Transformable wing of unmanned aerial vehicle

Abstract

FIELD: aerodynamics.SUBSTANCE: invention can find application in aviation technology, for example, in the designs of transformable bearing surfaces of adaptive wings, providing a given smooth change in wing geometry. The transformable wing of an unmanned aerial vehicle consists of a fixed part and a movable part, which, when folded, is located inside the fixed part. The line of the central axis of the moving part coincides with the line of the central axis of the fixed part. In this case, both the fixed part and the end of the movable part have a tapering shape so that the movable part, when folded, corresponds to the fixed part.EFFECT: improved performance.1 cl, 3 dwg

Description

[0001] The invention relates to the field of aerodynamics and can find application in aviation technology, for example, in the designs of a transformable bearing surface of adaptive wings, providing a given smooth change in the geometry of the wing.

[0002] Over the past few decades, numerous studies have been conducted on the idea of ​​morphing. These studies have focused on the advantages of morphing technology for variable-span wings, based on the impact of increased lift-to-drag ratio on performance and maneuverability. Most of these studies have focused on the design and study of telescopic mechanisms with rectangular wings at zero yaw rate.

[0003] The main advantage of deformed wing technology over conventional fixed wing designs is the ability to optimize the aerodynamic profile throughout the flight, resulting in significant benefits in aerodynamic performance, flight envelope, vibration and flutter elimination, low observability, and control efficiency. A device known is an aerodynamic wing of an aircraft with an adaptively variable surface. The aerodynamic wing with an adaptively variable surface for turbulence compensation contains movable plates that have two axes of rotation, supported by elements of the wing frame. The frame is rigid and fixed, consisting of rows of load-bearing spars, onto which rows of ribs are placed. Cover plates in the shape of regular polygons are attached to the ribs using a rotary joint [1].

[0004] A known design for an elastically deformable panel capable of assuming a given shape. It comprises a movable frame to which one edge of a flexible skin is rigidly attached, also having movable rod-shaped point supports. The other edge of the skin is movable [2].

[0005] An adaptive wing is known [3] comprising a frame which has an upper elastically variable part and a lower elastically variable part connected on the inside by lever elements, an adapter connecting the upper elastically variable part with a support element to which an actuator for translational motion is attached.

[0006] The disadvantages of these analogs are the use of a fully flexible skin on the trailing edge of the wing and the associated need to use a large number of internal support elements.

[0007] Another disadvantage of the prototype is the redundancy of independent power drives for deflecting the airfoil links, which generally increases the weight of the adaptive wing. In addition, due to the use of elastomer panels, undamped mechanical loads arise in the power drive, which reduces its service life and reliability.

[0008] The aim of the transformable wing unmanned aerial vehicle invention is to enable the UAV to perform its missions in various flight conditions, increasing the performance and improving the controllability and maneuverability of the aircraft.

[0009] The stated problem is solved due to the fact that in the transformable wing of the unmanned aerial vehicle, consisting of a fixed part, according to the invention, a movable part is additionally introduced, which in the folded state is located inside the fixed part, and the line of the central axis of the movable part coincides with the line of the central axis of the fixed part, while both the fixed part and the end of the movable part have a tapering shape so that the movable part in the folded state corresponds to the fixed part.

[0010] The features that distinguish the proposed transformable wing from known ones are that a movable part is additionally introduced, which in the folded state is located inside the fixed part, and the line of the central axis of the movable part coincides with the line of the central axis of the fixed part, while both the fixed part and the end of the movable part have a tapering shape so that the movable part in the folded state corresponds to the fixed part.

[0011] The ability to change the wing aspect ratio allows the drone to smoothly perform its mission at various stages of flight. Furthermore, this allows the drone to improve its aerodynamic performance and fuel efficiency. For example, longer spans have led to significant improvements in aerodynamic performance and fuel efficiency. However, they also reduce maneuverability and limit cruising speeds. Conversely, wings with a low aspect ratio provide greater maneuverability and increase aircraft speed, but reduce flight performance and increase fuel consumption.

[0012] The mainly transforming wing idea can be divided into three main types as follows.

[0013] Change in plan shape:

[0014] In this type of wing, the dimensions of its shape, such as span, chord length and sweep angle, can be changed.

[0015] Out-of-plane transformation:

[0016] The out-of-plane transformation of the wing is mainly based on three parameters, which include spanwise camber, chordwise camber and wing twist.

[0017] Aerodynamic profile adjustment:

[0018] The adjustment of the airfoil is mainly influenced by two parameters: changing the curvature and thickness, which can change the shape of the airfoil.

