The present disclosure relates to rotor/wing aircraft, and more specifically, to apparatus and methods for structurally-integrated conductive conduits for rotor blades.
Active control of rotor blades with the goal of reducing rotor born noise and vibration is an ongoing area of research in the helicopter and rotor-driven aircraft industry. Numerous research papers and scale model tests have predicted and demonstrated the successful reduction of airframe vibration levels and noise through a number of enabling schemes. One such scheme is active control of a hinged trailing edge flap(s) located near the blade tip of a rotor blade. The location and number of flaps relative to the blade tip can affect both the blade vibration level due to the inherent unsteady aerodynamic conditions and the noise generated at the blade tip due to blade vortex interactions depending on the configuration selected.
Successful “on blade” active control rotor systems rely on actuation means to drive the flap. Piezoelectric smart materials are currently being investigated as an actuation means by university, government, and industry-sponsored research. For example, embedded piezoelectric sheets are being investigated as a means to control trailing edge elevons. Embedded piezoelectric fibers are also being investigated to allow dynamic twist variation of a rotor blade. Alternately, discrete piezoelectric actuators coupled with actively controlled rotor blade flaps are disclosed, for example, U.S. Pat. No. 6,135,713 issued to Domzalski et al., U.S. Pat. No. 5,907,211 issued to Hall et al., and U.S. Pat. No. 5,224,826 issued to Hall et al.
Although desirable results have been achieved, technical difficulties have been encountered. For example, traditional surface mount techniques for providing actuator power and for transmitting signals along the rotor blade may be adversely impacted by the extremely hostile vibratory and high g-field environment on the rotor blade and its components. These effects may reduce the usable life of such systems below acceptable levels due to excessive fatigue. Such systems may also undesirably degrade the structural and aerodynamic characteristics of the rotor blade.
Furthermore, efforts directed toward providing power and data signals to embedded piezoelectric actuators in rotor blades generally involve running wiring along a spanwise groove formed within the blade surface as disclosed, for example, in Full Scale Rotor with Piezoelectric Actuated Blade Flaps, 28th European Rotorcraft Forum, Session Dynamics 7, Paper 89, pg 89.7 by Enenkl et al. Additional efforts to develop a more advanced electrical bus system for directing electric power and data or control signals to embedded piezoelectric elements within the rotor blade have shown that low temperature solder joints may be degraded during blade assembly cure operations. Therefore, novel apparatus and methods which at least partially mitigate these undesirable characteristics would be useful.
The present invention is directed to apparatus and methods for structurally-integrated conductive conduits for rotor blades. Apparatus and methods in accordance with the present invention may advantageously provide the ability to transmit power and data signals along a rotor blade to embedded actuators or other devices in a manner that mitigates the effects of high fatigue cyclic strain levels on conductive elements, and that allows the mass and stiffness of the structurally-integrated conductive element assembly to be tailored to achieve the desired blade aeroelastic properties.
In one embodiment, an elongated rotor blade includes a body having a root portion and a distal portion spaced apart from the root portion, a device coupled to the body, and a conduit assembly disposed within the body and extending between the root portion and the device. The conduit assembly includes a main body assembly having at least one of a conductive lead, a fluid line, and an optical fiber disposed within a matrix material, the conduit assembly extending from the root portion to the device. In alternate embodiments, the device may comprise an actuator, a smart actuator, a piezoelectric material, an electromagnetic device, an electromechanical device, a light, and a sensor.
Preferred and alternative embodiments of the present invention are described in detail below with reference to the following drawings.
The present invention relates to apparatus and methods for structurally-integrated conductive conduits for rotor blades. Many specific details of certain embodiments of the invention are set forth in the following description and in
In general, embodiments of structurally-integrated conductive conduits for rotor blades in accordance with the present invention provide the ability to transmit power and data signals along a rotor blade to embedded actuators, sensors, or other devices in a manner that at least partially mitigates the above-noted disadvantages of conventional electrical systems. For example, as described more fully below, embodiments of the present invention may minimize the effects of high fatigue cyclic strain levels on conductive elements to achieve a longer fatigue life, and may allow the tailoring of the mass and stiffness of the structurally-integrated conductive element assembly to achieve the desired rotor blade aeroelastic properties.
