WO2007126405A2

WO2007126405A2 - Airfoil for micro air vehicle

Info

Publication number: WO2007126405A2
Application number: PCT/US2006/011969
Authority: WO
Inventors: Peter Geza Ifju; Bret Kennedy Stanford; Roberto Albertani
Original assignee: University Of Florida Research Foundation Inc.
Priority date: 2006-03-30
Filing date: 2006-03-30
Publication date: 2007-11-08
Also published as: WO2007126405A3

Abstract

An airfoil for a micro air vehicle that includes components enabling the airfoil to adjust the angle of attack (AOA) of the airfoil in response to wind gusts, thereby enabling the airfoil to provide smooth flight. The airfoil may include a first compliant region positioned between an inboard section and a first outboard section and may include a second compliant region between a second outboard section and the inboard section. The compliant regions enable the first and second outboard sections to bend about a leading edge section and move relative to an inboard section. This action creates smoother flight due to numerous aerodynamic advantages such as a change in the angle of attack and improved wind gust rejection due to adaptive washout as a result of the airfoil flexing, twisting and decambering.

Description

AIRFOIL FOR MICRO AIR VEHICLE

FIELD OF THE INVENTION

This invention is directed generally to micro air vehicles, and more particularly, to airfoil configurations for micro air vehicles.

BACKGROUND

Micro air vehicles generally are relatively small unmanned flying objects, such as

those having wingspans less than about ten inches. Micro air vehicles are often powered by

small gasoline or electric propeller driven engines. Micro air vehicles are relatively

lightweight vehicles capable of being used for a variety of purposes, such as for recreation, reconnaissance, and other purposes. Because of their small size, micro air vehicles lend

themselves to a variety of uses. For instance, micro air vehicles have been used to carry

cameras and other payload on a battlefield and in other surveillance operations.

Many micro air vehicles are formed from rigid airfoils that create erratic flight in gusty wind conditions. Small rigid airfoils sized to be used with micro air vehicles typically

lack the capability to produce smooth flight in gusty conditions. However, smooth flight is

desired during surveillance operations to enable a camera contained within the micro air

vehicle to take high quality pictures. Thus, a need exists for an airfoil for micro air vehicles that is capable of providing smooth flight in gusty wind conditions. SUMMARY OF THE INVENTION

This invention is directed to an airfoil for a micro air vehicle that includes components enabling the airfoil to adjust the angle of attack (AOA) of the airfoil in response

to wind gusts, thereby enabling the airfoil to provide smooth flight. In addition, the airfoil

may enable a micro air vehicle to fly at increased angles of attack relative to conventional

airfoils before stall is encountered, and as such, can aid in transition to a hover mode. The airfoil may include a leading edge section, an inboard section positioned between a first and

second outboard sections and aft of the leading edge section. The leading edge section may

be formed from a first material, wherein the leading edge section may be configured to bend

in a first direction such that ends of the leading edge may be bent towards a pressure side of

the airfoil but may not bend substantially in a second, generally opposite direction toward the suction side of the airfoil. The airfoil may include a first compliant region positioned

between the inboard section and the first outboard section and may include a second

compliant region between the second outboard section and the inboard section. The first and

second compliant regions may enable the first and second outboard sections to move relative

to the inboard section by bending about a leading edge section forming a leading edge of the airfoil. This movement of the first and second outboard sections creates smoother flight due

to a change in the angle of attack reduced drag due to the curvature of a leading edge section

and improved wind gust rejection due to adaptive washout as a result of the airfoil flexing, twisting and decambering.

The first and second compliant regions may be formed from one or more compliant

regions positioned between the first outboard section and the inboard section and the second

outboard section and the inboard section, respectively. The first and second compliant regions may extend from proximate the leading edge section to the trailing edge enabling the

first and second outboard sections to move relative to the inboard section about the leading edge section. The first or second compliant region, or both, may be formed from one or

more slots extending from proximate the leading edge section to the trailing edge. One or more seals may be positioned between first and second outboard sections and the inboard

section. The seals may include an end plate extending from a suction side of the airfoil. In

another embodiment, the first compliant region, may be formed from material attached to the

first outboard section and attached to the inboard section, wherein a length of the material is

greater than a distance between the first outboard section and the inboard section, thereby

permitting the first outboard section to move relative to the inboard section by bending about

the leading edge section. The second compliant region, may likewise be formed from a material attached to the second outboard section and attached to the inboard section, wherein

a length of the material is greater than a distance between the second outboard section and

the inboard section, thereby permitting the second outboard section to move relative to the

inboard section by bending about the leading edge section.

