Patent ID: 12214875

DETAILED DESCRIPTION

With respect toFIG.1, a D-truss wing structure100for wing panels of an unmanned aerial vehicle (UAV) is depicted. A thickness101of the elements of the D-truss wing structure100is shown for reference. While the D-truss wing structure100is depicted and described for a UAV, it may also be used with other aerial vehicles in some embodiments. UAVs are aircraft with no onboard pilot and may fly autonomously or remotely. In one embodiment, the UAV is a high altitude long endurance aircraft. In one embodiment, the UAV may have one or more motors, for example, between one and forty (40) motors, and a wingspan between one hundred (100) feet and four hundred (400) feet. In one embodiment, the UAV has a wingspan of approximately two hundred sixty (260) feet and is propelled by a plurality of propellers coupled to a plurality of motors, for example, ten (10) electric motors, powered by a solar array covering the surface of the wing, resulting in zero emissions. Flying at an altitude of approximately sixty five thousand (65,000) feet above sea level and above the clouds, the UAV is designed for continuous, extended missions of up to months without landing.

The UAV functions optimally at high altitude and is capable of considerable periods of sustained flight without recourse to land. In one embodiment, the UAV may weigh approximately three thousand (3,000) lbs.

The D-truss wing structure100may include a rigid sandwich shell102that wraps around a leading edge106, a sandwich shear web104, an upper tubular truss rib member (124,FIG.3), a lower tubular truss member (126,FIG.3), and one or more lightweight cross-bracing members108. The wing structure100may further include an upper tubular member110, a lower tubular member112, and a leading-edge tubular member114that serve as spar caps and take all bending loads. The three spanwise running tubes are the “caps”. The tubular caps134A,134B,134C may include a first tubular cap134A, a second tubular cap134B, and a third tubular cap134C. In one embodiment, the tubular members110,112,114have a small diameter relative to a thickness of the wing airfoil and/or the height of the shear web104. In one embodiment, the diameter of the tubular members and wall thicknesses may be optimized for resistance to buckling under all bending loads at minimum weight. In one embodiment, the diameter of the tubular members may be on the order of one tenth of the height of the sandwich shear web104. In one embodiment, the sandwich shear web104may include a main shear web136with a ¼-inch thick core. In one embodiment, the upper tubular member110may have an approximate material thickness of 0.337-0.360 inches. In one embodiment, the lower tubular member112may have an approximate material thickness of 0.266 inches-0.291 inches. In one embodiment, the forward tubular member114may have an approximate material thickness of 0.177 inches-0.199 inches. The tubular members110,112,114may carry all bending loads and are continuous over the length of a separable wing panel, where some number of wing panels (e.g., seven wing panels) are connected end-to-end to form the full wing. More specifically, the upper tubular member110, lower tubular member112, and leading tubular member114may be arranged at the three extreme points of the “D”-shape formed by the leading edge106and the sandwich shear web104to carry all bending loads. In some embodiments, the leading edge106may include a leading edge shell138with a 3/16-inch thick core. The shear web104is essentially perpendicular to a wing chord plane, which runs from the wing leading edge to the wing trailing edge. The chord plane is angled with respect to the ground by the angle of attack of the wing in level flight. A typical angle of attack for an aerial vehicle with the disclosed D-truss wing structure100may be 10-12 degrees, leading edge high. Shear between the tubular members110,112,114may be carried by the sandwich shear web104between the upper tubular member110and lower tubular member112, the rigid sandwich shell102between the upper tubular member110and the leading tubular member114, and the light weight cross-bracing108between the lower tubular member112and the leading tubular member114. In one embodiment, the rigid sandwich shell102may have an approximate material thickness of 0.177 inches-0.199 inches and the shear sandwich web104may have an approximate material thickness of 0.245 inches-0.266 inches. In some embodiments, the disclosed ranges may be wider to accommodate aerial vehicles having between 1 to 40 motors and/or 100 to 400 feet of span.

With respect toFIG.2, the rigid sandwich shell102is illustrated. In one embodiment, the rigid sandwich shell102carries sheet. In one embodiment, the rigid sandwich shell102may have a plurality of expansion joints122A,122B. Each expansion joint122A,122B may run from the leading edge of the sandwich edge shell114to the rear of the rigid sandwich shell102at the upper tubular member110. In one embodiment, the expansion joints122A,122B allow the rigid sandwich shell102to handle the “spanwise” expansion and contraction associated with bending, and also allow for the rigid sandwich shell102to carry in-plane and torsional shear. In some embodiments, the expansion joints122A,122B provide for spanwise expansion, but still carry shear. Additionally, the rigid sandwich shell102may provide for stabilizing the upper tubular member110and the leading tubular member114. The rigid sandwich shell102may also maintain the airfoil shape. In one embodiment, all elements ofFIG.1may be made of composite materials, such as carbon fiber and epoxy. In some embodiments, the sandwich shell102may be made from non-conductive materials, such as Kevlar (aramid) or fiberglass so as to avoid electrical shorting of the solar array. The rigid sandwich shell102and the sandwich shear web104may be made of two thin composite face sheets separated by a low-density core. The composite may be made of carbon fiber and epoxy. In other embodiments, the composite may be made of Kevlar or fiberglass. The low-density core may be made of either foam or honeycomb. The combination provides high bending stiffness at minimal weight. In one embodiment, a polyvinyl fluoride (PVF) film, such as Tedlar film covers the wing structure100(except for the rigid sandwich shell102) and provides the airfoil shape. In other embodiments, a non-structural material may be used to cover the wing structure100(except for the rigid sandwich shell102) to provide the airfoil shape. In one embodiment, the Tedlar film may also be used to cover channels formed by the expansion joints122A,122B. In other embodiments, a tape having stretch characteristics may be used to cover channels formed by the expansion joints122A,122B.

