WO2010140082A1

WO2010140082A1 - Unmanned aerial vehicle

Info

Publication number: WO2010140082A1
Application number: PCT/IB2010/052341
Authority: WO
Inventors: Oscar Philander; Mornay Riddles
Original assignee: Cape Peninsula University Of Technology
Priority date: 2009-06-04
Filing date: 2010-05-26
Publication date: 2010-12-09
Also published as: WO2010140082A9; ZA201003790B; ZA201003788B; ZA201003789B

Abstract

A UAV with an engine (34) attached to rear (38) of its fuselage by an engine mounting assembly with the rotational axis of the engine generally parallel with the axis (45) of the fuselage. The engine mounting assembly includes a fuselage bulkhead (40) and a parallel, spaced motor mount bulkhead (42) with the engine (34) attached to it. The mounting assembly also includes a number of connectors (64) that extend between the two bulkheads (40, 42) and resiliently compressible material (48) between the bulkheads in the vicinity of each connector. Each connector (64) can pivot relative to the bulkheads (40, 42) and presses on the bulkheads to compress the compressible material (48). The connectors (64) are adjustable to adjust the compressive load exerted on the compressible material (48). An undercarriage assembly (52) for a UAV comprising an upper cylinder (54) which is telescopically displaced relative to a lower cylinder (58) and a spring element (64) connected to both of the cylinders. A support structure (30) mounted in the front of the fuselage for supporting a camera and the support structure is configured to pivot the camera relative to the fuselage between different orientations.

Description

UNMANNED AERIAL VEHICLE

FIELD OF THE INVENTION

This invention relates to unmanned aerial vehicles (UAVs), especially for use in surveillance or the like.

BACKGROUND TO THE INVENTION

Various configurations of UAVs have been developed, ranging in size between model aircraft and full size aircraft and ranging in control between purely remote controlled UAVs and fully automated UAVs that follow pre-programmed flight paths with or without intelligence, geographic information, environmental feedback, etc.

The present invention relates primarily to low cost UAVs for use in surveillance, but some of the principles of the present invention can be applied much wider, in other UAVs and even in other aircraft.

In many instances, UAVs should preferably be small in size, e.g. to keep their cost of construction low and/or to limit their weight and wind resistance so that their fuel consumption can be kept low and/or their range kept long. However, the only appropriately sized engines that are commercially available to propel the UAVs are relatively simple in their configurations and are prone to vibration. In fact, most of these engines are single cylindered engines such as "glow-plug" engines. The sophisticated equipment in the UAVs, such as cameras and navigational equipment should be protected from engine vibrations to prevent damage to the equipment and to prevent affecting their operation adversely. In larger UAVs, using smoother running engines such as multi cylinder engines, the engine vibrations are small enough to allow the engines to be attached directly to the UAVs fuselage, but this does not work well in the case of courser running small engines, because the fuselage also houses the electronic equipment and accordingly, engine vibrations are transferred via the fuselage to the electronic equipment. In some configurations, an elastomehc sheet is attached to the fuselage, e.g. with spaced bolts and an engine mounting is also attached to the elastomeric sheet at locations spaced apart from the attachment to the fuselage, so that vibrations from the engine mounting are largely absorbed in the elastomer , rather than being transferred to the fuselage. These arrangements are effective in damping engine vibration at some frequencies, but at certain frequencies of engine operation, the elasticity of the sheet aggravates the vibration through resonance and the arrangement does not allow an adjustment of the elasticity and/or dampening to avoid excessive vibration.

Surveillance (and many other) UAVs need to have suspension in their undercarriage to prevent excessive movement of the fuselage and the components it caries (e.g. sophisticated cameras and navigational equipment) during take-off and/or landing. Further, UAVs often need to be steered while on the ground and accordingly, its undercarriage needs to be steerable. The complexity of existing UAV undercarriage arrangements that allow steering and suspension causes them to be expensive. These present configurations typically include a construction of two cylinders that can slide coaxially in a telescopic manner, with springs and/or dampers inside the cylinders to serve as suspension and with an external hinge mechanism welded to the outside of the cylinders to keep them aligned and thus allow steering.