The first and second outboard sections may also include first and second camber

adjustable regions formed from a flexible material that changes camber upon interaction with

a wind gust. The first and second camber adjustable regions may be formed from a flexible

material, such as, but not limited to, latex. The first and second camber adjustable regions

may extend from the leading edge section toward the trailing edge, and may form the trailing edge in some embodiments. The first and second camber adjustable regions may be formed

from a resilient, flexible material having a camber forming a concave surface facing

downward that improves wind gust rejection due to adaptive washout as a result of the material flexibly decambering. The first or section outboard section, or both, may include

one or more battens extending from the leading edge section toward the trailing edge and may be attached to the at least one layer of a resilient, flexible material.

The airfoil may also include a first outboard perimeter support structure extending

along a perimeter of the first outboard section and attached to the leading edge section. The

airfoil may also include a second outboard perimeter support structure extending along a perimeter of the second outboard section and attached to the leading edge section. The first

and second outboard perimeter support structures may provide structural support to the first

and second camber adjustable regions. In at least one embodiment, the leading edge section,

the inboard section, the first outboard perimeter support structure, and the second outboard

perimeter support structure comprise a monolithic structure, which may be formed from a carbon fiber epoxy.

An advantage of this invention is that the angle of attack of the airfoil may be

changed in response to wind gusts, thereby enabling the airfoil to provide smoother flight than other airfoils.

Another advantage of this invention is that the airfoil with the first and second outboard sections separated from an inboard section creates greater lifting force than

comparable airfoils without the first and second outboard sections.

Yet another advantage of this invention is that the airfoil may enable a micro air

vehicle to fly at increased angles of attack relative to conventional airfoils before stall is encountered, and as such, can aid in transition to a hover mode. Another advantage of this invention is that a micro air vehicle incorporating the

airfoil of this invention may fly at slower speeds while maintaining the ability to reject wind

gusts through the motion of the first and second outboard sections.

Still another advantage of this invention is that the bendable airfoil may be produced relatively inexpensively.

Another advantage of this invention is that the airfoil is durable and capable of

withstanding crash landings.

These and other advantages will become obvious upon review of the detailed written

description below of these and other embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and form a part of the

specification, illustrate preferred embodiments of the presently disclosed invention and,

together with the description, disclose the principles of the invention.

Figure 1 is a perspective view of a micro air vehicle of this invention with a second

outboard section bent toward a pressure side of the airfoil about a leading edge section.

Figure 2 is a top view of an airfoil of this invention.

Figure 3 is a top view of an alternative airfoil of this invention.

Figure 4 is a top view of yet another alternative airfoil of this invention.

Figure 5 is a perspective view of still another alternative airfoil of this invention.

Figure 6 is a detailed view of a trailing edge of the airfoil taken at line 6-6 in Figure 2.

Figure 7 is a detailed view of a trailing edge of the airfoil taken at line 7-7 in Figure 3. Figure 8 is a graph of the coefficient of lift vs. the angle of attack for three airfoil designs compared against an airfoil design having compliant regions of this invention. All four airfoils had the same overall geometric shape. The rigid airfoil was rigid in its entirety.

The PR 07 airfoil had a camber adjustable region aft of a leading edge region and was

supported by a perimeter reinforcement. The BR 09 airfoil had a camber adjustable region

aft of a leading edge region and was supported by batten reinforcements. The PR 10 airfoil had compliant regions of the invention.

DETAILED DESCRIPTION OF THE INVENTION

As shown in Figures 1-8, this invention is directed to an airfoil 12 for a micro air

vehicle 10 that includes components enabling the airfoil 12 to adjust the angle of attack (AOA) of the airfoil in response to a wind gust, thereby enabling the airfoil 12 to provide smooth flight. In addition, the airfoil 12 may enable a micro air vehicle to fly at increased

angles of attack relative to conventional airfoils before stall is encountered, as shown in

Figure 8, and as such, can aid in transition to a hover mode. In particular, stall occurs when the coefficient of lift decreases as the angle of attack increases. Thus, it can be seen in

Figure 8, that the PR 10 airfoil, as shown in Figure 2, was able to achieve higher angles of

attack before encountering stall.

