System and method for deflecting an aerodynamic control surface

[0002] This invention relates generally to the field of aerostructures and, more specifically, to a system and method for deflecting an aerodynamic control surface.

[0003] Control surfaces, such as flaps, ailerons, and elevators, control the direction of, and provide stability for, aeronautic vehicles, such as aircrafts. Control surfaces accomplish this control by being driven by various actuation systems. Manufacturers of control surfaces and their corresponding actuation systems desire simple designs for safety reasons and for saving space inside a wing. In addition, control surface manufacturers design and construct control surfaces to handle high aerodynamic loads and to respond quickly to pilot inputs. Some aerodynamic applications require that control surfaces accomplish large deflections quickly and smoothly to increase aerodynamic efficiency.

[0004] Some previous actuation systems, such as hydraulic, pneumatic, electro-mechanical, and electro-hydraulic systems, require many components to construct a single actuator. In addition, some of these previous systems require a high-force actuator with a long stroke. The complexity and operation of these previous systems prevent the usage of multiple actuation systems for added redundancy and improved safety. Additionally, the complexity of these previous systems wastes considerable space that can reduce fuel storage area. Additional problems with these previous systems, among others, is that they have relatively slow response times and are unable to facilitate the use of multiple control surfaces in a smooth, economical, and efficient manner.

[0005] The challenges in the field of aerostructures continue to increase with demands for more and better techniques having greater flexibility and adaptability. Therefore, a need has arisen for a new system and method for deflecting an aerodynamic control surface.

[0006] In accordance with the present invention, a system and method for deflecting an aerodynamic control surface is provided that addresses disadvantages and problems associated with previously developed systems and methods.

[0007] According to one embodiment of the invention, a system for deflecting an aerodynamic control surface includes a first piezoelectric actuator coupled to a first flexure member. The first flexure member has a first end coupled to a first surface of the aerodynamic control surface and is operable to amplify a linear motion of the first piezoelectric actuator. The system further includes a second piezoelectric actuator coupled to a second flexure member. The second flexure member has a first end coupled to a second surface of the aerodynamic control surface and is operable to amplify a linear motion of the second piezoelectric actuator.

[0008] According to another embodiment of the invention, a method for deflecting an aerodynamic control surface includes rotatably coupling a first end of a first flexure member to a first surface of the aerodynamic control surface, rotatably coupling a first end of a second flexure member to a second surface of the aerodynamic control surface, rotatably coupling a first piezoelectric actuator to the first flexure member, rotatably coupling a second piezoelectric actuator to the second flexure member, electrically coupling an electronic power source to the first and second piezoelectric actuators, and inputting a first electrical charge into the first piezoelectric actuator and a second electrical charge into the second piezoelectric actuator. The first and second flexure members, in conjunction with one another, translate a first linear motion of the first piezoelectric actuator and a second linear motion of the second piezoelectric actuator into a rotational motion of the aerodynamic control surface.

[0009] Embodiments of the invention provide numerous technical advantages. For example, a technical advantage of one embodiment of the present invention is that a small piezoelectric actuator stroke produced at a high rate and force allows useful control surface deflections. Another technical advantage of one embodiment of the present invention is that the simplicity of a piezoelectric actuation system allows multiple control surface usage for enhanced safety and larger control surface deflections. In addition, the use of multiple control surfaces results in smooth control surface deflections that have maximum aerodynamic efficiency.

[0010] Other technical advantages are readily apparent to one skilled in the art from the following figures, descriptions, and claims.

[0011] For a more complete understanding of the invention, and for farther features and advantages, reference is now made to the following description, taken in conjunction with the accompanying drawings, in which:

[0012] FIG. 1A is a perspective view of an aircraft having multiple aerodynamic control surfaces according to one embodiment of the present invention;

[0013] FIG. 1B is a perspective view illustrating a portion of a wing of the aircraft in FIG. 1A employing a plurality of piezoelectric actuation systems for deflecting multiple aerodynamic control surfaces according to one embodiment of the present invention;

[0014] FIG. 2A is an elevation view of the portion of the aircraft wing in FIG. 1 illustrating the aircraft wing in an undeflected position and showing details of a piezoelectric actuation system of FIG. 1 with greater clarity;

[0015] FIG. 2B is an elevation view of the portion of the aircraft wing in FIG. 1 illustrating the aircraft wing in a deflected position; and

[0016] FIG. 3 is a flowchart illustrating one method for deflecting an aerodynamic control surface according to one embodiment of the present invention.