One of the problems often experienced in low cost UAVs for surveillance is that they have cameras that are mounted on support structures that protrude below the fuselages of the UAVs, which exposes the camera to engine emissions in the case of a front-engined UAV, and exposes it to possible damage during take-off and landing, due to its proximity to the ground. The undercarriages of such UAVs are also typically large in order to keep the fuselages high off the ground, but the enlarged undercarriage causes drag during flight and increases costs. Part of the motivation for mounting cameras below the fuselages of UAVs is that the cameras need to be tilted relative to the UAV during surveillance and the support structures need to be large enough to allow this manoeuvrability and the camera lens needs to have unobstructed vision in various directions.

The operation of most commercially available surveillance cameras for these purposes allows the camera lens to be tilted relative to two right angled axes, but if surveillance is conducted on a moving subject from a UAV in flight and the subject travels erratically, e.g. a subject vehicle makes multiple random turns in a built-up area, while under surveillance, the bi-axial actuation of the camera lens is often unable to adjust quick enough to track the subject.

The present invention seeks to provide a UAV in which the shortfalls of existing UAVs mentioned above are ameliorated cost-effectively.

SUMMARY OF THE INVENTION

According to one aspect of the present invention, there is provided a UAV with an elongate fuselage having a front and a rear and an engine attached to the fuselage by way of an engine mounting assembly with a rotational axis of the engine extending generally parallel with the axis of the fuselage, said engine mounting assembly comprising: a fuselage bulkhead forming part of the fuselage; a motor mount bulkhead spaced from the fuselage bulkhead in a generally parallel arrangement, said engine being attached to the motor mount bulkhead; wherein said engine mounting assembly further includes a plurality of connectors extending between the fuselage bulkhead and motor mount bulkhead, each connector being configured to pivot relative to the bulkheads; and resiliently compressible material extending between the bulkheads in the vicinity of each connector; at least some of said connectors exerting a compressive load between said bulkheads to compress the resiliently compressible material and said connectors being adjustable to adjust the compressive load exerted on the resiliently compressible material.

The engine may be attached to the rear of the fuselage in a pusher configuration, with a propeller attached to the motor and facing in a rearwards direction.

Each connector may be an elongate screw-threaded fastener (e.g. a nut-and-bolt) extending between the bulkheads and the resiliently compressible material may be in the form of a plurality of short elastomehc tubes or other bodies, extending around the fasteners and being compressed between the bulkheads, at least in part.

According to another aspect of the present invention there is provided an undercarriage assembly for a UAV, said assembly including: an upper cylinder attached to a fuselage of the UAV and to a steering mechanism of the UAV, said upper cylinder being configured to rotate about its cylinder axis, in steering directions, under control of the UAVs steering mechanism; a lower cylinder that is generally coaxial with the upper cylinder with at least one wheel attached to a lower end of the lower cylinder, the upper and lower cylinders being in a telescopic configuration with an end of one cylinder inside the other cylinder, so that it can slide telescopically into the other cylinder so that the two cylinders together form a telescopic cylinder arrangement and the length of the arrangement, being the combined length of the two cylinders, can vary as the cylinders are telescopically displaced relative to each other; and a spring element connected to each of the cylinders and being configured to resist telescopic compression of the cylinder arrangement with resilient flexibility; wherein said spring element extends on the outside of the cylinders and has two ends that are pivotally attached to the respective cylinders in a manner that allows each end of the spring elements to pivot relative to its associated cylinder about an axis that extends transversely relative to the cylinder, said pivotal attachment of the spring element's ends and the resilience of the spring element serving to inhibit rotational movement between the cylinders, about their common axis.

The spring element may include a coil that extends helically around an axis that is generally parallel to the pivotal axes of the attachment of the ends of the spring element to each of the cylinders.

