Compact and Redundant Method for Powering Flight Control Surface from Within Fuselage
Systems and methods for actuating a control surface which is pivotably coupled to a trailing edge of an aircraft wing. The control surface actuation system has a compact footprint and high capability. The control surface actuation system includes a rotatable torque shaft that is coupled (by means of meshed surfaces) to the control surface so that rotation of the torque shaft by a deflection angle causes the control surface to pivot by an equal deflection angle. Rotation of the torque shaft is actuated by a pair of redundant mutually opposing actuation mechanisms. The redundant actuation mechanisms are situated inside of the fuselage, while the torque shaft is disposed partly inside the fuselage and partly inside the control surface.
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The present disclosure relates in general to systems and methods for actuating control surfaces of a vehicle. More particularly, the disclosure relates to control surface actuation systems which are disposed inside the fuselage of an aircraft.
Aerodynamic flight control surfaces, such as flaps, elevators, and rudders, have an aerodynamic cross-sectional profile that is typically formed by connecting an upper skin to a lower skin proximate both the leading edge and the trailing edge of the flight control surface. The wings and stabilizers in high-performance aircraft are thin, that is, the distance between the top and bottom of the outer mold line at the control surface hinge line is small. Thin-wing aircraft create a challenge for spatial integration of actuation control systems with conventional piston-type linear actuators. A method for powering a flight control surface which reduces the footprint of and increases the reliability of such piston-type linear actuators would be a beneficial improvement in the state of the art.
SUMMARYThe subject matter disclosed in some detail below is directed to methods for actuating flight control surfaces by means of a torque shaft drive system which is disposed inside the fuselage of a vehicle (e.g., an aircraft). The torque shaft is partly disposed inside the fuselage and partly disposed outside the fuselage, including a portion disposed inside the control surface. The combination of a torque shaft drive system and a torque shaft will be collectively referred to herein as a “control surface actuation system”. The control surface actuation system disclosed herein is configured to provide a compact footprint and high capability. Rotation of the torque shaft is actuated by a pair of redundant mutually-opposing actuation mechanisms which are situated inside the fuselage in a partly overlapping spatial relationship.
In accordance with some embodiments, each of the two actuation mechanisms is a piston-type linear actuator which is operatively coupled to the torque shaft by means of a respective crank arm that may be splined to or fastened to the torque shaft. Each crank arm converts displacement of the associated piston-type linear actuator into rotation of the torque shaft. Each crank arm is capable of driving the control surface independently to provide drive system redundancy. When the actuation mechanisms are moved in opposite directions concurrently (one extends and the other retracts), the crank arms rotate in the same direction. Both actuation mechanisms are balanced to provide equal retraction and extension capabilities. When both actuation mechanisms are fully functional, one actuation mechanism pushes one crank arm while the other actuator mechanism pulls the other crank arm, thereby causing the torque shaft to rotate and the control surface to deflect to a commanded angle. The control surface actuation system proposed herein further includes a pair of reaction links which are coupled to a bulkhead by means of respective kick links to maintain a load loop. The pair of reaction links partly overlap each other to maintain a very compact package that allows for use of this concept in several instances where space is limited and a fairing is not wanted. In addition, each reaction link is pivotably coupled to the torque shaft at two locations to stabilize the associated actuation mechanism.
Although various embodiments of systems and methods for actuating a flight control surface will be described in some detail below, one or more of those embodiments may be characterized by one or more of the following aspects.
One aspect of the subject matter disclosed in detail below is a system for driving rotation of a torque shaft, the system comprising: a first linear actuator comprising a first cylinder and a first piston rod end which is displaceable relative to the first cylinder; a first crank arm which is pivotably coupled (for example, by means of a pivot joint) to the first piston rod end and coupled to drive rotation of the torque shaft; a first reaction link which is pivotably coupled (for example, by means of a rotary bearing) to the torque shaft and to the first cylinder; a second linear actuator comprising a second cylinder and a second piston rod end which is displaceable relative to the second cylinder; a second crank arm which is pivotably coupled to the second piston rod end and coupled to drive rotation of the torque shaft; and a second reaction link which is pivotably coupled to the torque shaft and to the second cylinder. The first reaction link partly overlaps the second reaction link, thereby reducing the footprint of the actuation system. The linear actuators, crank arms, and reactions links are disposed within a fuselage of the aircraft.
