Patent Publication Number: US-2023159153-A1

Title: System of morphing control surface for aircraft wing

Description:
TECHNICAL FIELD 
     The disclosure herein relates to a morphing aircraft control surface. 
     BACKGROUND 
     Generally, an aircraft control surface, such as an aileron, is set in motion about an articulation axis using an actuator. This articulation axis corresponds also to an axis of attachment of the control surface to a wing of the aircraft. The control surface is rigid. The moving of such a control surface to a deflection angle associated with a desired lift coefficient entails a fairly great expenditure of energy from the actuator. 
     SUMMARY 
     An object of the disclosure herein is to remedy this drawback. For that, it relates to a morphing control surface system for an aircraft wing, the wing comprising an upper plane and a lower plane. 
     According to the disclosure herein, the control surface system comprises at least:
         an upper flexible skin intended to be fixed to the wing in the extension of the upper plane of the wing;   a lower flexible skin intended to be movable in the extension of the lower plane of the wing via a plane-to-plane link, the lower flexible skin being fixed to the upper flexible skin along a trailing edge of the control surface;   at least one actuator intended to generate a displacement of the lower flexible skin with respect to the lower plane of the wing,       

     the displacement of the lower flexible skin causing a curvature of the upper flexible skin and a curvature of the lower flexible skin, the curvature of the upper flexible skin and the curvature of the lower flexible skin having a concavity oriented in a same direction. 
     Thus, by virtue of the deformation of the flexible skins by a curvature, the necessary deflection angle of the control surface system is less great than the necessary deflection angle of a rigid control surface system for a same lift coefficient. Thus, the quantity of energy to be supplied by the actuator is much less great than the quantity of energy to be supplied by the actuator of a rigid control surface system for a same lift coefficient. 
     Furthermore, the actuator or actuators comprise at least one actuator axis arranged to be displaced longitudinally between the upper flexible skin and the lower flexible skin, the actuator axis or axes comprising an end fixed to an inner surface of the lower flexible skin. 
     Furthermore, the actuator or actuators are fixed onto an inner surface of the lower plane of the wing. 
     According to a particular feature, the actuator axis or axes are configured to each slide through an aperture of a rear spar of the wing. 
     For example, the control surface system comprises at least one linear ball-type guide bushing configured to be mounted on the aperture or apertures through which the actuator axis or axes can slide. 
     Moreover, the control surface system further comprises at least one auxiliary axis parallel to the actuator axis or axes, the auxiliary axis or axes having a first end fixed to the rear spar and a free second end directed toward the trailing edge of the control surface system, the control surface system further comprising at least one auxiliary bushing fixed onto the inner surface of the lower flexible skin, the free second end being able to slide in the auxiliary bushing. 
     According to a particular feature, the control surface system further comprises an internal skeleton between the upper flexible skin and the lower flexible skin, the internal skeleton having a compressive and tensile strength on an axis substantially at right angles to the upper flexible skin or the lower flexible skin greater than a shear strength of the internal skeleton on an axis substantially parallel to the upper flexible skin or the second, lower flexible skin. 
     The disclosure herein relates also to an aircraft, in particular a transport airplane, comprising at least one control surface system, as described above, equipping each of its wings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The attached figures will give a good understanding of how the disclosure herein can be produced. In these figures, references that are identical denote similar elements. 
         FIG.  1    represents a cross-sectional view of a control surface system according to two different positions. 
         FIG.  2    represents a cross-sectional schematic view of a control surface system according to two different positions. 
         FIG.  3    represents a perspective view of an aircraft wing equipped with the morphing control surface system. 
         FIG.  4    represents a worm&#39;s-eye view of a cross section of a control surface system. 
         FIG.  5    represents a bird&#39;s-eye view of a cross section of a control surface system. 
         FIG.  6    represents, on the right, a view of a cross section along an actuator axis of a control surface system and, on the left, a detail of the cross section. 
         FIG.  7    represents, on the right, a view of a cross section along an auxiliary axis of a control surface system and, on the left, a detail of the cross section. 
         FIG.  8    represents a cross section of the two flexible skins highlighting the transverse change in their thickness. 
         FIG.  9    represents a perspective view of an embodiment of the control surface system comprising an internal skeleton. 
         FIG.  10    represents a perspective view of an aircraft whose wings are equipped with control surface systems. 
     