[0017] Example embodiments of the present invention and their advantages are best understood by referring now to FIGS. 1A through 3 of the drawings, in which like numerals refer to like parts.

[0018] FIG. 1A is a perspective view of an aircraft 90 having multiple aerodynamic control surfaces 104 according to one embodiment of the present invention. Control surfaces 104, such as flaps, ailerons, rudders, and elevators, control the direction of, and provide stability for, aeronautic vehicles, such as aircraft 90. Control surfaces 104 accomplish this control by being driven by actuation systems, such as the system shown in FIG. 1B.

[0019] FIG. 1B is a perspective view illustrating a portion of an aircraft wing 100 of aircraft 90 employing a plurality of piezoelectric actuation systems 102 for deflecting respective aerodynamic control surfaces 104 according to one embodiment of the present invention. Aircraft wing 100, which in other embodiments may be a tail fin 94 or tail plane 96 of aircraft 90, includes one or more control surfaces 104 and one or more main segments 106. Aircraft wing 100 may also include one or more flexible material skins 105, one or more spars 108, and various ribs and stiffeners (not explicitly shown).

[0020] In one embodiment, control surfaces 104 are flaps; however, control surfaces 104 may be other suitable types of control surfaces, such as ailerons, rudders, and elevators. Control surfaces 104 function to control the direction and stability of aircrafts, such as aircraft 90. In this embodiment, control surfaces 104 couple to main segment 106, which may attach to, or be integral with, a body 92 of aircraft 90.

[0021] Flexible material skins 105 allow control surfaces 104 to deflect in a smooth and rapid manner so that an aircraft remains stable and vibration-free during flight. Flexible material skins 105 are typically made of a flexible material, such as rubber, polymer, or composite material. Flexible material skins 105 are mechanically attached to control surfaces 104 and/or main segments 106 of aircraft wing 100.

[0022] Spars 108, which typically run a length 114 of aircraft wing 100, provide strength to aircraft wing 100. Since spars 108 are normally main members of aircraft wing 100, they are made of a suitable material, such as aluminum. However, spars 108 may be made of other high-strength, low-weight materials, such as other metals or composite materials.

[0023] According to the teachings of the present invention, one or more piezoelectric actuation systems 102 are used to control the deflection of control surfaces 104. Piezoelectric actuation system 102, which is described in greater below in conjunction with FIGS. 2A and 2B, includes a pair of piezoelectric actuators 110a, 110band a corresponding pair of flexure members 112a, 112b. Piezoelectric actuators 110a, 110band flexure members 112a, 112bwork in conjunction with one another to translate a linear motion of piezoelectric actuators 110a, 110binto a rotational motion of control surfaces 104, as described in greater detail below.

[0024] One or any number of piezoelectric actuation systems 102 are employed depending on the size of aircraft wing 100 and the number of control surfaces 104 existing on aircraft wing 100. For example, as shown in FIG. 1, two control surfaces 104 exist on aircraft wing 100. Therefore, there are at least two piezoelectric actuation systems 102 present—one for each control surface 104. In the embodiment shown in FIG. 1, four sets of piezoelectric actuation systems 102 are present because length 114 of aircraft wing 100 utilizes multiple piezoelectric actuation systems 102 for each control surface 104 for structural and stability purposes. The distance between each piezoelectric actuation system 102 for each control surface 104 varies depending on the design parameters for a particular aircraft wing 100. In one particular embodiment, piezoelectric actuation systems 102 are spaced at a distance of approximately twenty inches; however, other suitable distances may be used. For more details of piezoelectric actuation system 102 reference is now made to FIGS. 2A and 2B.

[0025] FIGS. 2A and 2B are elevation views of a portion of aircraft wing 100 shown in FIG. 1, illustrating aircraft wing 100. in undeflected and deflected positions, respectively, and showing additional details of piezoelectric actuation system 102. FIGS. 2A and 2B are two-dimensional views illustrating one embodiment of the present invention. FIG. 2A shows two piezoelectric actuation systems 102 utilized with two control surfaces 104.