According to a further aspect of the present invention there is provided a UAV including: an elongate fuselage defining an internal cavity and having a front and a rear; a support structure mounted inside the cavity; and a camera supported by the support structure, with a lens that faces generally towards an underside of the front of the fuselage, in a normal orientation of the camera; wherein said support structure is mounted in the front of the fuselage and is configured to pivot the camera relative to the fuselage between different orientations in which the camera lens faces towards the underside of the fuselage at different angles relative to the orientation of the fuselage

The "underside" of the fuselage refers to its side that faces downwards when the fuselage is in an upright orientation. Accordingly, the underside of the fuselage will not necessarily face downwards during flight, depending on the orientation of the UAV during flight. Further, the direction "generally towards the underside of the fuselage" is not limited to a direction that extends exactly perpendicularly to the axis of the fuselage, but includes other directions oriented at acute angles relative to such a perpendicular direction. The term "camera" does not necessarily include all components (such as its power source, image processor, etc) that is required for the task of image capturing, but at least includes the camera's lens.

The support structure may be configured to pivot the camera about an axis that extends parallel (or aligned) with an axis of the fuselage. The support structure may be configured to pivot the camera about this axis to compensate for changes in orientation of the fuselage and the UAV may include a sensor to monitor its fuselage orientation. The support structure may be configured to direct the camera in a predetermined direction, e.g. towards a target location for surveillance.

The front of the fuselage may comprise a hollow nose cone and the camera may be mounted inside the nose cone, with an aperture defined in the nose cone that is generally aligned with the camera lens. The aperture may be covered with a transparent material. The nose cone may be rotatable relative to the rest of the fuselage and may rotate about the axis of the fuselage. The nose cone may be attachable to a part of the support structure.

The UAV may have its engine mounted in a pusher configuration, i.e. with the engine mounted forward of the propeller and with the propeller facing in a rearwards direction and the engine may be mounted in said pusher configuration on the rear of the fuselage.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the present invention, and to show how the same may be carried into effect, the invention will now be described by way of non-limiting example, with reference to the accompanying drawings in which:

Figure 1 is a three-dimensional view of a camera support structure for a UAV in accordance with the present invention; Figure 2 is a three-dimensional view of a bulkhead and stabilising servo of the structure of Figure 1 ;

Figure 3 is a sectional side view of the support structure of Figure 1 , inside the UAV; Figure 4 is a rear, starboard three-dimensional view of the rear of a UAV in accordance with the present invention; Figure 5 is a front, port three-dimensional sectional view of the rear end of the UAV of Figure 4; Figure 6 is a side view of the section of the rear end of the UAV shown in Figures 4 and 5; Figure 7 is a three-dimensional view of a forward undercarriage assembly of a UAV in accordance with the present invention; and Figure 8 is a sectional side view of the undercarriage assembly of Figure 7.

DETAILED DESCRIPTION OF THE DRAWINGS

Referring to the drawings, a UAV in accordance with the present invention has a hollow, generally cylindrical fuselage comprising of a resilient outer skin with an internal cavity and bulkheads extending into the cavity. A tail and wings are attached to the fuselage. The UAV is not shown in its entirety in the drawings, but these features are very common among fixed wing aircraft and UAVs.

Referring to Figures 1 to 3, the front of the UAVs fuselage includes a front or first bulkhead 10 that is disc shaped and extends transversely across an internal cavity of the fuselage. A second bulkhead 11 is spaced aft of the first bulkhead 10 in a parallel arrangement. A bracket 12 is attached to the second bulkhead 11 and supports a shaft 14 that extends forward, aligned with the axis of the fuselage and extends concentrically though an aperture 16 and a bracket 13 fastened to the first bulkhead 10.

A stabilised platform 18 is attached to the shaft 14, forward of the first bulkhead 10, but can rotate about the shaft relative to the first bulkhead. A stabilising servo 20 is attached to the first bulkhead and is attached to the stabilised platform via a servo arm 22 and linkage 24. Actuation of the servo 20 and its arm 22 and linkage 24, causes the platform 18 to rotate relative to the first bulkhead 10 and the rotation takes place about the shaft 14 and thus about the axis of the fuselage.