[0019] With the growing use of UAVs in various civil and military applications, the field of transformative aviation technology will play a significant role in the coming periods.

[0020] The morphing ideology provides huge advantages such as:

[0021] Increasing flight range by improving aerodynamic efficiency.

[0022] Perform multiple tasks to achieve fundamentally new maneuvers without using traditional controls.

[0023] Reduces drag force to improve fuel efficiency, resulting in expanded flight limits.

[0024] Reduce vibration and flutter by improving design capabilities.

[0025] The variable-span wing provides excellent multi-tasking capability. By varying its span and aerodynamic surface, the wing more effectively addresses a variety of tasks than a conventional wing, including cruising, hovering, long-range flight, maneuverability, and control. Another advantage of the variable-span wing is roll control through asymmetric wing changes, rather than conventional control surfaces. Asymmetric wing loading helps coordinate yaw and roll movements.

[0026] Large-wingspan aircraft have good aerodynamic efficiency, which translates into greater range and fuel economy. Conversely, aircraft with reduced wingspans are faster and more maneuverable. Therefore, the variable-span concept offers a good way to achieve the advantages of both designs. The proposed patent application is based on the relationship between increased wingspan, range, and fuel efficiency.

[0027] Furthermore, this application examines the effect of an asymmetric wing span strategy on roll control. It also demonstrates the effect of varying the wing sweep angle on aircraft performance. The wing is divided into a fixed segment and a variable segment. The fixed segment is the basic wing without modifications. The variable segment consists of an inner segment that can slide, changing the sweep angle.

[0028] Fig. 1, 2, 3 schematically depict a transformable wing of an unmanned aerial vehicle.

[0029] Fig. 1. Shows the change in wing geometry of two models (a), (c): the first model with a sweep angle (b), (d): the second model with a sweep angle in the initial position and at full extension.

[0030] Fig. 2 shows the variable span of the tapered transforming wings for (a): the first sweep angle model and (b): the second sweep angle model.

[0031] Fig. 3 schematically shows the increase in wing span,

[0032] where:

[0033] 1 - fixed wing,

[0034] 2 - inner wing,

[0035] 3 - fixed wing sweep angle,

[0036] 4 - inner wing sweep angle,

[0037] 5 - wing length in the initial position and at full span.

[0038] In Fig. 1, a fixed wing 1 with a length, for example, bi of the wing in the initial position and at full span, and an angle 3, for example α of sweep of the fixed section, contains an inner wing 2 and an angle 4, for example β - the sweep angle of the inner section extending from the fixed wing 1.

[0039] The inner wing has a sweptback geometric shape to match its position on a fixed-wing aircraft. The inner wing tip has a tapered wing shape to match the fixed wing in its original position.

[0040] Figure 2 shows two wing configurations for two different sweep angles of their inner sections β1 and β2. The first design configuration shows the central axis line of the movable segment coincident with the central axis line of the fixed wing. The second design configuration shows the leading edge of the movable segment located parallel to the leading edge of the fixed segment.

[0041] The half-span of one side is increased to the desired distance y1 while keeping the other side stationary, as shown in Fig. 3.

[0042] It is expected that asymmetrical control of a variable-span wing will produce a roll moment that would otherwise be achieved with conventional ailerons. However, the difficulty with this method lies in the significant bending moment exerted on the wing root. The bending moment of a variable-span wing increases as the product of the lift distribution, wing area, wing panel span, and free-flow dynamic pressure increases due to the increase in span. Weight is also a significant factor influencing the increase in bending moment, especially if the auxiliary actuator is located at the wing root. According to some studies, the bending moment at the root of a variable-span wing can be 60% higher than that at the root of a wing with conventional ailerons.

[0043] The total lift at the start of a roll can be defined as:

[0044]

[0045] where L is the lift force generated by the original wing, ΔL is the lift force arising from the increase in span, q is the dynamic pressure, C L is the lift coefficient, S is the original wing area, and ΔS is the additional wing area after increasing the span. The lift is equal on both sides of the wing due to its symmetrical span. However, since the wing area changes on one side due to an asymmetric increase or decrease in span, the lift on one side of the wing will be greater.

[0046] The area S of the tapered wing and the changing area ΔS of the geometric shape of the variable sweep wing become:

[0047]

[0048] where b is the span of the original wing, c r - chord at the base, c t - chord at the end.

[0049] The changing area is located:

[0050]

[0051] Where y1 is the additional wing span after increasing the span, c r - chord at the base, c t - chord at the end.

[0052] The overall lift coefficient can be found using the following equation.