The airfoil 12 may include a first compliant region 14 positioned between an inboard

section 16 and a first outboard section 18 and may include a second compliant region 20 positioned between a second outboard section 22 and the inboard section 16. The compliant

regions 14, 20 enable the first and second outboard sections 18, 22 to bend about a leading edge section 24. This action enables the first and second outboard sections 18, 22 to move relative to the inboard section 16, thereby enabling the angle of attack of the airfoil 12 to be

modified for gust rejection. The airfoil 12 is thereby capable of smoother flight due to a

change in the angle of attack, reduced drag due to the curvature of a leading edge section 24

and improved wind gust rejection due to adaptive washout as a result of the airfoil 12

flexing, twisting and decambering.

As shown in Figures 1-4, the airfoil 12 may be formed from a leading edge section 24

extending generally from a first tip 26 to a second tip 28 that is generally opposite to the first

tip 26. The leading edge section 24 may be curved such that a bottom surface 30 forming a

pressure side 32 of the airfoil 12 forms a portion of a concave pressure side 32. The leading

edge section 24 may be bendable to enable the airfoil 12 to be easily stored in, for instance, a

tube or other structure. The leading edge section 24 may be configured to bend in a first

direction such that first and second tips 26, 28 of the leading edge section 24 may be bent

towards the pressure side 32 of the airfoil 12 but may not bend substantially in a second, generally opposite direction toward a suction side 34 of the airfoil 12. The camber formed

by the leading edge section 24 provides the airfoil 12 with the structural stability to substantially prevent airfoil 12 from bending upwardly when subjected to an upwardly

directed load. The airfoil 12 can be bent with a downward force applied to the suction side

34 but not with an upward force applied to the pressure side 32 because of the configuration

of the airfoil 12 and materials used to form the airfoil 12.

The airfoil 12 may have any appropriate overall shape. In at least one embodiment,

as shown in Figures 2-4, the airfoil 12 may include a relatively straight leading edge 36 in the

leading edge section 24 and may have a generally hemispherically shaped perimeter 38 forming a trailing edge 38 of the airfoil 12 extending from the first tip 26 to the second tip 28. The airfoil 12 is not limited to this configuration, but may have other appropriate

configurations as well. In at least one embodiment, the airfoil 12, as shown in Figure 2, may be formed from a single layer of material, and, in alternative embodiments, may be formed

from two or more layers of material. The airfoil 12 may be formed from resilient materials, such as, but not limited to: fiber reinforced laminates and fabrics, such as, carbon fiber

reinforced polymers, glass reinforced polymers, and aramid reinforced polymers; carbon fiber epoxy; foam materials; plastics, and other appropriate materials.

The airfoil 12 may include the inboard section 16 positioned between the first

outboard section 18 and the second outboard section 22 and extending from the leading edge 36 to the trailing edge 38. The trailing edge 38 of the inboard section 16 may or may not be

aligned with the trailing edge 38 of the first and second outboard sections 18, 22. In at least

one embodiment, the inboard section 16 may be rigidly coupled to the leading edge section

24. In another embodiment, the inboard section 16 and the leading edge section 24 may be a monolithic structure formed from a carbon fiber epoxy material, an aramid fiber/epoxy

mixture, or other appropriate lightweight material having sufficient flexibility and strength. The carbon fiber epoxy material may provide sufficient strength to absorb forces encountered

from wind gusts while maintaining a sufficiently light weight. The carbon fiber weave may

be a ^+"45 degree configuration. In another embodiment, the carbon fiber weave may be a zero degree/90 degree configuration. The inboard section 16 may also support a fuselage 40 of a micro air vehicle 42. The fuselage 40 may or may not house an engine capable of

providing rotational motion to a propeller 15. The engine may be, but is not limited to being,

one of many conventional engines used to power miniature aircraft. The fuselage 40 may be

configured to house a camera, which may be, but is not limited to being, a video camera, a still photography camera, or other audio or visual recording devices. A tail 44 may extend

from the fuselage 40 or the airfoil 12, or both for controlling the micro air vehicle 10. The tail 44 may be positioned generally orthogonal to the airfoil 12, as shown in Figure 1,

generally parallel to the airfoil 12 or in another position. Micro air vehicle 10 may include other components that are typically found on miniature aircraft. The tail 44 may extend from

the pressure side 32 of the suction side 34 of the airfoil 12, or both.