More specifically,
As best shown in
A wide variety of matrix materials may be used to form the conductive conduit 120 including, for example, thermosetting resins such as epoxies, polyimides, and phenolics, or thermoplastic resins such as PEI and PEEK. The choice of resin may be limited by the manufacturing processing temperature limits of the selected embedded conductive lead (e.g. wire insulation type), fluid line or optical fiber, etc. Composite matrix fiber materials including, for example, glass, carbon, Kevlar or metallic fibers, etc. in a number of forms, such as continuous rovings or tape, woven mats, discontinuous, chopped, wire or whiskers, etc. can also be used as a matrix material. In one particular embodiment, the matrix material comprises a chopped fiberglass in an epoxy resin. In alternate embodiments, the conductive conduit 120 may support the embedded lead(s) using a matrix resin only, without a reinforcing matrix fiber.
It will be appreciated that the conductive conduit 120 may be fabricated in any one of a number of conventional composite molding or processing techniques; such as, room temperature pour and casting, prepreg hand lay-up and autoclave or press curing, injection molding methods, resin transfer molding, or any other suitable process. The processing method may be a function of the matrix material selected and the embedded conductive lead material, which may impose processing constraints
It will be appreciated that the main assembly body 121 of the conductive conduit 120 may be adapted to suit a particular installation or a particular set of interface requirements. For example, as shown in
Although the conductive conduit 120 shown in
In operation, electrical power may be provided through the master power connector 144 and the power leads 122 of the conductive conduit 120 to the actuator 116. Similarly, control signals and data signals may be transmitted to and received from the actuator 116 via the data leads 124 and the master data connector 148. Thus, using a suitable controller (e.g. a portion of the flight control system of the rotor-driven aircraft), the actuator 116 may be controllably driven to actuate the flap 108 into a desired position, such as to reduce vibration of the rotor blade 100.
Embodiments of structurally-integrated conductive conduits for rotor blades in accordance with the present invention may provide considerable advantages over the prior art. For example, embodiments of the present invention may minimize the effects of high fatigue cyclic strain levels on conductive elements. Because the power leads 122 and the data leads 124 are disposed within the matrix material 126, the fatigue on these conductive elements is reduced and a longer fatigue life may be achieved. Also, the positioning of the leads 122, 124 within the matrix material may allow the tailoring of the mass and stiffness of the structurally-integrated conductive element assembly to achieve the desired rotor blade aeroelastic properties. In other words, by proper selection and formation of the matrix material 126, the structural properties of the rotor blade 100 may be improved in comparison with the prior art. The material properties of the conductive leads in the matrix material may be selected and tailored to provide optimum electrical characteristics and blades stiffness properties when installed and bonded within the rotor blade structure. Furthermore, the integrated design of the conductive conduit 120 with the rotor blade structure geometrically can place the internal wiring as close to the blade flap-wise neutral axis as possible to minimize the effects of high flap bending cyclic strain levels on the embedded conductive elements to achieve a longer fatigue life.
When tailoring the conductive conduit 120 to transmit high-voltage electric power, the use of shielded, single conductor or multi-conductor stranded wire insulated cable allows the use of high-voltage power from noisy sources, such as switching amplifiers, in close proximity to low-voltage instrumentation data signals, in which it is desired to minimize the effects of electrical noise. The ability to place power and data signal conductive leads in close proximity, while selecting the matrix material, allows the tailoring of the mass and stiffness of the conductive conduit 120 to the overall desired blade aeroelastic properties.