[0053]

[0054] Roll moment L roll can be approximately calculated using the following equation:

[0055]

[0056] According to the assumption underlying the equation, the lift force acts at the midpoint of the wing aspect ratio, so its lever arm is equal to ((b / 2)+(y 1 / 2)). Substituting equation (4) into the roll moment equation (5), we obtain equation (6):

[0057]

[0058] where L roll - the moment of overturning, L is the lift in the initial position, and ΔL is the lift obtained by increasing the span.

[0059] Equation (6) shows that when the wing is extended on one side, the roll moment created depends on the difference between the lift created at both half-spans.

[0060] Asymmetric span configurations can alter the lift distribution in a convertible wing. For example, when one side of the wing (right or left) has a longer span than the other, the symmetrical lift distribution point shifts toward the side with the longer span. The resulting roll moment is expected to be the same as when deflecting conventional ailerons for roll control. For pure roll caused by the change in mass moment of inertia, the first-order equation can be defined as:

[0061]

[0062] Where Ixx is the moment of inertia about the x-axis, and p is the bank angle. Assuming uniform wing mass distribution and ignoring the contributions of other components such as the fuselage and empennage, the equation for the moment of inertia about the x-axis takes the following form:

[0063]

[0064] where mw is the wing mass. The moment of inertia of a variable-span wing can be expressed as follows:

[0065]

[0066] Ixxs is the moment of inertia of a variable-span wing relative to the x-axis, with y1 and y2 being the aspect ratios on the starboard and port sides, respectively. In the previous equations, the moment of inertia of the fuselage and empennage is ignored. Therefore, the rate of change of the wing's inertia is time-dependent and is defined as:

[0067]

[0068] Based on equation (7), the torque equation for span length change can be defined as:

[0069]

[0070] where (∂L / ∂y1)y1+(∂L / ∂y2)y2 are the roll moment due to the aspect ratio of the right and left wings, respectively, and (∂L / ∂p)p is the roll damping moment. To reduce the bending moment at the wing root, it is necessary to determine the corresponding aspect ratios of both sides of the wing under given flight conditions. Thus, the fundamental equation of roll motion becomes

[0071]

[0072] where

[0073]

[0074] and

[0075]

[0076] where Clps is the rolling moment damping coefficient.

[0077] The stable roll rate is determined by:

[0078]

[0079] and

[0080]

[0081] The time constant τ s is the response time in the roll mode, where the time constant can be defined as:

[0082]

[0083] The roll rate of a variable span wing in steady state is:

[0084]

[0085] The effectiveness of the transformable wing was also evaluated in terms of increased range and endurance. As the wing span increases, the aerodynamic performance (lift-to-drag ratio) improves, contributing to increased range and endurance and increased aircraft efficiency. To study this efficiency improvement, the geometric characteristics of a real aircraft were considered.

[0086] The range and duration of flight under the condition of horizontal flight according to Breguet formulas are:

[0087]

[0088]

[0089] Where R and E are the flight range and endurance, η, c, W0, and W1 are the specific thrust, fuel consumption, takeoff weight, and landing weight, respectively. For a specific transformable aircraft, the values ​​of speed and mass are constant in equations (19) and (20).

[0090] Please note that for a given altitude and weight, the flight range and flight duration are maximum when And are maximum. Their maximum values ​​are determined by the following equations:

[0091]

[0092]

[0093] Where e is the span efficiency coefficient, and C D0 is the drag coefficient at zero lift.

[0094] Aerodynamic efficiency depends on wing aspect ratio. As a result, increasing wing aspect ratio will lead to increased range and endurance. Moreover, flight endurance with a variable wing is further increased because the wing area also increases with aspect ratio. Numerical analysis methods used in this claimed device, using ANSYS Fluent, demonstrated the high efficiency of the claimed invention. Thus, the modeling results provide a clear understanding of the advantages of a variable wing for increasing range and endurance. The claimed invention can be implemented, for example, using rocker or cam mechanisms using pushers made of composite materials, as well as using a rolling or sliding structure.

[0095] Variable span wings with variable geometry are an effective technology for increasing aerodynamic efficiency and replacing traditional control surfaces. Improved flight performance leads to increased range and endurance.

[0096] Sources of information

[0097] 1. Patent RU No. 2660191.

[0098] 2. US Patent No. 3716209.

[0099] 3. US Patent No. 7384016 - prototype.

Claims

A transformable wing of an unmanned aerial vehicle, consisting of a fixed part, characterized in that a movable part is additionally introduced, which in the folded state is located inside the fixed part, wherein the line of the central axis of the movable part coincides with the line of the central axis of the fixed part, and both the fixed part and the end of the movable part have a tapering shape so that the movable part in the folded state corresponds to the fixed part.

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