The airfoil 12 may also include a first compliant region 14 positioned between the

first outboard section 14 and the inboard section 16. The first compliant region 14 maybe

configured to enable the first outboard section 14 to move relative to the inboard section 16 so that the angle of attack of the airfoil 12 may be changed in response to the airfoil 12

encountering a wind gust. The first compliant region 14 may extend from the trailing edge 38 toward the leading edge 36, as shown in Figure 4. in one embodiment, the first compliant

region 14 may extend from the trailing edge 38 toward the leading edge 36 and terminate in close proximity with the leading edge section 24, as shown in Figure 3. In another

embodiment, the first compliant region 14 may extend from the trailing edge 38 toward the

leading edge 36 and terminate in contact with the leading edge section 24, as shown in

Figure 2. The first compliant region 14 may extend generally spanwise from the trailing

edge 38 toward the leading edge 36. In one embodiment, the first compliant region 14 may be generally orthogonal to the leading edge 36.

As shown in Figure 4, the airfoil 12 may include a flight tuning device 46 enabling the flight of the airfoil to be tuned. The airfoil 12 may be tuned by changing a length of the

first compliant region 14. The longer the first compliant region 14 is constructed, the more compliant the first outboard section 18 is when loaded during flight. The flight tuning device 46 may be any device capable of changing the effective length of the first compliant region

14. The effective length of the first compliant region 14 is defined as being the length along

which the first outboard section 18 is unrestrained relative to the adjacent inboard section 16. In at least one embodiment, the flight tuning device 46 may be a slidable fastener adapted to be attachable to the inboard section 16 and to the first outboard section 18 at different

positions along the length of the first compliant region 14. The fastener 46 may be adjusted

along the length of the second compliant region 20 in the direction shown by arrow 110.

In at least one embodiment, the first compliant region 14 may be a slot 48, as shown

in Figure 3, that extends from the trailing edge 38 toward the leading edge 36. The slot 48 may be sized to enable the first outboard section 18 to move relative to the inboard section

16 about the leading edge section 24. The leading edge section 24 may bend to enable the

movement of the first outboard section 18 relative to the inboard section 16. The width of the slot 48 may be sized to enable this movement yet not be so large that pressure equalization occurs across the airfoil 12 through the slot 48. Thus, the slot 48 may have a

width that is large enough to enable movement without restrictive friction between the first

outboard section 18 and the inboard section 16, yet small enough to limit pressure

equalization across the airfoil 12 through the slot 48.

A seal 50 may be positioned between the first outboard section 18 and the inboard

section 16 to limit pressure equalization through the slot 48, as shown in Figure 6. The seal 50 may be formed from any material capable of limiting pressure equalization through the

slot 48 without creating friction inhibiting movement of the first outboard section 18. In at

least one embodiment, the seal 50 may be formed from a flexible material, such as a feather, or other appropriate material. In another embodiment, the seal 50 may include an end plate 52, as shown in Figure

5, extending from the suction side 34 of the airfoil 12 proximate to the slot 48 for limiting pressure equalization through the slot 48. The end plate 52 may be positioned such that as

the first outboard section 18 moves relative to the inboard section 16, an inner edge 54 of the

first outboard section 18 moves in close proximity to the end plate 52 thereby maintaining a

small gap between the first outboard section 18 and the end plate 52. The end plate 52 may

also extend from the pressure side 32 of the airfoil 12.

In another embodiment, as shown in detail in Figure 7, the first compliant region 14

may be formed from a flexible material attached to the first outboard section 18 and attached to the inboard section 16, wherein a length of the material may be greater than a distance

between the first outboard section 18 and the inboard section 16, thereby permitting the first

outboard section 18 to bend about the leading edge section 24 relative to the inboard section

16. In such a configuration, the first compliant region 14 may be formed from a material, such as, but not limited to, latex, or other appropriate material enabling the first outboard

section 18 to move relatively unencumbered relative to the inboard section 16. The material

may prevent pressure equalization across the airfoil 12 through the first compliant region 14.