It will be appreciated that a variety of alternate embodiments of apparatus and methods in accordance with the present invention may be conceived, and that the invention is not limited to the particular embodiments described above and shown in
Furthermore, alternate embodiments of conductive conduits in accordance with the present invention may be adapted to provide power and data signals to any other desired type of component that may be embedded within or affixed to the rotor blade 100. For example, in alternate embodiments, conductive conduits in accordance with the present invention may be adapted to operate in conjunction with other smart material actuation technologies, including, for example, smart actuators based on magnetostrictive materials and shape memory alloys as generally disclosed in U.S. Pat. No. 6,322,324 issued to Kennedy et al., and in U.S. Pat. No. 6,453,669 issued to Kennedy et al., which patents are incorporated herein by reference. Still further embodiments may be adapted to operate with other methods of on-blade control to influence aerodynamic forces on rotor blades, including deployable leading edge devices, and active flow control using Lorentz force (voice coil) actuators of the type generally disclosed, for example, in U.S. Pat. No. 5,938,404 issued to Domzalski et al. In addition, embodiments of the present invention may be adapted to operate with a variety of conventional devices, such as electromagnetic, electromechanical, and hydraulic devices. For example, one or more of the power leads 122 of the conductive conduit 120 may be replaced with a hydraulic or pneumatic supply line to actuate conventional hydraulic or pneumatic actuators.
Alternate embodiments the present invention may also be used to provide power and/or signals to other on-blade devices, including sensors (e.g. strain gauge devices, accelerometers), lights, or any other suitable devices. Furthermore, one or more of the power leads or data leads may be replaced with an optical fiber for transmitting optical signals to and from an optically-based blade-mounted device.
Embodiments of apparatus and methods for structurally-integrated conductive conduits for rotor blades in accordance with the present invention may be utilized on a wide variety of rotor-driven aircraft. For example,
As further shown in
As described above, the devices 331 on the blade members 328 may be any type of device that requires power or that transmits or receives data signals, including, for example, a light, a sensor (e.g. strain gauge, accelerometer, thermocouple, temperature gauge, etc), a smart material (e.g. a piezoelectric material, magnetostrictive material, a shape memory alloy, etc.), an electromagnetic or electromechanical device, or any other suitable device. Alternately, the devices 331 may be a hydraulic or pneumatic device coupled to hydraulic or pneumatic lines disposed within the conductive conduit 329, or an optically-based device coupled to an optical fiber disposed within the conductive conduit 329. Of course, in further embodiments, the blade member 328 may include a flap, and one or more of the devices 331 may be an actuator or other drive mechanism, as described above with respect to
As further shown in
The aircraft 200 further includes a canard 230 and a tail assembly 232. The canard 230 extends outwardly from each side of the fuselage 202, forwardly of the rotor 206. The trailing edges of the canard 230 include flaperons 234. The tail assembly 232 is conventional with respect to other fixed wing aircraft, and includes a vertical tail portion 236 as well as two horizontal portions 238 extending outwardly from each side of the fuselage 202, rearwardly of the rotor 206. Each of the horizontal portions 238 also includes a flaperon 240.
It should be understood that the invention is not limited to the particular embodiments of rotor blades described above and shown in the accompanying figures, and that a wide variety of blade shapes may be conceived in accordance with the teachings of the present disclosure. More specifically, a wide variety of blades may be conceived having differing degrees of camber, aspect (thickness over chord) ratio, size, or other desired design parameters, and that vary from the representative blades shown in the accompanying figures.
It will also be appreciated that a wide variety of rotor driven aircraft may be conceived that include rotor blades having a structurally-integrated conductive conduit in accordance with alternate embodiments of the present invention, and that the invention is not limited to the particular aircraft embodiments described above and shown in
While preferred and alternate embodiments' of the invention have been illustrated and described, as noted above, many changes can be made without departing from the spirit and scope of the invention. Accordingly, the scope of the invention is not limited by the disclosure of these preferred and alternate embodiments. Instead, the invention should be determined entirely by reference to the claims that follow.
This invention was made with government support under U.S. Government Contract NAS2-01064 awarded by the National Aeronautics and Space Administration. The U.S. Government has certain rights in this invention.