Patent Application
20230002043
Conventional unmanned aerial vehicles (UAVs) are provided with a plurality of motors, each with a rotor attached. Rotating the rotors with the motors produces lift for the UAV. The speed (and, in some UAVs, the angle) of the motors can be individually controlled, to maneuver the UAV, providing yaw, pitch and roll control.
UAVs which create lift by ‘flapping’ a set of wings, rather than rotating a set of rotors, have been developed. Such a UAV 1 is schematically illustrated in
The angle of attack α of the wing surface 4 is set to provide lift as the wing 2 is driven through the air (denoted by the arrows in Figures a) and b)) with an angle of attack α during each stroke of the wing 2. For each stroke, the spar 3 of the wing 2 acts as the leading edge. Although the magnitude of the angle of attack α may be substantially the same for each stroke, they are in opposing directions. Therefore, after the end of each stroke, the wing 2 needs to rotate so as to have the required angle of attack for the return stroke. The angle θ through which the wing 2 must rotate may be calculated as:
θ=180°−(α1+α2)
wherein α1 is the angle of attack in the first direction, and α2 is the angle of attack in the second (opposing) direction. For example, when α1 and α2 are both equal to 10°, the wing 3 must rotate through 160° when transitioning from one stroke to the next. It will be appreciated that when the angle of attack α is low, the wing 2 must rotate through a high angle θ when transitioning from one stroke to the next. The angle θ is the operational angular range of the wing 2. The wing may be mechanically limited only to rotate within the operational angular range θ. The angle of attack α may be different in each direction.
There may be no active control of the angle of the wing 2 during a stroke. The angle of the wing 2 is a consequence of the movement of air over the wing surface 4, as the wing 2 is driven through a stroke by the actuator. Consequently, when the wing needs to transition from one stroke to the next, the wing may not rotate towards the required angle of attack until there is sufficient air moving over the wing surface to cause the wing to rotate.
The rate of rotation of the wing 2 between strokes affects the amount of lift generated during the stroke. If the rate of rotation is slow, then a higher percentage of the total stroke time is taken up with rotating the wing 2 and a lower percentage of the total stroke time is taken up with the wing 2 being set at the required angle of attack α, generating lift.
The various phases that a flapping wing 2 goes through are indicated in
The present invention seeks to address at least one of the above problems.
Accordingly, the present invention provides a wing comprising a wing panel having a first longitudinal edge and a second longitudinal edge, the wing panel defining a wing surface between the first and second longitudinal edges, wherein the wing is configured such that, in use, either the first or second longitudinal edge may define a leading edge of the wing to generate lift.
In at least one embodiment, the wing panel is substantially symmetrical.
In at least one embodiment, the wing panel is symmetrical about a line of symmetry which is substantially equidistant from the first and second longitudinal edges.
In at least one embodiment, the wing panel is substantially planar.
In at least one embodiment, the wing panel is substantially non-planar.
In at least one embodiment, the wing panel comprises a first spar and a second spar and a membrane extending between the first and second spars, wherein the first and second spars define said first and second longitudinal edges respectively.
In at least one embodiment, the wing panel is flexible.
In at least one embodiment, the first longitudinal edge is non-parallel to the second longitudinal edge.
There is also provided a wing mounting, comprising:
In at least one embodiment, the wing is offset from the tilt axis.
In at least one embodiment, the centre of gravity of the wing bracket and wing assembly is offset from the tilt axis.
There is also provided a thrust generator comprising:
In at least one embodiment, the wing panel is configurable between:
In at least one embodiment, the thrust generator is configured to rotate the base about the stroke axis in a first direction when the wing panel is in the first configuration and to rotate the base about the stroke axis in a second direction when the wing panel is in the second configuration.
In at least one embodiment, in the first configuration the wing panel has a first angle of attack and in the second configuration the wing panel has a second angle of attack.
In at least one embodiment, the magnitude of the first angle of attack is substantially the same as the magnitude of the second angle of attack.
In at least one embodiment, the operational angular tilt range of the wing bracket is substantially equal to the sum of the first angle of attack and the second angle of attack.
In at least one embodiment, the motor is configured to oscillate the wing mounting about the stroke axis.
Embodiments of the present invention will now be described, by way of non-limiting example only, with reference to the Figures in which:
As schematically illustrated in
A spring mechanism may be adopted to urge the base 11 towards a particular (home) position about the stroke axis 13. The spring may be a helical spring.
The use of teeth 12, gear wheel 14 and oscillating motor 17 are not essential. Any other means to oscillate the base 11 about the stroke axis 13 may be adopted, including but not limited to direct drive rotary motor, indirect rotary drive motor, linear motor, pulleys, strings, gears, belt drive etc. In one embodiment, a mechanism may be connected between the motor and the base 11 to convert a continuous rotation of the motor into an oscillatory motion of the base 11.
The base 11 comprises two upstanding bosses 15 (one shown) and two protrusions 16 which act as mechanical stops.