The second compliant region 20 may be formed in the same configurations as the first

compliant region 14, as set forth above. In particular, the second compliant region 20 may be positioned between the second outboard section 22 and the inboard section 16. The

second compliant region 20 may be configured to enable the second outboard section 22 to move relative to the inboard section 16 so that the angle of attack of the airfoil 12 maybe

changed in response to the airfoil 12 encountering a wind gust. The second compliant region

20 may extend from the trailing edge 38 toward the leading edge 36, as shown in Figure 4. In one embodiment, the second compliant region 20 may extend from the trailing edge 38

toward the leading edge 36 and terminate in close proximity with the leading edge section

24, as shown in Figure 3. In another embodiment, the second compliant region 20 may extend from the trailing edge 38 toward the leading edge 36 and terminate in contact with the leading edge section 24, as shown in Figure 2. The second compliant region 20 may extend

generally spanwise from the trailing edge 38 toward the leading edge 36. In one

embodiment, the second compliant region 20 may be generally orthogonal to the leading edge 36.

As shown in Figure 4, a flight tuning device 46 may enable the flight of the airfoil to

be tuned by changing a length of the second compliant region 20. The longer the second

compliant region 20 is constructed, the more compliant the second outboard section 22 is when loaded during flight. The flight tuning device 46 may be any device capable of

changing the effective length of the second compliant region 20. The effective length of the

second compliant region 20 is defined as being the length along which the second outboard

section 22 is unrestrained relative to the adjacent inboard section 16. In at least one

embodiment, the flight tuning device 46 may be a sidable fastener 46, as shown in Figure 4,

adapted to be attachable to the inboard section 16 and to the second outboard section 22 at

different positions along the length of the second compliant region 20. The fastener 46 may

be adjusted along the length of the second compliant region 20 in the direction shown by arrow 110.

In at least one embodiment, the second compliant region 20 may be a slot 56, as

shown in Figure 3, that extends from the trailing edge 38 toward the leading edge 36. The slot 56 may be sized to enable the second outboard section 22 to move relative to the inboard section 16 about the leading edge section 24. The leading edge section 24 may bend to

enable the movement of the second outboard section 22 relative to the inboard section 16. The width of the slot 56 may be sized to enable this movement yet not be so large that pressure equalization occurs across the airfoil 12 through the slot 56. Thus, the slot 56 may have a width that is large enough to enable movement without restrictive friction between the

second outboard section 22 and the inboard section 16, yet small enough to limit pressure

equalization across the airfoil 12 through the slot 56.

A seal 58 may be positioned between the second outboard section 22 and the inboard

section 16 to limit pressure equalization through the slot 56, as shown in Figure 6. The seal

58 may be formed from any material capable of limiting pressure equalization through the

slot 56 without creating friction inhibiting movement of the second outboard section 22. In

at least one embodiment, the seal 58 may be formed from a flexible material, such as a feather, or other appropriate material.

In another embodiment, as shown in Figure 7, the seal 58 may include an end plate

60, as shown in Figure 5, extending from the suction side 34 of the airfoil 12 proximate to the slot 56 for limiting pressure equalization through the slot 56. The end plate 60 may be positioned such that as the second outboard section 22 moves relative to the inboard section

16, an inner edge 62 of the second outboard section 22 moves in close proximity to the end

plate 62 thereby maintaining a small gap between the second outboard section 22 and the end

plate 62. The end plate 62 may also extend from the pressure side 32 of the airfoil 12.

In another embodiment, the second compliant region 20 may be formed from a

flexible material attached to the second outboard section 22 and attached to the inboard section 16, wherein a length of the material is greater than a distance between the second outboard section 22 and the inboard section 16, thereby permitting the second outboard

section 22 to bend about the leading edge section 24 relative to the inboard section 16. In such a configuration, the second compliant region 20 may be formed from a material, such as, but not limited to, latex, or other appropriate material enabling the second outboard section 22 to move relatively unencumbered relative to the inboard section 16. The material

may prevent pressure equalization across the airfoil 12 through the second compliant region 20.