In one embodiment, the rigid sandwich shell102may have a molded surface that is substantially hard and smooth to allow solar modules to be bonded directly thereto. In one embodiment, the face sheet material of the rigid sandwich shell102may be made of Kevlar and epoxy in order to be non-conductive.

With respect toFIG.3, the rigid sandwich shell102has been removed to reveal the upper tubular member110, the lower tubular member112, and the leading tubular member114being held in position relative to each other. More specifically, a plurality of upper rib members124are connected to the upper tuber member110and leading tubular member114. In one embodiment, the upper rib members124connect to and hold the upper tubular member100and leading tubular member114in position relative to each other. Additionally, a plurality of lower rib members126are connected to the lower tubular member112and leading tubular member114.

With respect toFIG.4, the upper rib members124support the rigid sandwich shell (102,FIG.2) through small webs130connected to the expansion joints. The lower rib member (126,FIG.3) react the cross-bracing tensile loads. More specifically, the cross-bracing members (108,FIG.3) only carry tensile loads, since the cross-bracing members (108,FIG.3) may buckle under compressive loads. Therefore, the cross-bracing members (108,FIG.3) act to pull the lower tubular members (112,FIG.3) and the forward tubular members (114,FIG.3) toward each other. The lower rib members (126,FIG.3), which are loaded in compression in this case, keep the lower tubular members (112,FIG.3) and the forward tubular members (114,FIG.3) separated. In one embodiment, each expansion joint122A creates an expansion channel402. In one embodiment, the upper rib member124is a tuber truss member.

With respect toFIGS.2-3, in one embodiment, the interconnection of an upper rib member124, a lower rib member126, the tubular members110,112,114, the rigid sandwich shell102that wraps around the leading edge106, and the sandwich shear web104generally forms a D-shape. The ‘D’ shape may not include a shell between the leading edge tubular member114and the lower tubular member112. Therefore, each D-truss wing structure100may have series of so-called “D-truss” structures128. In one embodiment, the upper rib members124and the lower rib members126may have an approximate material thickness of 0.038 inches-0.062 inches. In one embodiment, the upper rib members124, the lower rib members126, and the tubular members110,112,114may be made of carbon fiber.

For additional clarity, a cut-away, cross-section view of the upper tubular truss rib member124ofFIG.4is shown inFIG.5. One or more expansion joints122A are provided in the rigid sandwich shell102proximate the upper tubular truss rib member124. Small webs130connect the rib member124to the one or more expansion joints122A.

Returning toFIG.3the lightweight cross-bracing members108are also shown. In one embodiment, the lightweight cross-bracing members108complete the torsion load path across the bottom of the D-truss wing panel structure (100,FIG.2). In one embodiment, the lightweight cross-bracing members108may be installed without provisions for adjusting tension, effectively giving the lightweight cross-bracing members108zero preload. In one embodiment, the lower rib members126may support batteries for operating the UAV and the battery support structures132might take the place of the lightweight cross-bracing members108. In one embodiment, the battery support structure132may be a plate or a box that occupies the area that would otherwise be occupied by a cross-bracing member108pair in rib bays (e.g., spaces between adjacent ribs) that have batteries. The battery plate or box132may be strong enough to take the loads normally taken by the cross-bracing members108. Batteries will only occupy a small fraction of the total number of rib bays (e.g., 22 out of 148 rib bays in one embodiment) and the remaining rib bays may still have cross-bracing members108. In one embodiment, the D-truss wing panel structure (100,FIG.2) may include one or more tubular truss members140,142. In one embodiment, the D-truss wing panel structure (100,FIG.2) may include X-Bracing144for torsion.

FIG.6depicts a side view of a wing600including the D-truss wing structure100of the unmanned aerial vehicle. The wing600may include the sandwich shell102between the leading edge tubular member114and the upper tubular member110; the sandwich shear web104disposed between the upper tubular member110and the lower tubular member112; a first plastic membrane skin602on a top surface of the wing600; and a second plastic membrane skin604on a bottom surface of the wing600. In one embodiment, a polyvinyl fluoride (PVF) film, such as Tedlar film covers the wing600(except for the rigid sandwich shell102) and provides the airfoil shape. In other embodiments, a non-structural material may be used to cover the wing600(except for the rigid sandwich shell102) to provide the airfoil shape.

It is contemplated that various combinations and/or sub-combinations of the specific features and aspects of the above embodiments may be made and still fall within the scope of the invention. Accordingly, it should be understood that various features and aspects of the disclosed embodiments may be combined with or substituted for one another in order to form varying modes of the disclosed invention. Further, it is intended that the scope of the present invention is herein disclosed by way of examples and should not be limited by the particular disclosed embodiments described above.