Another aspect of the subject matter disclosed in detail below is a method for driving rotation of a torque shaft, the method comprising: (a) rotatably coupling a first reaction link to the torque shaft at first and second axial locations; (b) coupling the first reaction link to a bulkhead by way of a first kick link; (c) rotatably coupling a second reaction link to the torque shaft at third and fourth axial locations, wherein the third axial location is between the first and second axial locations, and the second axial location is between the third and fourth axial locations; (d) coupling the second reaction link to the bulkhead by way of a second kick link; (e) pivotably coupling a first cylinder of a first linear actuator to the first reaction link; (f) coupling one end of a first crank arm to the torque shaft at a fifth axial location between the second and third axial locations; (g) pivotably coupling another end of the first crank arm to a first piston rod end of the first linear actuator; (h) pivotably coupling a second cylinder of a second linear actuator to the second reaction link; (i) coupling one end of a second crank arm to the torque shaft at a sixth axial location between the second and fifth axial locations; (j) pivotably coupling another end of the second crank arm to a second piston rod end of the second linear actuator; and (k) controlling the first and second linear actuators so that the first linear actuator extends while the second linear actuator retracts, thereby causing the first and second crank arms to rotate in a same direction and the torque shaft to rotate
A further aspect of the subject matter disclosed in detail below is an aircraft comprising a fuselage comprising a bulkhead, an airfoil-shaped member attached to the fuselage, a control surface pivotably coupled to the airfoil-shaped member, and a control surface actuation system operatively coupled to the control surface, wherein the control surface actuation system comprises a torque shaft which is coupled to drive rotation of the control surface, and a torque shaft drive system which is coupled to drive rotation of the torque shaft. The torque shaft drive system comprises: (a) a torque shaft which is coupled to drive rotation of the control surface; (b) a first linear actuator comprising a first cylinder and a first piston rod end which is displaceable relative to the first cylinder; (c) a first crank arm which is pivotably coupled to the first piston rod end and coupled to drive rotation of the torque shaft; (d) a first reaction link which is pivotably coupled to the torque shaft and to the first cylinder; (e) a second linear actuator comprising a second cylinder and a second piston rod end which is displaceable relative to the second cylinder; (f) a second crank arm which is pivotably coupled to the second piston rod end and coupled to drive rotation of the torque shaft; (g) a second reaction link which is pivotably coupled to the torque shaft and to the second cylinder; (h) a first kick link which is pivotably coupled to the first reaction link and to the bulkhead; and (i) a second kick link which is pivotably coupled to the second reaction link and to the bulkhead. The first and second linear actuators, first and second crank arms, first and second reactions links, and first second kick links are disposed inside the fuselage. The aircraft may further comprise a flight control system configured to send commands for controlling the first and second linear actuators so that the first linear actuator extends while the second linear actuator retracts, thereby causing the first and second crank arms to rotate in a same direction
Other aspects of systems and methods for actuating a flight control surface are disclosed below.
The features, functions and advantages discussed in the preceding section may be achieved independently in various embodiments or may be combined in yet other embodiments. Various embodiments will be hereinafter described with reference to drawings for the purpose of illustrating the above-described and other aspects. None of the diagrams briefly described in this section are drawn to scale.
Reference will hereinafter be made to the drawings in which similar elements in different drawings bear the same reference numerals.
DETAILED DESCRIPTIONIllustrative embodiments of systems and methods for actuating a flight control surface are described in some detail below. However, not all features of an actual implementation are described in this specification. A person skilled in the art will appreciate that in the development of any such actual embodiment, numerous implementation-specific decisions must be made to achieve the developer's specific goals, such as compliance with system-related and business-related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming, but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure.
