D-truss wing structure for unmanned aerial vehicles.

Abstract

This paper deals with D-truss wing structures for unmanned aerial vehicles. [Solution] The system, device and method include a leading edge tubular member (114), an upper tubular member (110), a lower tubular member (112), one or more upper rib members connected between the leading edge tubular member (114) and the upper tubular member (110), one or more lower rib members connected between the leading edge tubular member (114) and the lower tubular member (112), a rigid sandwich shell (102) disposed between the upper tubular member (110) and the leading edge tubular member (114), and a sandwich shear web (104) disposed between the upper tubular member (110) and the lower tubular member (112), wherein the rigid sandwich shell (102) and the sandwich shear web (104) form a D-shape.

Description

[Technical Field]

[0001] The present embodiments relate generally to wing structures, and more particularly to D-truss wing structures for unmanned aerial vehicles.

[0002] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to and the benefit of U.S. Provisional Patent Application No. 62 / 970,827, filed February 6, 2020, the contents of which are incorporated herein by reference for all purposes. [Background technology]

[0003] An aircraft may include one or more wings to maintain level flight. The wings may be subjected to various loads during flight. If not handled properly, these loads may damage the wings or adversely affect the lifespan of the aircraft. Aircraft may be manned or unmanned. Manned aircraft may be controlled by a pilot. Unmanned aerial vehicles (UAVs) may be remotely controlled by an operator and / or autonomously controlled by a processor. Summary of the Invention

[0004] An embodiment of the system can include a leading edge tubular member, an upper tubular member, a lower tubular member, one or more upper rib members connected between the leading edge tubular member and the upper tubular member, one or more lower rib members connected between the leading edge tubular member and the lower tubular member, a rigid sandwich shell disposed between the upper tubular member and the leading edge tubular member, and a sandwich shear web disposed between the upper tubular member and the lower tubular member, wherein the rigid sandwich shell and sandwich shear web form a D-shape.

[0005] In additional system embodiments, the leading edge tubular member, the upper tubular member, and the lower tubular member support all bending loads. In additional system embodiments, the rigid sandwich shell includes one or more expansion joints. In additional system embodiments, each expansion joint extends between the leading edge tubular member and the upper tubular member.

[0006] Additional system embodiments can further include a polyvinyl fluoride (PVF) film covering the system except for the rigid sandwich shell 102, the PVF film providing the airfoil shape. In additional system embodiments, the PVF film covers one or more channels formed by one or more expansion joints. In additional system embodiments, the rigid sandwich shell includes two thin composite face sheets separated by a low density core. In additional system embodiments, the two thin composite face sheets include carbon fiber and epoxy. In additional system embodiments, the low density core includes foam. In additional system embodiments, the low density core includes honeycomb.

[0007] Additional system embodiments can include one or more cross brace members coupled between each of the one or more lower rib members, wherein each of the one or more cross brace members is configured to pull the lower tubular member toward the leading edge tubular member.

[0008] Another system embodiment may include a leading edge tubular member, an upper tubular member, one or more upper rib members connected between the leading edge tubular member and the upper tubular member, and a rigid sandwich shell disposed between the upper tubular member and the leading edge tubular member.

[0009] Additional system embodiments may include a lower tubular member. Additional system embodiments may include one or more lower rib members coupled between the leading edge tubular member and the lower tubular member. Additional system embodiments may include a sandwich shear web disposed between the upper tubular member and the lower tubular member. In additional system embodiments, the rigid sandwich shell and the sandwich shear web form a D-shape. In additional system embodiments, the leading edge tubular member, the upper tubular member, and the lower tubular member support all bending loads. In additional system embodiments, the rigid sandwich shell includes one or more expansion joints. In additional system embodiments, each expansion joint extends between the leading edge tubular member and the upper tubular member. [Brief explanation of the drawings]

[0010] The components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the present invention. Like numerals refer to corresponding parts throughout the various views. Embodiments are illustrated by way of example and not by way of limitation in the accompanying drawings. [Figure 1] FIG. 1 shows a bottom perspective view of the D-truss wing structure of the unmanned aerial vehicle. [Figure 2] FIG. 2 shows a top perspective view of the rigid shell of the D-truss wing structure of FIG. [Figure 3] FIG. 3 shows a top perspective view of the D-truss wing structure of FIG. 1 with the rigid shell of FIG. 2 removed. [Figure 4] FIG. 4 shows a cutaway side cross-sectional perspective view of the upper tubular truss rib member of the D-truss wing structure taken along line AA in FIG. [Figure 5] FIG. 5 shows a cutaway cross-sectional view of the upper tubular truss rib member of FIG. [Figure 6] FIG. 6 shows a side view of a wing including a D-truss wing structure for an unmanned aerial vehicle. DETAILED DESCRIPTION OF THE INVENTION