    
    
     DETAILED DESCRIPTION 
       FIG.  1    represents the morphing control surface system  1  for a wing  2  of an aircraft AC ( FIG.  10   ). The morphing control surface system  1  can correspond to a morphing aileron system. 
     A morphing control surface corresponds to a non-rigid control surface which can be deformed to change geometrical shape. 
     The wing  2 , that the control surface system  2  is intended to equip, comprises an upper plane  3  and a lower plane  4 . 
     The control surface system  1  comprises at least an upper flexible skin  5  and a lower flexible skin  6 . The upper flexible skin  5  and the lower flexible skin  6  meet to form a trailing edge  7  of the control surface system  1 . In a non-limiting manner, the flexible skins  5  and  6  can be manufactured in thermoplastic composite or in thermosetting composite. 
     The upper flexible skin  5  is intended to be fixed to the wing  2  in the extension of the upper plane  3  of the wing  2 . As a nonlimiting example, the upper flexible skin  5  can be fixed to the upper plane  3  of the wing  2  using countersunk head screws. 
     The lower flexible skin  6  is intended to be movable in the extension of the lower plane  4  of the wing  2  via a plane-to-plane link between the lower plane  4  and the lower flexible skin  6 . The lower flexible skin  6  is fixed to the upper flexible skin  5  along the trailing edge  7 . 
     As a nonlimiting example, the lower flexible skin  6  is fixed to the upper flexible skin  5  along the trailing edge  7  by welding in the case where the upper  5  and lower  6  flexible skins are manufactured from thermoplastic composite. They can also be fixed together along the trailing edge  7  by cofiring in the case where they are manufactured from thermoplastic or thermosetting composite. They can also be fixed together along the trailing edge  7  by bonding or by rivets. 
     Advantageously, as represented in  FIG.  8   , the upper flexible skin  5  has a greater thickness in a zone Z 51  situated at the trailing edge  7  and in a zone Z 52  situated at the fixing of the upper flexible skin  5  to the upper plane  3  of the wing  2  than in a central zone Z 53  situated between the zone Z 51  and the zone Z 52 . Likewise, the lower flexible skin  6  has a greater thickness in a zone Z 61  situated at the trailing edge  7  and in a zone Z 62  situated at the plane-to-plane link between the lower flexible skin  6  and the lower plane  4  of the wing  2  than in a central zone Z 63  situated between the zone Z 61  and the zone Z 62 . 
     The dotted lines in  FIG.  8    designate the approximate limits of the different zones. 
     In a nonlimiting manner, the thickness ratio between the zone Z 51  and the central zone Z 53  is between 2 and 3. The thickness ratio between the zone Z 52  and the central zone Z 53  is between 4 and 5. As an example, the zone Z 51  has a thickness of between 2.20 mm and 1.95 mm. The zone Z 52  has a thickness of between 2.5 mm and 3 mm. The zone Z 53  has a thickness of between 0.715 mm and 0.975 mm. 
     Likewise and in a nonlimiting manner, the thickness ratio between the zone Z 61  and the central zone Z 63  is between 2 and 3. The thickness ratio between the zone Z 62  and the central zone Z 63  is between 4 and 5. As an example, the zone Z 61  has a thickness of between 2.20 mm and 1.95 mm. The zone Z 62  has a thickness of between 2.5 mm and 3 mm. The zone Z 63  has a thickness of between 0.715 mm and 0.975 mm. 
     These thickness ratios make it possible to control the form of curvature of the flexible skins  5  and  6 . 
     According to one embodiment, the thickness between the zones Z 51 , Z 52 , Z 53 , Z 61 , Z 62 , Z 63  can change continuously. According to another embodiment, the thickness between the zones Z 51 , Z 52 , Z 53 , Z 61 , Z 62 , Z 63  can change in staircase fashion as represented in  FIG.  8   . 
     As represented in  FIG.  3   , the control surface system  1  further comprises at least one actuator  8  intended to generate a displacement D of the flexible skin  6  with respect to the lower plane  4  of the wing  2 . In  FIG.  1   ,  FIG.  6    and  FIG.  7   , the displacement D generated by the actuator or actuators  8  is represented by a double-headed arrow. 
     The actuator or actuators  8  are configured to generate a linear displacement of the lower flexible skin  6  in two opposite directions. The direction of displacement D of the lower flexible skin  6  can be directed alternately toward the trailing edge  7  or directed away from the trailing edge  7 . 
     The displacement D of the lower flexible skin  6  causes a curvature of the upper flexible skin  5  and a curvature of the lower flexible skin  6 . The curvature of the upper flexible skin  5  and the curvature of the lower flexible skin  6  have a concavity C 1 , C 2  oriented in a same direction, as represented in  FIG.  1    and  FIG.  2   . In  FIG.  1   , a position P 1  and a second position P 1   a  are represented. In  FIG.  2   , a position P 1   b  in which the flexible skins  5  and  6  have a substantially nil curvature and a position P 1  in which the flexible skins  5  and  6  have a non-nil curvature are represented. The direction of the concavity C 1 , C 2  generated by a displacement D directed toward the trailing edge  7  is opposite to the direction of the concavity C 1 , C 2  generated by a displacement D directed away from the trailing edge  7 . 