The following detailed description discloses an embodiment of a compact and redundant control surface actuation system suitable for actuating deflection of a flap pivotably coupled to the trailing edge of a wing. However, similarly designed control surface actuation systems may be used to actuate deflection of other types of control surfaces, such as an elevator pivotably coupled to the trailing edge of a horizontal stabilizer, a rudder pivotably coupled to the trailing edge of a vertical stabilizer, or any other control disposed situated in proximity to the fuselage of the aircraft. A control surface is a candidate for actuation by a system disposed inside the fuselage provided that the aircraft design allows the control surface to be coupled to the intra-fuselage actuation system by means of a torque shaft.
The aircraft components which support the torque shaft 12 include three torque shaft support fittings 36a-36c, two of which are shown in
In addition, the front spar 46 of the control surface 6 is configured with splined openings that receive respective splined portions of the torque shaft 12. (One example of such splining will be described in some detail later with reference to
The torque shaft 12 is driven to rotate by the torque shaft drive system 8. The torque shaft drive system 8 includes two redundant mutually-opposed torque shaft drive mechanisms which are coupled to the torque shaft 12 and to the bulkhead 32. Each redundant torque shaft drive mechanism includes a respective crank arm 14a or 14b, a respective piston-type linear actuator 16a or 16b, a respective reaction link 26a or 26b, and a respective kick link 28a or 28b (kick link 28a is not visible in
More specifically, the first torque shaft drive mechanism includes a piston-type linear actuator 16a (for example, a hydraulic actuator or a pneumatic actuator) comprising a cylinder 18, a piston (not visible in
Similarly, the second torque shaft drive mechanism includes a piston-type linear actuator 16b (for example, a hydraulic actuator or a pneumatic actuator) comprising a cylinder 18, a piston (not visible in
As depicted in
In accordance with one embodiment, each of piston-type linear actuators 16a and 16b is a hydraulic actuator. The manifold 22a is configured with solenoid valves which may be selectively opened or closed such that a fluid moving in manifold 22a may control the position of the piston inside the cylinder 18 of piston-type linear actuator 16a. At the same time, manifold 22b controls the position of the piston inside the cylinder 18 of piston-type linear actuator 16b. The piston rods 20 of piston-type linear actuators 16a and 16b are operatively coupled to the torque shaft 12 by means of crank arms 14a and 14b respectively. The crank arms 14a and 14b may be splined to or fastened to the torque shaft 12.
The crank arms 14a and 14b convert displacement of the piston-type linear actuators 16a and 16b into rotation of the torque shaft 12. When one linear actuator is extended and the other linear actuator is retracted, the crank arms 14a and 14b rotate in the same direction. Both actuation mechanisms are balanced to provide equal retraction and extension capabilities. Thus, each crank arm 14a and 14b is capable of driving the control surface 6 independently to provide drive system redundancy. When both actuation mechanisms are fully functional, one actuation mechanism pushes one crank arm while the other actuator mechanism pulls the other crank arm, thereby causing the torque shaft 12 to rotate and the control surface 6 to deflect. The reaction links 26a and 26b and the kick links 28a and 28b transfer reaction loads from the torque shaft 12 to the bulkhead 32 during control surface deflection.
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In addition, the crank arm 14a is coupled to torque shaft 12 at a fifth axial location between the second and third axial locations (in other words, crank arm 14a is between bearings 48b and 48c), while crank arm 14b is coupled to torque shaft 12 at a sixth axial location between the second and fifth axial locations (in other words, crank arm 14b is between bearing 48b and crank arm 14a). Because each crank arm is axially centered with respect to the associated reaction link, the axial offset of crank arms 14a and 14b means that the reaction links 26a and 26b overlap only partially (as best seen in
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As further seen in
In the drive system described in detail above, drive system redundancy is provided by two separate actuators and mechanisms attached to the torque shaft via two separate cranks, each crank being capable of driving the control surface. Redundancy is also provided by constructing a torque shaft that is a tube within a tube, each tube being capable of driving the control surface to deflect up or down. Both actuators are balanced to have equal retraction and extension capabilities. In the example depicted in
In accordance with various embodiments, gaps are provided between the inner and outer tubes of the respective segments. Each gap is a designed-in gap that is used to allow for simple assembly. The gaps may be maintained through several methods.