[0026] Piezoelectric actuation system 102 includes first piezoelectric actuator 110a, second piezoelectric actuator 110b, first flexure member 112a, and second flexure member 112b. Piezoelectric actuation system 102 further includes an electronic power source 200 and an electronic power drive 202. As shown in FIG. 2A, first piezoelectric actuator 110ais coupled to a first surface 204 of main segment 106 at one end and coupled to first flexure member 112aat another end. Similarly, second piezoelectric actuator 110bis coupled to a second surface 206 of main segment 106 at one end and coupled to second flexure member 112bat another end. First flexure member 112ais coupled adjacent first surface 204 of main segment 106 at one end and coupled to a second surface 205 of control surface 104 at another end. Similarly, second flexure member 112bis coupled adjacent second surface 206 of main segment 106 at one end and coupled to a first surface 207 of control surface 104 at another end. Second flexure member 112bis adjacent first flexure member 112aas seen most clearly in the perspective view of FIG. 1. In one embodiment, first flexure member 112aand second flexure member 112bare spaced at a distance of approximately three inches; however, first flexure member 112aand second flexure member 112bmay be spaced at any suitable distance.

[0027] In one embodiment, first flexure member 112aand second flexure member 112btake the form of a cross-linkage as illustrated in FIG. 2A; however, other configurations may be used that are suitable for translating a linear motion of piezoelectric actuators 110a, 110binto a rotational motion of control surfaces 104. As described below in conjunction with FIG. 2B, any suitable configuration for translating and amplifying a linear displacement of piezoelectric actuators 110a, 110binto a more substantial rotational motion of control surfaces 104 may be used. In other words, flexure members 112a, 112bact as levers to amplify the relatively short stroke of piezoelectric actuators 110a, 110b.

[0028] Piezoelectric actuators are translation elements that linearly expand or contract in response to an electrical charge, such as a voltage. They are sometimes referred to as “smart materials.” In one embodiment, piezoelectric actuators 110a, 110bare P-845 stacked-type piezoelectric translators manufactured by Polytec PI, Inc.; however, other suitable types of piezoelectric actuators may be used. Piezoelectric actuators 110a, 110bprovide good linearity, stability, and accuracy. In addition, piezoelectric actuators 110a, 110bprovide very fast response time, high stiffness, zero backlash, very little wear and tear, and typically come in small configurations, which saves space inside aircraft wing 100. The small configuration of piezoelectric actuators 110a, 110bresult in one technical advantage of the present invention, in that more space can be utilized for items such as fuel.

[0029] As described above, an end of piezoelectric actuators 110a, 110bis coupled to surfaces 204, 206 of main segment 106. This may be accomplished in any suitable manner, such as in a rotatable manner, as long as the coupling arrangement can handle the loads that are expected to be encountered during flight of aircraft 90. Similarly, the other ends of piezoelectric actuators 110a, 110bare coupled to flexure members 112a, 112bin any suitable manner. In one embodiment, flexure members 112a, 112brotate about a hinged connection in response to a linear expansion or contraction of piezoelectric actuators 110a, 110b. In addition, these ends of piezoelectric actuators 110a, 110bmay be coupled to flexure members 112a, 112bin any suitable location.

[0030] As mentioned previously, piezoelectric actuators 110a, 110blinearly expand or contract based on an applied electrical charge, such as a voltage. The expansion or contraction enables a somewhat small actuator stroke. For example, a stroke of approximately a tenth of an inch may result from applied voltages to piezoelectric actuators 110a, 110b. This means that to produce useful surface deflection of control surfaces 104, an amplification system may need to be utilized. Flexure members 112a, 112bmay accomplish this amplification as described below in conjunction with FIG. 2B.

[0031] Flexure members 112a, 112b, in one embodiment, are structural members having a rectangular cross-section formed from a metal, such as aluminum; however, flexure members 112a, 112bmay be formed in other configurations and may be formed from other suitable types of materials, such as other metals, composites, or plastics. As mentioned previously, one end of flexure members 112a, 112bare coupled adjacent surface 204, 206 of main segment 106. This coupling may be accomplished in any suitable manner. For example, flexure members 112a, 112bmay be mechanically attached to either surfaces 204, 206 of main segment 106 or they may be coupled to spar 108 of aircraft wing 100 using any suitable attachment means. In one embodiment, one end of flexure members 112a, 112bfit inside notches in spar 108 and are attached in any suitable mechanical or adhesive manner. The other ends of flexure members 112a, 112bare coupled to surfaces 205, 207 of control surface 104. This connection may be accomplished in any suitable manner. For example, a clevis-type arrangement may be utilized such that a rotatable connection exists.