     The actuator or actuators  8  comprise at least one actuator axis  9  arranged to be displaced longitudinally between the upper flexible skin  5  and the lower flexible skin  6 . The actuator axis or axes  9  comprise an end  10  fixed to an inner surface  61  of the lower flexible skin  6 . As represented in  FIG.  4   ,  FIG.  5    and  FIG.  6   , the end  10  can be fixed to the inner surface  61  of the lower flexible skin  6  via an axis support. The axis support can comprise a surface  19  fixed to the inner surface  61  of the lower flexible skin  6  and a flange  20  in which the end  10  is blocked or fixed ( FIG.  1   ,  FIG.  4    and  FIG.  6   ). The inner surface  61  of the lower flexible skin  6  corresponds to a surface of the lower flexible skin  6  directed toward the upper flexible skin  5 . 
     Advantageously, as represented in  FIG.  6   , the actuator or actuators  8  are fixed onto an inner surface  41  of the lower plane  4  of the wing  2 . Thus, the actuator axis or axes  9  are displaced linearly with respect to the wing  2 . The inner surface  41  of the lower plane  4  of the wing  2  corresponds to a surface of the lower plane  4  directed toward the upper plane  3  of the wing  2 . Moreover, the actuator axis or axes  9  contribute to maintaining the plane-to-plane link between the lower flexible skin  6  and the lower plane  4 . 
     Thus, when the actuator or actuators  8  are actuated, the actuator axis or axes  9  are displaced linearly on their respective longitudinal axes. Since the end  10  of the actuator axis or axes  9  is fixed to the lower flexible skin  6 , the lower flexible skin  6  is driven by the actuator axis or axes  9 . Since the lower flexible skin  6  is fixed to the upper flexible skin  5  along the trailing edge  7 , the lower flexible skin  6  and the upper flexible skin  5  are deformed to form the curvature described above. 
     Between the upper plane  3  and the lower plane  4  of the wing  2 , the wing  2  can comprise a rear spar  12  extending over the entire span of the wing  2 . This rear spar  12  is situated as close as possible to the trailing edge of the wing  2 . 
     The actuator axis or axes  9  can be configured to each slide through an aperture  11  of the rear spar  12  of the wing  2 . The rear spar  12  can then serve as a guide for the actuator axis or axes  9 . 
     The control surface system  1  can also comprise at least one linear ball-type guide bushing  13  configured to be mounted on the aperture or apertures  11  of the rear spar  12  through which the actuator axis or axes  9  can slide. 
     Advantageously, as represented in  FIG.  7   , the control surface system  1  can further comprise at least one auxiliary axis  15 . The auxiliary axis or axes  15  are parallel to the actuator axis or axes  9 . The auxiliary axis or axes  15  have an end  16  fixed to the rear spar  12  and a free end  18  directed toward the trailing edge  7  of the control surface system  1 . The control surface system  1  further comprises at least one auxiliary bushing  17  fixed onto the inner surface  61  of the lower flexible skin  6 . The free end  18  can slide in the auxiliary bushing  17 . The auxiliary bushing or bushings  17  serve as guide for the auxiliary axis or axes  15 . The auxiliary bushing or bushings can be fixed to the inner surface  61  using an axis support. The axis support can comprise a surface  21  fixed onto the inner surface  61  of the lower flexible skin  6  and a flange  22  on which the auxiliary bushing is mounted ( FIG.  7   ). Thus, when the actuator or actuators  8  are actuated, the actuator axis or axes  9  drive the lower flexible skin  6 . The driving of the lower flexible skin  6  makes it possible to generate a displacement of the lower flexible skin  6 . The displacement of the lower flexible skin  6  drives the auxiliary bushing or bushings  17  which are then displaced about the auxiliary axis or axes  15 . Moreover, the auxiliary axis or axes  15  contribute to maintaining the plane-to-plane link between the lower flexible skin  6  and the lower plane  4 . 
     The actuator or actuators  8  and the auxiliary axes  15  have dimensions allowing them to be incorporated in a wing  2 . 
     Furthermore, the morphing control surface system  1  makes it possible to reduce the necessary travel of the actuator axis  9  and the necessary load supplied by the actuator or actuators  8  with respect to the necessary travel and the necessary load of a rigid control surface system for a same lift coefficient. 
     As represented in  FIG.  9   , the control surface system can further comprise an internal skeleton  14  between the upper flexible skin  5  and the lower flexible skin  6 . The internal skeleton  14  has a compressive and tensile strength on an axis substantially at right angles to the upper flexible skin  5  or the lower flexible skin  6  greater than a shear strength of the internal skeleton  14  on an axis substantially parallel to the upper flexible skin  5  or the lower flexible skin  6 . 
     While at least one example embodiment of the invention(s) is disclosed herein, it should be understood that modifications, substitutions and alternatives may be apparent to one of ordinary skill in the art and can be made without departing from the scope of this disclosure. This disclosure is intended to cover any adaptations or variations of the example embodiment(s). In addition, in this disclosure, the terms “comprise” or “comprising” do not exclude other elements or steps, the terms “a”, “an” or “one” do not exclude a plural number, and the term “or” means either or both. Furthermore, characteristics or steps which have been described may also be used in combination with other characteristics or steps and in any order unless the disclosure or context suggests otherwise. This disclosure hereby incorporates by reference the complete disclosure of any patent or application from which it claims benefit or priority.