A camera (not shown) is fitted on a camera support bracket 26 that is fitted to the platform 18. The support bracket 26 extends forward from the platform 18 and is configured to support the camera with its lens facing generally downwards, when the fuselage is in an upright orientation and the platform 18 is in a normal or central position. The position of the camera lens, when in a tilted orientation (see explanation below), can be seen from the orientation of a lens support 28 of the camera bracket 26. The bracket 12, shaft 14, platform 18, servo 20 and camera bracket 26 together form a support structure for the camera that is generally indicated by reference numeral 30 and is housed in a hollow nose cone 32. The nose cone 32 is attached to the stabilising platform 18 and can rotate with the platform 18, camera bracket 26 and camera. An aperture or window (not visible in the drawings) is defined in the nose cone 32 and is aligned with the camera's lens and is preferably covered with a transparent cover or lens to protect the camera lens.

The flight of the UAV may be controlled remotely, via radio, may be programmed into a flight controller, or may use a variety and/or combination of remote controlled, automated or semi-automated aviation. However, in a preferred embodiment, the avionics of the UAV includes at least one sensor, such as a gyroscope, which monitors roll of the UAV and the avionics is configured to actuate the servo 20 automatically to compensate for any roll of the fuselage, by rotating the support structure 30 about the axis of the fuselage.

In use, the UAV flies along a flight path and while it does so, the camera records images of the ground below, through the window in the nose cone 32. The UAV is in an upright orientation most of the time, with the camera lens directed downwardly. However, if the UAVs fuselage deviates from its upright position by rolling, e.g. when it banks during a turn, the avionics causes the servo 20 to be activated and to rotate the support structure 30 about the fuselage axis to compensate for the fuselage roll. Accordingly, the camera is kept in an orientation with its lens directed downwardly, even though the UAV may not maintain its orientation.

If desired, the UAVs avionics can be used to control the support structure 30 to direct the camera at a surveillance target and this movement of the support structure 30, pivoting about the common axis of the shaft 14 and the fuselage of the UAV adds to the freedom with which the camera can be directed to follow a moving target. The support of the camera on this support structure thus adds an additional degree of freedom to the automated tracing movement of the camera. The sophistication and performance of tracking mechanisms differ between cameras, but the addition of automated rotation of the camera and support structure 30 as described above, can allow a lower cost camera to be used, with the same tracking capabilities as much more expensive cameras.

Referring to Figures 4 to 6, the UAV has an engine/motor 34 mounted in a pusher configuration at the rear of the fuselage 35, forward of a rearwards facing propeller 36. The rear end of the fuselage 35 is indicated by reference numeral 38 and includes a fuselage bulkhead in the form of a rear bulkhead 40 that is integrally formed with- or fixedly attached to the fuselage and a motor mount bulkhead 42 is attached to the rear bulkhead. The engine 34 is fixedly attached to the motor bulkhead 42 with a motor mount bracket 44. The rotational axis of the engine 34 is parallel with the axis of the fuselage 38 and in the illustrated embodiments, these axes are aligned and are indicated in Figures 5 and 6 by reference numeral 45.

The motor bulkhead 42 is spaced from the rear bulkhead 40 in a parallel arrangement and is attached to the rear bulkhead by way of six circumferentially spaced connectors. The connectors have been omitted from Figures 4 and 5, but a single connector 46 is shown in Figure 6. The connectors can be other fasteners, but in a preferred embodiment, each connector 46 is the form of a threaded stud 47 extending through the two bulkheads 40,42, with a spacer in the form of a rubber bush 48 extending around the shank of the stud and with rubber washers 50 around the stud on the outsides of the bulkheads. Metal washers 51 are provided on the outside of each rubber washer, with nuts 49 screwed onto the ends of the stud 47 on the outsides of the bulkheads. The nuts 49 are tightened, to compress the rubber washers 50 and bushes 48, but the flexibility of the rubber components allows the connector 46 to pivot relative to the bulkheads 40,42.