[0011] FIG. 1 illustrates a D-truss wing structure 100 for a wing panel of an unmanned aerial vehicle (UAV). For reference, the thickness 101 of the elements of the D-truss wing structure 100 is shown. While the D-truss wing structure 100 is illustrated and described with respect to a UAV, in some embodiments, it can also be used with other aircraft. A UAV is an aircraft without an onboard pilot and can fly autonomously or remotely. In one embodiment, the UAV is a high-altitude, long-endurance aircraft. In one embodiment, the UAV can have one or more motors, e.g., 1 to 40 motors, and a wingspan of 100 to 400 feet. In one embodiment, the UAV can have a wingspan of approximately 260 feet and can be propelled by multiple motors, e.g., multiple propellers coupled to 10 electric motors, driven by solar arrays covering the wing surface, thereby achieving zero emissions. The UAV is designed to fly above the clouds at altitudes of approximately 65,000 feet above sea level and conduct continuous, long-term missions of up to several months without landing.

[0012] UAVs function optimally at high altitudes and are capable of sustained flight for significant periods without resorting to landing. In one embodiment, the UAV may weigh approximately 3,000 pounds.

[0013] The D-truss wing structure 100 includes a rigid sandwich shell 102 wrapped around a leading edge 106, a sandwich shear web 104, an upper tubular truss rib member (124, FIG. 3), a lower tubular truss member (126, FIG. 3), and one or more lightweight cross brace members 108. The wing structure 100 may further include an upper tubular member 110, a lower tubular member 112, and a leading edge tubular member 114, which function as spar caps and support all bending loads. The three spanwise extending tubes are the "caps." The tubular caps 134A, 134B, 134C may include a first tubular cap 134A, a second tubular cap 134B, and a third tubular cap 134C. In one embodiment, the tubular members 110, 112, 114 have a small diameter relative to the thickness of the airfoil and / or the height of the shear web 104. In one embodiment, the diameter and wall thickness of the tubular members can be optimized to resist buckling under all bending loads with minimal weight. In one embodiment, the diameter of the tubular members can be on the order of one-tenth the height of the sandwich shear web 104. In one embodiment, the sandwich shear web 104 can include a primary shear web 136 with a ¼-inch thick core. In one embodiment, the upper tubular member 110 can have a material thickness of approximately 0.337 to 0.360 inches. In one embodiment, the lower tubular member 112 can have a material thickness of approximately 0.266 to 0.291 inches. In one embodiment, the forward tubular member 114 can have a material thickness of approximately 0.177 to 0.199 inches. The tubular members 110, 112, and 114 can support all bending loads and are continuous across the length of the separable wing panel. A number of wing panels (e.g., seven wing panels) are connected end-to-end to form a complete wing. More specifically, the upper tubular member 110, the lower tubular member 112, and the leading edge tubular member 114 may be positioned at the three poles of the "D" shape formed by the leading edge 106 and the sandwich shear web 104 to carry all bending loads. In some embodiments, the leading edge 106 may include a leading edge shell 138 having a 3 / 16 inch thick core.The shear web 104 is essentially perpendicular to the chord plane, which extends from the leading edge to the trailing edge of the wing. The chord plane is angled relative to the ground by the wing's angle of attack in horizontal flight. A typical angle of attack for an aircraft having the disclosed D-truss wing structure 100 may be 10 to 12 degrees at leading edge height. Shear between the tubular members 110, 112, 114 may be supported by the sandwich shear web 104 between the upper tubular member 110 and the lower tubular member 112, the rigid sandwich shell 102 between the upper tubular member 110 and the leading edge tubular member 114, and the lightweight cross brace 108 between the lower tubular member 112 and the leading edge tubular member 114. In one embodiment, the rigid sandwich shell 102 may have a material thickness of approximately 0.177 inches to 0.199 inches, and the shear sandwich web 104 may have a material thickness of approximately 0.245 inches to 0.266 inches. In some embodiments, the scope of the disclosure may be broadened to accommodate aircraft having 1-40 motors and / or spans of 100-400 feet.