[0032] Electronic power source 200 may be any suitable electronic power source that provides the required electrical charge to piezoelectric actuators 110a, 110b. Similarly, electronic power drive 202 may be any suitable electronic power drive used with piezoelectric actuators 110a, 110bto regulate the electrical charge applied to piezoelectric actuators 110a, 110bto ensure that any deflection of control surfaces 104 are accurately stabilized.

[0033] FIG. 2A illustrates multiple control surfaces 104 being controlled by a pair of piezoelectric actuation systems 102. One or any number of control surfaces 104 may be utilized according to the teachings of the present invention. Because the small size of the elements involved in the present invention, a number of control surfaces 104 may be feasible. This results in a technical advantage of the present invention in that a smooth control surface deflection having maximum aerodynamic efficiency is achieved. In addition, the simplicity of piezoelectric actuation systems 102 allow multiple piezoelectric actuation systems 102, which enhance safety. Piezoelectric actuation systems 102 translate linear motion of piezoelectric actuators 110a, 110binto a useful rotational motion of one or more control surfaces 104 as described further below in conjunction with FIG. 2B.

[0034] FIG. 2B shows aircraft wing 100 in a deflected position according to one embodiment of the present invention. The following discussion of FIG. 2B describes how piezoelectric actuation systems 102 work. As illustrated by arrow 206, piezoelectric actuator 110aexpands as a result of a first applied electrical charge from electronic power source 200, thereby pushing flexure member 112aoutward. At the same time, piezoelectric actuator 110bcontracts as a result of a second applied electrical charge from electronic power source 200, as illustrated by arrow 208, thereby pulling in second flexure member 112b. The combined action of piezoelectric actuators 110aand 110bcause control surface 104 to rotate upward. Depending on the length of flexure members 112aand 112b, and where piezoelectric actuators 110aand 110bcouple to flexure members 112a, 112b, the amplification of the relatively small displacement of piezoelectric actuators 110a, 110bis amplified to produce useful deflection of control surface 104. The same goes for piezoelectric actuation system 102, which deflects control surface 104 in the same manner as described above. A deflection 204 of control surface 104, denoted by alpha, can be in the range of +/−30°. Because of the fast response time of piezoelectric actuators 110a, 110b, deflection 204 is accomplished very quickly, which aids in the controlling of aircraft 90.

[0035] Conversely, arrows 206 and 208 may be reversed such that piezoelectric actuators 110acontracts and pulls flexure member 112ainward and piezoelectric actuator 110bexpands and pushes flexure member 112boutward. This results in a deflection of control surface 104 in a downward rotational motion.

[0036] FIG. 3 is a flowchart illustrating one method for deflecting an aerodynamic control surface 104 according to one embodiment of the present invention. One end of first flexure member 112ais rotatably coupled to first surface 205 of control surface 104 at step 300. One end of second flexure member 112bis rotatably coupled to second surface 207 of control surface 104aat step 302. First piezoelectric actuator 110ais rotatably coupled to first flexure member 112aat step 304, and second piezoelectric actuator 112bis rotatably coupled to second flexure member 112bat step 306. Electronic power source 200 and electronic power drive 202 are electrically coupled to piezoelectric actuators 110a, 110bat step 308. A first electrical charge is input into first piezoelectric actuator 110aand a second electrical charge is input into second piezoelectric actuator 110bat step 310, which causes piezoelectric actuators 110a, 110bto linearly expand or contract. Thereafter, first and second flexure members 112a, 112b, in conjunction with one another, translate linear motion of first and second piezoelectric actuators 110a, 110binto a rotational motion of control surface 104. This completes one embodiment of deflecting an aerodynamic control surface 104 according to one embodiment of the present invention.

[0037] Although embodiments of the invention and their advantages are described in detail, a person skilled in the art could make various alternations, additions, and omissions without departing from the spirit and scope of the present invention as defined by the appended claims. For example, piezoelectric actuation systems 102 can be used in contexts other than aircrafts, such as aerospace vehicles and aquatic vehicles.