The airfoil 12 may include one or more camber adjustable regions 64 capable of

changing camber in response to a wind gust. By changing camber, the airfoil 12 is able to fly

smoother than conventional airfoils without such compliant regions 64. The camber

adjustable regions 64 may form a portion of the pressure side 32 facing downward, wherein

the material improves wind gust rejection due to the changing camber and due to adaptive washout as a result of the material flexibly decambering, as shown in Figure 5 wherein the

material flexes toward the suction side 34. The airfoil 12 may include a first camber

adjustable region 66 positioned in the first outboard section 18 and a second camber

adjustable region 20 positioned in the second outboard section 22. The first and second camber adjustable regions 66, 68 may extend from the leading edge section 24 to the trailing

edge 38 and may form the trailing edge 38. The first and second camber adjustable regions

66, 68 may also extend from the first and second compliant regions 14, 20, to the first and

second tips 26, 28 of the airfoil 12, respectively. The first and second camber adjustable

regions 66, 68 may be supported by one or more battens 70, as shown in Figure 3, that are formed from a relatively rigid material to add structural support to the first and second camber adjustable regions 66, 68. In at least one embodiment, the battens 70 may be formed from the same material used to form the leading edge section 24.

In another embodiment, as shown in Figures 2, 4, 6, and 7, the airfoil 12 may also

include a first outboard section perimeter support structure 72 attached to a perimeter 74 of

the first outboard section 18. The first outboard perimeter support structure 72 may, in at

least one embodiment, extend from the first tip 26 of the airfoil 12 along the trailing edge 38

to a point 76 at an intersection between the trailing edge 38 and the first compliant region 14. The first outboard perimeter support structure 72 may extend along the intersection of the

first outboard section 18 and the first compliant region 14 from the trailing edge 38 toward the leading edge 36. In another embodiment, a batten 70 may be used to support the first

camber adjustable region 66 at the intersection between the first outboard section 18 and the first compliant region 14. The first outboard perimeter support structure 72 may be relatively thin in width sufficient to provide support yet not wide enough to inhibit decambering of the first camber adjustable region 66.

The airfoil 12 may also include a second outboard section perimeter support structure 78 attached to a perimeter 80 of the second outboard section 22. The second outboard

section perimeter support structure 78 may, in at least one embodiment, extend from the

second tip 28 of the airfoil 12 along the trailing edge 38 to a point 82 at an intersection

between the trailing edge 38 and the second compliant region 20. The second outboard perimeter support structure 78 may extend along the intersection of the second outboard section 22 and the second compliant region 20 from the trailing edge 38 toward the leading edge 36. In another embodiment, a batten 70 may be used to support the second camber

adjustable region 68 at the intersection between the second outboard section 22 and the second compliant region 20. The second outboard perimeter support structure 78 may be

relatively thin in width sufficient to provide support yet not wide enough to inhibit decambering of the second camber adjustable region 68.

In at least one embodiment, at least a portion of the airfoil 12 may be monolithic. In

particular, in one embodiment, the leading edge section 24 and the inboard section 16 may be

monolithic. The monolithic structure forming the leading edge section 24 and the inboard

section 16 may be formed from a carbon fiber epoxy material or other appropriate

lightweight material having sufficient flexibility and strength. The carbon fiber weave may

be a ^+"45 degree configuration. In another embodiment, the carbon fiber weave may be a

zero degree/90 degree configuration. In another configuration, the leading edge section 24, the inboard section 16, the first outboard section perimeter support structure 72, and the second outboard section perimeter support structure 78 may form a monolithic structure.

This monolithic structure may also be formed from a carbon fiber epoxy material or other appropriate lightweight material having sufficient flexibility and strength.

During use, the airfoil 12 operates to create lifting forces imparted on the pressure side 32 of the airfoil 12. Upon encountering a wind gust, the first and second compliant

regions 14, 20 may move upward, toward the suction side 34 relative to the inboard section

16. The first and second compliant regions 14, 20 may move upward by bending the leading

edge section 24 relative to the inboard section 16. This movement reduces the angle of

attack, thereby enabling the airfoil 12 to reject a wind gust. In addition, the first and second camber adjustable regions 66, 68 on the airfoil 12 may change their camber in response to a wind gust, as shown in Figure 5, as a result of the material that forms the first and second

camber adjustable regions 66, 68 flexing toward the suction side. After the gust has passed, the airfoil 12 returns to its original shape because of the elastic characteristics of the leading

edge section 24. These forces abate only when airfoil 12 is returned to its original position. The materials used to form the airfoil 12 have great flexibility and elasticity and bend rather

than yielding permanently.