In use, vibrations from the motor 34 are transferred via the motor bracket 44 to the motor bulkhead 42, but the pivotal attachment of the connectors 46 to the bulkheads 40,42 allows the motor bulkhead 42 to vibrate, while the rear bulkhead 40 remains still or vibrates much less and the vibrations are absorbed to a large extent by the rubber bushes 48 and washers 50. As a result, the amount of engine vibrations that are transferred to the fuselage 38 and thus to the rest of the UAV, which houses avionics and the camera, is significantly reduced by the attachment of the motor bulkhead 42 to the rear bulkhead 40.

The stiffness of the rubber bushes and washers 48,50 and thus their dampening effect, as well as their elastic behaviour can be altered by tightening or loosening the compressive loads the nuts 49 exert on the rubber components. Changes in these characteristics of the rubber components also affect the frequencies at which the engine and/or the fuselage will resonate. Accordingly, in the event that unwanted vibration is still transferred from the engine 34 to the fuselage 35, e.g. a frequency that is particularly detrimental to the functioning of certain on-board electronic equipment, the nuts 49 can simply be twisted slightly, to alter the damping, elastic and resonant properties of the apparatus in a quick and cost effective manner.

Referring to Figures 7 and 8, a front undercarriage assembly for a UAV in accordance with the present invention is generally indicated by reference numeral 52. The assembly 52 includes an upper cylinder 54 that is housed partly inside the UAVs fuselage and that is pivotally attached to the fuselage by brackets 56 in an upright orientation, to pivot about its cylinder axis. This pivotal movement is controlled by a steering mechanism of the UAV and is transferred to the upper cylinder 54 via servo arms 66.

A lower cylinder 58 fits partly inside the lower end of the upper cylinder 54 in a telescopic configuration, so that it can slide up and down into and out of the upper cylinder and thereby changing the combined length of the telescopic cylinder arrangement. At the lower end of the lower cylinder 58, two wheels 60 are rotatable about a transverse shaft 62. The lower cylinder 58 is attached to the upper cylinder 54 by a spring element in the form of a coil spring 64 that is attached to each of these two cylinders in a way that prevents the cylinders 56,58 from rotating relative to each other, but permits telescopic movement, against the resistance of the spring. The spring 64 extends on the outside of the cylinders 54,58 and has two ends 68 that are pivotally attached to the respective cylinders by extending transversely through the cylinders so that each of the spring ends can pivot relative to its associated cylinder about an axis that extends transversely relative to the cylinder. The coil of the spring 64 is wound helically around a coil axis 70 that is generally parallel with the spring ends 68 and thus the pivot axes of the attachments of the spring ends to the cylinders 54,58. This aligned pivotal attachment of the spring ends 68 to the cylinders 54,58 allows the resilience of the spring element to inhibit rotational movement between the cylinders, about their common axis, but to allow the cylinders to move telescopically, against the flexible deformation of the spring.

In addition to the flexible, elastic suspension provided by the spring 64, the undercarriage 52 includes a damping arrangement inside the cylinders 54,58 in the form of an upper body 72 inside the upper cylinder 54 and a lower body 74 inside the lower cylinder 58, each carrying an elastomeric bush 76 that partly seals against the inner wall of the upper cylinder 54. When the cylinders 54,58 expand or are compressed telescopically, air either needs to escape from the cavity 78 between the bushes 76 or needs to enter the cavity. In each of these cases, the flow of air past the bushes 76 is inhibited by its partial seal and thus the telescopic movement is dampened.

The assembly 52 is relatively simple in construction and is much less costly than existing undercarriage assemblies with comparable features.

Claims

1. A UAV with an elongate fuselage (35) having a front and a rear (38) and an engine (34) attached to the fuselage by way of an engine mounting assembly with a rotational axis of the engine extending generally parallel with the axis (45) of the fuselage, said engine mounting assembly comprising: a fuselage bulkhead (40) forming part of the fuselage; a motor mount bulkhead (42) spaced from the fuselage bulkhead in a generally parallel arrangement, said engine being attached to the motor mount bulkhead; characterised in that said engine mounting assembly further includes a plurality of connectors (46) extending between the fuselage bulkhead and motor mount bulkhead, each connector being configured to pivot relative to the bulkheads; and resiliently compressible material (48) extending between the bulkheads in the vicinity of each connector; at least some of said connectors exerting a compressive load between said bulkheads to compress the resiliently compressible material and said connectors being adjustable to adjust the compressive load exerted on the resiliently compressible material.