[0014] FIG. 2 illustrates a rigid sandwich shell 102. In one embodiment, the rigid sandwich shell 102 supports a sheet. In one embodiment, the rigid sandwich shell 102 can have multiple expansion joints 122A, 122B. Each expansion joint 122A, 122B can extend from the leading edge of the sandwich edge shell 114 to the aft end of the rigid sandwich shell 102 at the top tubular member 110. In one embodiment, the expansion joints 122A, 122B enable the rigid sandwich shell 102 to handle "spanwise" expansion and contraction associated with bending and also enable the rigid sandwich shell 102 to support in-plane and torsional shear. In some embodiments, the expansion joints 122A, 122B provide spanwise expansion and contraction while still supporting shear. Additionally, the rigid sandwich shell 102 can stabilize the top tubular member 110 and the leading edge tubular member 114. The rigid sandwich shell 102 can also maintain the shape of the airfoil. In one embodiment, all elements in FIG. 1 can be made from composite materials such as carbon fiber and epoxy. In some embodiments, the sandwich shell 102 can be made from a non-conductive material such as Kevlar (aramid) or fiberglass to avoid electrical shorting of the solar array. The rigid sandwich shell 102 and sandwich shear web 104 can be made from two thin composite face sheets separated by a low-density core. The composite material can be made from carbon fiber and epoxy. In other embodiments, the composite material can be made from Kevlar or fiberglass. The low-density core can be made from either foam or honeycomb. This combination provides high bending stiffness with minimal weight. In one embodiment, a polyvinyl fluoride (PVF) film, such as Tedlar film, covers the wing structure 100 (except for the rigid sandwich shell 102) to provide an airfoil shape. In other embodiments, a non-structural material can be used to cover the wing structure 100 (except for the rigid sandwich shell 102) to provide an airfoil shape.In one embodiment, Tedlar film can be used to cover the channels formed by expansion joints 122A, 122B. In another embodiment, tape with elastic properties can be used to cover the channels formed by expansion joints 122A, 122B.

[0015] In one embodiment, the rigid sandwich shell 102 can have a substantially hard, smooth molded surface to allow direct bonding of the solar cell module. In one embodiment, the face sheet material of the rigid sandwich shell 102 can be made of Kevlar and epoxy to make it non-conductive.

[0016] As shown in Figure 3, the rigid sandwich shell 102 has been removed to reveal that the upper tubular member 110, the lower tubular member 112, and the leading edge tubular member 114 are held in position relative to one another. More specifically, a plurality of upper rib members 124 are connected to the upper tubular member 110 and the leading edge tubular member 114. In one embodiment, the upper rib members 124 are connected to the upper tubular member 110 and the leading edge tubular member 114 and hold them in position relative to one another. Additionally, a plurality of lower rib members 126 are connected to the lower tubular member 112 and the leading edge tubular member 114.

[0017] As shown in FIG. 4, the upper rib member 124 supports the rigid sandwich shell (102, FIG. 2) via small webs 130 connected to the expansion joints. The lower rib member (126, FIG. 3) reacts to the cross brace tension load. More specifically, the cross brace member (108, FIG. 3) supports only tension loads because it may buckle under compression loads. Therefore, the cross brace member (108, FIG. 3) acts to pull the lower tubular member (112, FIG. 3) and the forward tubular member (114, FIG. 3) toward each other. In this case, the compressively loaded lower rib member (126, FIG. 3) keeps the lower tubular member (112, FIG. 3) and the forward tubular member (114, FIG. 3) apart. In one embodiment, each expansion joint 122A forms an expansion channel 402. In one embodiment, the upper rib member 124 is a massive truss member.

[0018] As shown in FIGS. 2 and 3 , in one embodiment, the interconnection of the upper rib member 124, the lower rib member 126, the tubular members 110, 112, and 114, the rigid sandwich shell 102 wrapped around the leading edge 106, and the sandwich shear web 104 generally form a D-shape. The “D” shape does not necessarily include the shell between the leading edge tubular member 114 and the lower tubular member 112. Thus, each D-truss wing structure 100 may have a series of so-called “D-truss” structures 128. In one embodiment, the upper rib member 124 and the lower rib member 126 may have a material thickness of approximately 0.038 inches to 0.062 inches. In one embodiment, the upper rib member 124, the lower rib member 126, and the tubular members 110, 112, and 114 may be made of carbon fiber.

[0019] For further clarity, a cutaway cross-sectional view of the upper tubular truss rib member 124 of Figure 4 is shown in Figure 5. One or more expansion joints 122A are provided in the rigid sandwich shell 102 adjacent to the upper tubular truss rib member 124. Small webs 130 connect the rib member 124 to the one or more expansion joints 122A.

[0020] Returning to FIG. 3 , lightweight cross brace members 108 are also shown. In one embodiment, the lightweight cross brace members 108 complete the torsional load path across the bottom of the D-truss wing panel structure (100, FIG. 2). In one embodiment, the lightweight cross brace members 108 can be installed without any provision for adjusting tension, thereby effectively providing zero preload on the lightweight cross brace members 108. In one embodiment, the lower rib members 126 can support batteries for operating the UAV, and a battery support structure 132 may replace the lightweight cross brace members 108. In one embodiment, the battery support structure 132 may be a plate or box that occupies the area in the rib bay (e.g., the space between adjacent ribs) that would be occupied by a pair of cross brace members 108 in the absence of the battery support structure. The battery plate or box 132 may have sufficient strength to support the loads normally experienced by the cross brace members 108. The batteries may occupy only a small portion of the total number of rib bays (e.g., 22 of 148 rib bays in one embodiment), with the remaining rib bays still having cross brace members 108. In one embodiment, the D-truss wing panel structure (100, FIG. 2) may include one or more tubular truss members 140, 142. In one embodiment, the D-truss wing panel structure (100, FIG. 2) may include a cross brace 144 for torsion.