The foregoing is provided for purposes of illustrating, explaining, and describing

embodiments of this invention. Modifications and adaptations to these embodiments will be apparent to those skilled in the art and may be made without departing from the scope or spirit of this invention.

Claims

CLAIMSWe claim:

1. An airfoil for a micro air vehicle, comprising:

a leading edge section extending from a first tip to a second tip;

an inboard section extending from the leading edge section toward a trailing edge of the airfoil;

a first outboard section extending from the leading edge section toward the trailing

edge of the airfoil and positioned on a first side of the inboard section;

a second outboard section extending from the leading edge section toward the trailing edge of the airfoil and positioned on a second side of the inboard section that is opposite to the first side;

at least one compliant region positioned between the first outboard section and the inboard section and extending from proximate the leading edge section to the trailing edge

enabling the first outboard section to move relative to the inboard section about the leading edge section; and

at least one compliant region positioned between the second outboard section and the

inboard section and extending from proximate the leading edge section to the trailing edge enabling the second outboard section to move relative to the inboard section about the leading edge section.

2. The airfoil for a micro air vehicle of claim 1, wherein the at least one compliant region positioned between the first outboard section comprises at least one slot

extending from proximate the leading edge section to the trailing edge.

3. The airfoil for a micro air vehicle of claim 2, further comprising a seal positioned between the first outboard section and the inboard section enabling the first

outboard section to move relative to the inboard section by bending about the leading edge

section while substantially preventing equalization of pressure from a pressure side to a

suction side of the airfoil through the at least one compliant region.

4. The airfoil for a micro air vehicle of claim 3, wherein the seal comprises an

end plate extending from a suction side of the airfoil proximate to the at least one slot for

limiting pressure equalization through the slot of the airfoil.

5. The airfoil for a micro air vehicle of claim 2, wherein the at least one slot positioned between the first outboard section and the inboard section comprises a slot

extending generally chordwise from the leading edge section to the trailing edge.

6. The airfoil for a micro air vehicle of claim 1, wherein the at least one

compliant region comprises material attached to the first outboard section and attached to the inboard section, wherein a length of the material is greater than a distance between the first

outboard section and the inboard section, thereby permitting the first outboard section to

move about the leading edge section relative to the inboard section.

7. The airfoil for a micro air vehicle of claim 6, wherein the at least one compliant region comprises material attached to the second outboard section and attached to

the inboard section, wherein a length of the material is greater than a distance between the

second outboard section and the inboard section, thereby permitting the second outboard

section to move about the leading edge section relative to the inboard section.

8. The airfoil for a micro air vehicle of claim 2, wherein the at least one

compliant region positioned between the second outboard section comprises at least one slot extending from proximate the leading edge section to the trailing edge.

9. The airfoil for a micro air vehicle of claim 8, further comprising a seal positioned between the second outboard section and the inboard section enabling the second

outboard section to move relative to the inboard section by bending about the leading edge section while substantially preventing equalization of pressure from a pressure side to a suction side of the airfoil through the at least one compliant region.

10. The airfoil for a micro air vehicle of claim 9, wherein the seal between the

second outboard section and the inboard section comprises an end plate extending from a suction side of the airfoil proximate to the at least one slot for limiting pressure equalization through the slot of the airfoil.

11. The airfoil for a micro air vehicle of claim 8, wherein the at least one slot

positioned between the second outboard section and the inboard section comprises a slot

12. The airfoil for a micro air vehicle of claim 1 , further comprising a first camber

adjustable region forming at least a portion of the first outboard section and formed from at

least one layer of a flexible material that includes a camber forming a concave surface facing

downward and improves wind gust rejection due to adaptive washout as a result of the

material flexibly decambering.

13. The airfoil for a micro air vehicle of claim 12, further comprising a second

camber adjustable region forming at least a portion of the second outboard section and

formed from at least one layer of a flexible material that includes a camber forming a concave surface facing downward and improves wind gust rejection due to adaptive washout

as a result of the material flexibly decambering.

14. The airfoil for a micro air vehicle of claim 12, wherein the first camber

adjustable region includes one or more battens extending from the leading edge section toward the trailing edge and is attached to the at least one layer of a resilient, flexible material.

15. The airfoil for a micro air vehicle of claim 14, wherein the second camber adjustable region includes one or more battens extending from the leading edge section toward the trailing edge and is attached to the at least one layer of a resilient, flexible

material.

