least one partition is shaped such that each of the rotors neighbouring the partition is facing a concave surface of the partition as the partition crosses the plane of the rotors.

8: A multirotor system according to any preceding claim, in which at least one partition comprises a complex curved surface whose cross-section (in a plane perpendicular to the direction of radial extension of the partition) describes a curve which transitions from a concave to a convex with a minimum slope of 450 (measured relative to a plane parallel to the first or second planes).

9: A multirotor system according to claims, in which the curve may be described by the equation: y=x(ax2+b) or y=-x(ax2+b) wherein the y-axis is an axis perpendicular to the first and second planes, the x-axis is an axis parallel to the first and second planes and perpendicular to the direction of radial extension of the partition, the origin of the x andy axes are at the centre of the curve, a and bare constants selected to provide the curvature desired, a >0 and b »= 1, wherein the angle at the centre of the curve is defined by the S gradient of curve when x = 0.

10: A multirotor system according to claim 8 or 9, in which at the inner and outer extremities of the partition a cross-section of the partition in a plane perpendicular to the direction of radial extension of the partition extends vertically in a direction perperdicular to the planes, and the complex curved surface is located at a midpoint between the inner and outer extremities.

11: A rnultirotor system according to any preceding claim, wherein the rotors are arranged such that the overlap of any one rotor on the first or second plane with its two neighbours on the other plane is between 0% and 50%.

12: A multirotor system according to any preceding claim, wherein the rotors are arranged such that the overlap of any one rotor on the first or second plane with its two neighbours on the other plane is between 30% and 35%.

13: A multirotor system according to any preceding claim, wherein the relative speed of each rotor can be controlled.

14: A multirotor system according to any preceding claim, further comprising circumferential ducting surrounding each rotor.

15: A multirotor system according to claim 14, in which the partitions connect the circumferential ducting surrounding each rotor on the first plane to the circumferential ducting surrounding neighbouring rotors on the second plane.

16: A frame for a multirotor system according to claim 15, comprising circumferential ducting and partitions formed as a unitary, integral body.

17: A frame according to claim 16, additionally comprising a central hub.

18: A multirator system comprising a frame according to claim 16 or 17.

19: An aerial vehicle comprising a multirotor system according to any of claims ito 15 or 18.

20: An aerial vehicle according to claim 19 wherein the vehicle is an unmanned aerial vehicle (UAV).

21: An aerial vehicle according to claim 19 wherein the vehicle is manned.

22: An aerial vehicle according to any of claims 19-21 wherein the vehicle is operated remotely.

23: An aerial vehicle according to any of claims 19-22 wherein the vehicle is a hexacopter or octocopter.

24: A fan system comprising a multirotor system ac:ording to any of claims 1-15 or 18.

25: A cooling system comprising a multirotor system according to any of claims 1-15 or 18.

26: A radiator comprising a multirotor system according to any of claims 1-15 or 18.

27: A radiator according to claim 26, adapted for use in an internal combustion engine or motor vehicle.

28: An internal combustion engine or motor vehicle comprising a radiator according to claim 26 or 27.Amendments to the claims have been made as follows Claims 1: A multirotor system comprising: at least one rotor on a first plane; at least one rotor on a second plane displaced from and substantially parallel to the first plane; wherein the rotors are arranged such that the overlap of any one rotor on the first or second plane with its neighbouring rotors on the other plane is between 0% and 50%; and partitions arranged to coincide with the regions of overlap between neighbouring rotors on the first and second plane, such that each partition impedes air flow from a said rotor in the first plane from flowing through a said rotor in the second plane.2: A multirotor system according to claim 1, in which there are an equal number of rotors on the first and second planes.3: A multirotor system according to any preceding claim, in which there are at least 4 rotors in total.4: A multirotor system according to any preceding claim, in which there are 6 orB rotors in total.5: A multirotor system according to any preceding claim, in which there are 6 rotors in total with 3 0 rotors in a triangular arrangement on each plane.6: A multirotor system according to any of claims 1-4, in which there are 8 rotors in total with 4 rotors in a square arrangement on each plane.7: A multirotor system according to any preceding claim, wherein at least one partition is shaped such that each of the rotors neighbouring the partition is facing a concave surface of the partition as the partition crosses the plane of the rotors.8: A multirotor system according to any preceding claim, in which at least one partition comprises a complex curved surface whose cross-section (in a plane perpendicular to the direction of radial extension of the partition) describes a curve which transitions from a concave to a convex with a minimum slope of 45° (measured relative to a plane parallel to the first or second planes).9: A multirotor system according to claim 8, in which the curve may be described by the equation: y=x(ax2+b) or y=-x(ax2+b) wherein the y-axis is an axis perpendicular to the first and second planes, the x-axis is an axis parallel to the first and second planes and perpendicular to the direction of radial extension of the partition, the origin of the x and y axes are at the centre of the curve, a and bare constants selected to provide the curvature desired, a >0 and b »= 1, wherein the angle at the centre of the curve is defined by the gradient of curve when x = 0.10: A multirotor system according to claim 8 or 9, in which at the inner and outer extremities of the partition a cross-section of the partition in a plane perpendicular to the direction of radial extension of the partition extends vertically in a direction perpendicular to the planes, and the complex curved surface is located at a midpoint between the inner and outer extremities.11: A multirotor system according to any preceding claim, wherein the rotors are arranged such that the overlap of any one rotor on the first or second plane with its neighbouring rotors on the other plane is between 30% and 35%. (012: A multirotor system according to any preceding claim, wherein the relative speed of each rotor can be controlled.13: A multirotor system according to any preceding claim, further comprising circumferential ducting surrounding each rotor.14: A multirotor system according to claim 13, in which the partitions connect the circumferential ducting surrounding each rotor on the first plane to the circumferential ducting surrounding neighbouring rotors on the second plane.15: A frame for a multirotor system according to claim 14, comprising circumferential ducting and partitions formed as a unitary, integral body.16: A frame according to claim 15, additionally comprising a central hub.17: A multirotor system comprising a frame according to claim 15 or 16.18: An aerial vehicle comprising a multirotor system according to any of claims ito 14 or 17.19: An aerial vehicle according to claim 18 wherein the vehicle is an unmanned aerial vehicle (UAV).20: An aerial vehicle according to claim 18 wherein the vehicle is manned.21: An aerial vehicle according to any of claims 18-20 wherein the vehicle is operated remotely.22: An aerial vehicle according to any of claims 18-21 wherein the vehicle is a hexacopter or octocopter.23: A fan system comprising a multirotor system according to any of claims 1-14 or 17.24: A cooling system comprising a multirotor system according to any of claims 1-14 or 17.25: A radiator comprising a multirotor system according to any of claims 1-14 or 17.26: A radiator according to claim 25, adapted for use in an internal combustion engine or motor vehicle. (027: An internal combustion engine or motor vehicle comprising a radiator according to claim 25 or 26. r aD r