For one specific application, all tubes are made of steel in order to meet corrosion resistance and strength specifications. All four tubes could be made of the same material but would need to be different thicknesses to accommodate for the drop in diameter from outer to inner tube in the event of a failure. If the tubes were different materials, the thicknesses across the four tubes could be around the same thickness.
The flight controller 40 may comprise one or more signal or data processing devices. Such devices typically include a processor or a computing device, such as a general-purpose central processing unit, a microcontroller, a reduced instruction set computer processor, an application-specific integrated circuit, a programmable logic circuit, a field-programmable gate array, a digital signal processor, and/or any other circuit or processing device capable of executing the functions described herein. The methods described herein may be encoded as executable instructions embodied in a non-transitory tangible computer-readable storage medium, including, without limitation, a storage device and/or a memory device. Such instructions, when executed by a processing device, cause the processing device to issue electrical signals controlling the states of the solenoid valves. The above examples are exemplary only, and thus are not intended to limit in any way the ordinary definitions and/or meanings of the terms “processor” and “computing device”.
While systems and methods for actuating a control surface have been described with reference to various embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the teachings herein. In addition, many modifications may be made to adapt the concepts and reductions to practice disclosed herein to a particular situation. Accordingly, it is intended that the subject matter covered by the claims not be limited to the disclosed embodiments.
Claims
1. A system for driving rotation of a torque shaft, the system comprising:
- a first linear actuator comprising a first cylinder and a first piston rod end which is displaceable relative to the first cylinder;
- a first crank arm which is pivotably coupled to the first piston rod end and coupled to drive rotation of the torque shaft;
- a first reaction link which is pivotably coupled to the torque shaft and to the first cylinder;
- a second linear actuator comprising a second cylinder and a second piston rod end which is displaceable relative to the second cylinder;
- a second crank arm which is pivotably coupled to the second piston rod end and coupled to drive rotation of the torque shaft; and
- a second reaction link which is pivotably coupled to the torque shaft and to the second cylinder.
2. The system as recited in claim 1, wherein the first reaction link partly overlaps the second reaction link.
3. The system as recited in claim 1, further comprising:
- a first kick link which is pivotably coupled to the first reaction link and to a bulkhead of a vehicle; and
- a second kick link which is pivotably coupled to the second reaction link and to the bulkhead.
4. The system as recited in claim 1, wherein the first crank arm is coupled to the torque shaft at a first axial location and the second crank arm is coupled to the torque shaft at a second axial location.
5. The system as recited in claim 4, wherein the first reaction link is pivotably coupled to the torque shaft at third and fourth axial locations, the second reaction link is pivotably coupled to the torque shaft at fifth and sixth axial locations, the fourth axial location is between the second and sixth axial locations, and the fifth axial location is between the first and third axial locations.
6. The system as recited in claim 1, wherein the torque shaft is coupled to a control surface of a vehicle for driving rotation thereof.
7. The system as recited in claim 6, wherein the first and second linear actuators, first and second crank arms, and first and second reactions links are disposed inside a fuselage of the vehicle.
8. A method for driving rotation of a torque shaft, the method comprising:
- (a) rotatably coupling a first reaction link to the torque shaft at first and second axial locations;
- (b) coupling the first reaction link to a bulkhead by way of a first kick link;
- (c) rotatably coupling a second reaction link to the torque shaft at third and fourth axial locations, wherein the third axial location is between the first and second axial locations, and the second axial location is between the third and fourth axial locations;
- (d) coupling the second reaction link to the bulkhead by way of a second kick link;
- (e) pivotably coupling a first cylinder of a first linear actuator to the first reaction link;
- (f) coupling one end of a first crank arm to the torque shaft at a fifth axial location between the second and third axial locations;
- (g) pivotably coupling another end of the first crank arm to a first piston rod end of the first linear actuator;
- (h) pivotably coupling a second cylinder of a second linear actuator to the second reaction link;
- (i) coupling one end of a second crank arm to the torque shaft at a sixth axial location between the second and fifth axial locations;
- (j) pivotably coupling another end of the second crank arm to a second piston rod end of the second linear actuator; and
- (k) controlling the first and second linear actuators so that the first linear actuator extends while the second linear actuator retracts, thereby causing the first and second crank arms to rotate in a same direction and the torque shaft to rotate.