16. The airfoil for a micro air vehicle of claim 13, further comprising a first outboard section perimeter support structure positioned at the perimeter of the first outboard

section and attached to the leading edge section.

17. The airfoil for a micro air vehicle of claim 16, further comprising a second

outboard section perimeter support structure positioned at the perimeter of the first outboard section and attached to the leading edge section.

18. The airfoil for a micro air vehicle of claim 17, wherein the leading edge

section, the inboard section, the first outboard section perimeter support structure, and the second outboard section perimeter support structure comprise a monolithic structure.

19. The airfoil for a micro air vehicle of claim 13, wherein the flexible material

comprising the first and second camber adjustable regions is latex.

20. The airfoil for a micro air vehicle of claim 1 , wherein the leading edge section is formed from a carbon fiber epoxy.

21. The airfoil for a micro air vehicle of claim 1 , further comprising a flight tuning device in communication with the at least one compliant region positioned between the first outboard section and the inboard section for changing an effective length of the at least one

compliant region positioned between the first outboard section and the inboard sections to

tune flight characteristics of the airfoil.

22. An airfoil for a micro air vehicle, comprising:

a leading edge section extending from a first tip to a second tip;

edge of the airfoil and positioned on a first side of the inboard section;

a second outboard section extending from the leading edge section toward the trailing

edge of the airfoil and positioned on a second side of the inboard section that is opposite to the first side;

at least one compliant region positioned between the first outboard section and the

inboard section and extending from proximate the leading edge section toward the trailing

edge enabling the first outboard section to move relative to the inboard section by bending about the leading edge section;

edge enabling the second outboard section to move relative to the inboard section by bending about the leading edge section;

a first outboard perimeter support structure positioned at a perimeter of the first outboard section and attached to the leading edge section; and a second outboard perimeter support structure positioned at a perimeter of the second

outboard section and attached to the leading edge section.

23. The airfoil for a micro air vehicle of claim 22, wherein the leading edge

section, the inboard section, the first outboard perimeter support structure, and the second

outboard perimeter support structure comprise a monolithic structure.

24. The airfoil for a micro air vehicle of claim 23, wherein the monolithic structure is formed from a carbon fiber epoxy.

25. The airfoil for a micro air vehicle of claim 22, wherein the at least one

compliant region positioned between the first outboard section comprises at least one slot extending from proximate the leading edge section to the trailing edge.

26. The airfoil for a micro air vehicle of claim 25, further comprising a seal

positioned between the first outboard section and the inboard section enabling the first outboard section to move relative to the inboard section by bending about the leading edge section while substantially preventing equalization of pressure from a pressure side to a

suction side of the airfoil through the at least one compliant region.

27. The airfoil for a micro air vehicle of claim 26, wherein the seal comprises an

end plate extending from a suction side of the airfoil proximate to the at least one slot for limiting pressure equalization through the slot of the airfoil.

28. The airfoil for a micro air vehicle of claim 25, wherein the at least one slot positioned between the first outboard section and the inboard section comprises a slot

29. The airfoil for a micro air vehicle of claim 22, wherein the at least one

compliant region comprises material attached to the first outboard section and attached to the

inboard section, wherein a length of the material is greater than a distance between the first outboard section and the inboard section, thereby permitting the first outboard section to

move relative to the inboard section by bending about the leading edge section.

30. The airfoil for a micro air vehicle of claim 22, wherein at least a portion of the first outboard section is formed from at least one layer of a flexible material that includes a camber forming a concave surface facing downward and improves wind gust rejection due to

adaptive washout as a result of the material flexibly decambering; and wherein at least a portion of the second outboard section is formed from at least one layer of a flexible material

includes a camber forming a concave surface facing downward, and improves wind gust

rejection due to adaptive washout as a result of the material flexibly decambering.

31. The airfoil for a micro air vehicle of claim 30, wherein the first outboard section includes one or more battens extending from the leading edge section toward the trailing edge and is attached to the flexible material of the first camber adjustable region, and

wherein the second outboard section includes one or more battens extending from the leading edge section toward the trailing edge and is attached to the flexible material of the second

camber adjustable region.

32. The airfoil for a micro air vehicle of claim 31, wherein the flexible material

comprising the first and second camber adjustable regions is latex.