The wing bracket 25 comprises a pin 26 which is rotatably received in the bosses 15 of the base 11 such that the wing bracket 25 is able to rotate about a tilt axis 27. The tilt axis 27 may be substantially perpendicular to the stroke axis 13. The tilt axis 27 may be substantially horizontal.
A wing 20 is secured to the top part of the wing bracket 25. In another embodiment, the wing 20 and bracket 25 may be integral with one another. The wing 20 comprises a wing panel 24 having a first longitudinal edge 5 and a second longitudinal edge 6, the wing panel 24 defining a wing surface between the first 5 and second 6 longitudinal edges, wherein the wing 20 is configured such that, in use, either the first 5 or second 6 longitudinal edge may define a leading edge of the wing 20 to generate lift.
The first longitudinal edge 5 and second longitudinal edge 6 are non-parallel to one another.
In the embodiment shown, the wing panel 24 is substantially symmetrical. The axis of symmetry is substantially parallel to the tilt axis 27. The line of symmetry is substantially equidistant from the first 5 and second 6 longitudinal edges. In another embodiment, the wing panel 24 may not be symmetrical.
In the embodiment shown in
The planar wing 20 is secured to the wing bracket 25 such that the plane of the wing panel 24 is substantially parallel to, but offset from, the tilt axis 27. That is to say that the tilt axis 27 does not pass through the plane of the wing 20.
The wing bracket 25 further comprises an anvil section 28, the underside of which provides one or more engaging surfaces 29.
The wing bracket 25 is constrained to rotate within an operational angular tilt range θ (see
When the wing bracket 25 rotates to a maximum extent in one direction (setting the wing 20 to a first angle of attack α1), further rotation of the wing 2 is prevented by the engaging surface 29 of the anvil 28 abutting the mechanical stop 16. See
When the wing 20 reaches the extent of the stroke, and decelerates, the air passing over the wing panel 24 reduces. At the same time, the inertia of the moving wing bracket 25 causes the wing bracket 25 to rotate about the wrist axis 27. The wing bracket 25 may continue to rotate about the wrist axis until the other engaging surface 29 of the anvil 28 abuts the other mechanical stop 16. See
During the transition between the first α1 and second α2 angles of attack, the wing panel 24 may momentarily be arranged substantially horizontally.
The anvil 28 and mechanical stop 16 arrangement effectively maintains the required angle of attack α during each stroke. The anvil and/or mechanical stops 16 may be configured to set the required angle of attack of the wing 20 in each direction.
It will be noted that, to transition from the first configuration where the wing panel 24 has a first angle of attack α1 and the second configuration where the wing panel 24 has a second angle of attack α2, the wing bracket 25 must rotate about the wrist axis 27 by an angle θ which is substantially equal to the sum of the first angle of attack α1 and the second angle of attack α2.
This contrasts to the arrangement schematically illustrated in
By comparison, with the wing mounting 10 embodying the present invention, the wing bracket 25 only needs to rotate through an angle substantially equal to the sum of the first angle of attack α1 and the second angle of attack α2. Conveniently, this allows the wing 20 to transition between the first and second configurations far more quickly than with the arrangement shown in
This conveniently reduces the time the wing 20 is in the reduced effect zone (
The wing 20 illustrated in
fi) and fii) schematically illustrate a wing 620 having a wing panel 624 having a first longitudinal edge 605 and a second longitudinal edge 606. The wing panel 624 is non-planar. The wing panel 624 is curved (as best seen in the end profile of
The wing panels 424 and 524 illustrated in
In the embodiments illustrated in
Alternatively, a wing panel of an embodiment of the invention may be flexible.
In an alternative embodiment, the wing panel may comprise a first spar and a second spar and a membrane extending between the first and second spars, wherein the first and second spars define the first and second longitudinal edges respectively. The first and second spars may be substantially rigid, and the membrane may be at least partially flexible. The first and second spars may alternatively be at least partially flexible. The flexibility of the first and second spars may differ to the flexibility of the membrane.
The membrane may extend between the first and second spars. Alternatively, the first and/or second spar may be arranged above or below the membrane. The wing surface may extend beyond the first and/or second spars.
When used in this specification and claims, the terms “comprises” and “comprising” and variations thereof mean that the specified features, steps or integers are included. The terms are not to be interpreted to exclude the presence of other features, steps or components.
The features disclosed in the foregoing description, or the following claims, or the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, as appropriate, may, separately, or in any combination of such features, be utilised for realising the invention in diverse forms thereof.
Although certain example embodiments of the invention have been described, the scope of the appended claims is not intended to be limited solely to these embodiments. The claims are to be construed literally, purposively, and/or to encompass equivalents.
| Number | Date | Country | Kind |
|---|---|---|---|
| 1917251.9 | Nov 2019 | GB | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/GB2020/053025 | 11/27/2020 | WO |