9. The method as recited in claim 8, further comprising coupling the torque shaft to a control surface of a vehicle for driving rotation thereof.
10. The method as recited in claim 9, wherein coupling the torque shaft to the control surface comprises meshing splines on the torque shaft with mating splines formed in a spar of the control surface.
11. The method as recited in claim 9, wherein the first and second linear actuators, first and second crank arms, and first and second reactions links are disposed inside a fuselage of the vehicle.
12. The method as recited in claim 8, wherein:
- step (i) comprises pivotably coupling the first kick link to the bulkhead and to the first reaction link; and
- step (j) comprises pivotably coupling the second kick link to the bulkhead and to the second reaction link.
13. An aircraft comprising a fuselage comprising a bulkhead, an airfoil-shaped member attached to the fuselage, a control surface pivotably coupled to the airfoil-shaped member, and a control surface actuation system operatively coupled to the control surface, wherein the control surface actuation system comprises a torque shaft which is coupled to the control surface for driving rotation thereof, and a torque shaft drive system which is coupled to the torque shaft for driving rotation thereof, wherein the torque shaft drive system comprises:
- a first linear actuator comprising a first cylinder and a first piston rod end which is displaceable relative to the first cylinder;
- a first crank arm which is pivotably coupled to the first piston rod end and coupled to the torque shaft for driving rotation thereof;
- a first reaction link which is pivotably coupled to the torque shaft and to the first cylinder;
- a second linear actuator comprising a second cylinder and a second piston rod end which is displaceable relative to the second cylinder;
- a second crank arm which is pivotably coupled to the second piston rod end and coupled to drive rotation of the torque shaft;
- a second reaction link which is pivotably coupled to the torque shaft and to the second cylinder;
- a first kick link which is pivotably coupled to the first reaction link and to the bulkhead; and
- a second kick link which is pivotably coupled to the second reaction link and to the bulkhead,
- wherein the first and second linear actuators, first and second crank arms, first and second reactions links, and first second kick links are disposed inside the fuselage.
14. The aircraft as recited in claim 13, wherein the first reaction link partly overlaps the second reaction link.
15. The aircraft as recited in claim 13, wherein the first crank arm is coupled to the torque shaft at a first axial location and the second crank arm is coupled to the torque shaft at a second axial location.
16. The aircraft as recited in claim 15, wherein the first reaction link is pivotably coupled to the torque shaft at third and fourth axial locations, the second reaction link is pivotably coupled to the torque shaft at fifth and sixth axial locations, the fourth axial location is between the second and sixth axial locations, and the fifth axial location is between the first and third axial locations.
17. The aircraft as recited in claim 13, wherein a front spar of the control surface comprises first and second pluralities of splines and the torque shaft comprises third and fourth pluralities of splines which are respectively meshed with the first and second pluralities of splines.
18. The aircraft as recited in claim 13, further comprising:
- a torque shaft support fitting that is attached to a rear spar of the airfoil-shaped member outside the fuselage, wherein the torque shaft support fitting comprises an opening through which the torque shaft passes; and
- a bearing disposed in the opening in the torque shaft support fitting and configured to support the torque shaft while allowing the torque shaft to rotate.
19. The aircraft as recited in claim 17, wherein:
- the torque shaft comprises first and second torque shaft segments;
- one end of the first torque shaft segment is inside one end of the second torque shaft segment; and
- the third and fourth pluralities of splines are on an outer surface of the second torque shaft segment.
20. The aircraft as recited in claim 13, further comprising a flight control system configured to send commands to control the first and second linear actuators so that the first linear actuator extends while the second linear actuator retracts, thereby causing the first and second crank arms to rotate in a same direction.
Type: Application
Filed: Feb 7, 2020
Publication Date: Aug 12, 2021
Applicant: The Boeing Company (Chicago, IL)
Inventors: Wilfredo Alvizures (Snohomish, WA), Randall E. Anderson (Stanwood, WA)
Application Number: 16/784,545