2. A UAV as claimed in claim 1 , characterised in that said engine (34) is attached to the rear (38) of the fuselage (35) in a pusher configuration, with a propeller (36) attached to the motor and facing in a rearwards direction.

3. A UAV as claimed in claim 1 or claim 2, characterised in that each of said connectors (46) includes an elongate screw-threaded fastener (47) extending between the bulkheads (40,42).

4. A UAV as claimed in claim 3, characterised in that the resiliently compressible material is in the form of a plurality of bodies (48), extending around said fasteners and being compressed between the bulkheads (40,42), at least in part.

5. An undercarriage assembly (52) for a UAV, said assembly comprising: an upper cylinder (54) attached to a fuselage of the UAV and to a steering mechanism (66) of the UAV, said upper cylinder being configured to rotate about its cylinder axis, in steering directions, under control of the UAVs steering mechanism; a lower cylinder (58) that is generally coaxial with the upper cylinder with at least one wheel (60) attached to a lower end of the lower cylinder, the upper and lower cylinders being in a telescopic configuration with an end of one cylinder inside the other cylinder, so that it can slide telescopically into the other cylinder so that the two cylinders together form a telescopic cylinder arrangement and the length of the arrangement, being the combined length of the two cylinders, can vary as the cylinders are telescopically displaced relative to each other; and a spring element (64) connected to each of the cylinders and being configured to resist telescopic compression of the cylinder arrangement with resilient flexibility; characterised in that said spring element extends on the outside of the cylinders and has two ends (68) that are pivotally attached to the respective cylinders in a manner that allows each end of the spring elements to pivot relative to its associated cylinder about an axis that extends transversely relative to the cylinder, said pivotal attachment of the spring element's ends and the resilience of the spring element serving to inhibit rotational movement between the cylinders, about their common axis.

6. An undercarriage assembly as claimed in claim 5, characterised in that the spring element (64) includes a coil that extends helically around an axis (70) that is generally parallel to the pivotal axes of the attachment of the ends (68) of the spring element to each of the cylinders (54,58).

7. A UAV comprising: an elongate fuselage defining an internal cavity and having a front and a rear; a support structure mounted inside the cavity; and a camera supported by the support structure, with a lens that faces generally towards an underside of the front of the fuselage, in a normal orientation of the camera; characterised in that said support structure is mounted in the front of the fuselage and is configured to pivot the camera relative to the fuselage between different orientations in which the camera lens faces towards the underside of the fuselage at different angles relative to the orientation of the fuselage

8. A UAV as claimed in claim 7, characterised in that the support structure is configured to pivot the camera about an axis that is aligned with an axis of the fuselage.

9. A UAV as claimed in claim 8, characterised in that said support structure is configured to pivot the camera about said axis of the fuselage to compensate for changes in orientation of the fuselage.

10. A UAV as claimed in claim 9, characterised in that said UAV includes a sensor to monitor the orientation of its fuselage.

11. A UAV as claimed in claim 10, characterised in that said support structure is configured to direct the camera automatically in a predetermined direction.

12. A UAV as claimed in any one of claims 7 to 11 , characterised in that the front of the fuselage comprises a hollow nose cone and the camera is mounted inside the nose cone, with an aperture defined in the nose cone that is generally aligned with the camera lens.

13. A UAV as claimed in claim 12, characterised in that the aperture is covered with a transparent material.

14. A UAV as claimed in claim 12 or claim 13, characterised in that the nose cone is rotatable relative to the rest of the fuselage about the axis of the fuselage.

15. A UAV as claimed in any one of claims 12 to 14, characterised in that the nose cone is attachable to a part of the support structure.

16. A UAV as claimed in any one of claims 7 to 15, characterised in that an engine of the UAV is mounted in a pusher configuration on the rear of the fuselage.