[0021] 6 shows a side view of a wing 600 including the D-truss wing structure 100 for an unmanned aerial vehicle. The wing 600 can include a sandwich shell 102 between the leading edge tubular member 114 and the upper tubular member 110, a sandwich shear web 104 disposed between the upper tubular member 110 and the lower tubular member 112, a first plastic film skin 602 on the upper surface of the wing 600, and a second plastic film skin 604 on the lower surface of the wing 600. In one embodiment, a polyvinyl fluoride (PVF) film, such as Tedlar film, covers the wing 600 (except for the rigid sandwich shell 102) to provide the airfoil shape. In other embodiments, a non-structural material can be used to cover the wing 600 (except for the rigid sandwich shell 102) to provide the airfoil shape.

[0022] It is contemplated that various combinations and / or subcombinations of the specific features and aspects of the above-described embodiments may be made and still fall within the scope of the present invention. Thus, it should be understood that various features and aspects of the disclosed embodiments can be combined with or substituted for one another in order to form varying modes of the disclosed invention. Furthermore, it is intended that the scope of the present invention, although disclosed herein by way of example, should not be limited by the specific disclosed embodiments described above.

Claims

1. a leading edge tubular member (114); an upper tubular member (110); a lower tubular member (112); one or more upper rib members (124) connected between the leading edge tubular member (114) and the upper tubular member (110); one or more lower rib members (126) connected between the leading edge tubular member (114) and the lower tubular member (112); a rigid sandwich shell (102) disposed between the upper tubular member (110) and the leading edge tubular member (114); a sandwich shear web (104) disposed between the upper tubular member (110) and the lower tubular member (112); The system, wherein the rigid sandwich shell (102) and the sandwich shear web (104) form a D-shape.

2. 10. The system of claim 1, The system of claim 1, wherein said leading edge tubular member (114), said upper tubular member (110) and said lower tubular member (112) support all bending loads.

3. 10. The system of claim 1, The system, wherein the rigid sandwich shell (102) includes one or more expansion joints (122A, 122B).

4. 4. The system of claim 3, A system comprising: each expansion joint (122A, 122B) extending between the leading edge tubular member (114) and the upper tubular member (110).

5. 5. The system of claim 4, The system further comprises a polyvinyl fluoride (PVF) film covering the system except for the rigid sandwich shell (102), the PVF film providing an airfoil shape.

6. 6. The system of claim 5, The system, wherein the PVF film covers one or more channels formed by the one or more expansion joints.

7. 10. The system of claim 1, The system wherein the rigid sandwich shell (102) comprises two thin composite face sheets separated by a low density core.

8. 8. The system of claim 7, The system wherein the two thin composite face sheets comprise carbon fiber and epoxy.

9. 8. The system of claim 7, The system, wherein the low density core comprises foam.

10. 8. The system of claim 7, The system wherein the low density core comprises a honeycomb.

11. 10. The system of claim 1, The system further comprises one or more cross brace members (108) connected between each of the one or more lower rib members (126).

12. 12. The system of claim 11, 10. The system of claim 9, wherein each of the one or more cross brace members (108) is configured to pull the lower tubular member (112) toward the leading edge tubular member (114).

13. a leading edge tubular member (114); an upper tubular member (110); one or more upper rib members (124) connected between the leading edge tubular member (114) and the upper tubular member (110); a rigid sandwich shell (102) disposed between the upper tubular member (110) and the leading edge tubular member (114).

14. 14. The system of claim 13, The system further comprises a lower tubular member (112).

15. 15. The system of claim 14, The system further comprises one or more lower rib members (126) coupled between the leading edge tubular member (114) and the lower tubular member (112).

16. 16. The system of claim 15, The system further comprises a sandwich shear web (104) disposed between the upper tubular member (110) and the lower tubular member (112).

17. 17. The system of claim 16, The system, wherein the rigid sandwich shell (102) and the sandwich shear web (104) form a D-shape.

18. 18. The system of claim 17, The system of claim 1, wherein said leading edge tubular member (114), said upper tubular member (110) and said lower tubular member (112) support all bending loads.

19. 18. The system of claim 17, The system, wherein the rigid sandwich shell (102) includes one or more expansion joints (122A, 122B).

20. 20. The system of claim 19, A system comprising: each expansion joint (122A, 122B) extending between the leading edge tubular member (114) and the upper tubular member (110).

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