Patent Application
20210380221
This disclosure relates in general to the field of aircraft, and more particularly, to flight control.
This section provides background information to facilitate a better understanding of the various aspects of the disclosure. It should be understood that the statements in this section of this document are to be read in this light, and not as admissions of prior art.
Rotorcraft rotors are traditionally controlled by varying the revolutions per minute or by varying pitch. Controlling RPM or varying pitch requires compromises to optimize performance in specific flight regimes, i.e., hovering versus forward flight.
An exemplary continuous variable pitch rotor system includes a blade extending radially from a hub along a longitudinal axis, the blade is rotationally coupled to the hub to permit limited rotation of the blade about the longitudinal axis in response to a change in a rotational speed of the hub. In some embodiments, the blade is held in a radially fixed position relative to the hub. In some embodiments, the blade is permitted to translate radially.
An exemplary aircraft includes a continuous variable pitch rotor coupled to a fuselage and including a hub rotationally driven by a motor and a blade extending radially from the hub along a longitudinal axis, the blade rotationally coupled to the hub to permit limited rotation of the blade about the longitudinal axis in response to a change in a rotational speed of the hub.
Another exemplary aircraft includes a distributed propulsion system having a plurality of rotors, each of the rotors including a variable speed motor coupled to a hub and a blade extending radially from the hub along a longitudinal axis, the blade rotationally coupled to the hub to permit limited rotation of the blade about the longitudinal axis in response to a change in a rotational speed of the hub.
This summary is provided to introduce a selection of concepts that are further described below in the detailed description. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used as an aid in limiting the scope of claimed subject matter.
The disclosure is best understood from the following detailed description when read with the accompanying figures. It is emphasized that, in accordance with standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of various features may be arbitrarily increased or reduced for clarity of discussion.
It is to be understood that the following disclosure provides many different embodiments, or examples, for implementing different features of various illustrative embodiments. Specific examples of components and arrangements are described below to simplify the disclosure. These are, of course, merely examples and are not intended to be limiting. For example, a figure may illustrate an exemplary embodiment with multiple features or combinations of features that are not required in one or more other embodiments and thus a figure may disclose one or more embodiments that have fewer features or a different combination of features than the illustrated embodiment. Embodiments may include some but not all the features illustrated in a figure and some embodiments may combine features illustrated in one figure with features illustrated in another figure. Therefore, combinations of features disclosed in the following detailed description may not be necessary to practice the teachings in the broadest sense and are instead merely to describe particularly representative examples. In addition, the disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not itself dictate a relationship between the various embodiments and/or configurations discussed.
In the specification, reference may be made to the spatial relationships between various components and to the spatial orientation of various aspects of components as the devices are depicted in the attached drawings. However, as will be recognized by those skilled in the art after a complete reading of the present application, the devices, members, apparatuses, etc. described herein may be positioned in any desired orientation. Thus, the use of terms such as “inboard,” “outboard,” “above,” “below,” “upper,” “lower,” or other like terms to describe a spatial relationship between various components or to describe the spatial orientation of aspects of such components should be understood to describe a relative relationship between the components or a spatial orientation of aspects of such components, respectively, as the device described herein may be oriented in any desired direction. As used herein, the terms “connect,” “connection,” “connected,” “in connection with,” and “connecting” may be used to mean in direct connection with or in connection with via one or more elements. Similarly, the terms “couple,” “coupling,” and “coupled” may be used to mean directly coupled or coupled via one or more elements.
Aircraft 100 includes a main rotary system 102 carried by a fuselage 104. Rotor blades 106 of main rotary system 102 provide flight. Rotor blades 106 may be controlled by multiple controllers within fuselage 104. For example, during flight, a pilot can manipulate controllers 105, 107 for changing a pitch angle of rotor blades 106 and to provide vertical, horizontal and yaw flight control. In some embodiments, main rotary system 102 may be configured as continuous variable rotor system whereby the pitch angle of rotor blades 106 are changed in response to a change in the rotational speed of main rotary system 102. Aircraft 100 has a tail boom 108, which supports distributed propulsion system 110. Each of rotors 112 may be operated individually or in groups. Variable speed motors 114, can be operated individually or in groups at different speeds and in different directions, i.e., positive and negative speed, to provide the required thrust and to avoid or mitigate motor speed dead bands, to avoid yaw authority discontinuity at low rotor RPM, and/or resonant frequency conditions between the rotors and the aircraft structure or the rotor itself, and/or to mitigate tonal frequencies in the acoustic signature of distributed propulsion system 110.
It should be appreciated that aircrafts 100 are merely illustrative of a variety of aircraft that can implement the embodiments disclosed herein. Indeed, continuous variable pitch rotors 112 may be implemented on any aircraft and distributed propulsion system 110 may be implemented on any aircraft with two or more rotors. Other aircraft implementations can include hybrid aircraft, tiltrotor aircraft, tiltwing aircraft, quad tiltrotor aircraft, unmanned aircraft, gyrocopters, airplanes, helicopters and the like. It should be appreciated that even though aircraft are particularly well suited to implement the embodiments of the present disclosure, non-aircraft vehicles and devices can also implement the embodiments.
Continuous variable pitch rotor system 112 includes a hub 118 and a blade 116 extending radially from hub 118. Blade 116 extends along longitudinal axis 124 from a shaft end 128 through a blade portion 130. Shaft end 128 is rotationally coupled with hub 118 to permit limited rotation of blade 116 about longitudinal axis 124 in response to the change in rotational speed, e.g., RPMs, of hub 118. Accordingly, output of continuous variable pitch rotor system 112 can be controlled by simultaneously changing RPM and blade pitch.
In an example, shaft end 128 is rotationally coupled to hub 118 by a follower 132 and guide 134 arrangement. For example, a follower 132 engaged with a guide 134 in a manner such that relative movement between follower 132 and guide 134 rotates blade 116 relative to longitudinal axis 124. Follower 132 may be disposed with one of shaft end 128 or hub 118 and guide 134, e.g., track, disposed with the other of shaft end 128 or hub 118. In the illustrated example, follower 132 is a pin and guide 134 is a slot or groove. Various structures may be utilized as a follower and guide as will be understood by those skilled in the art with benefit of this disclosure.
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Conditional language used herein, such as, among others, “can,” “might,” “may,” “e.g.,” and the like, unless specifically stated otherwise, or otherwise understood within the context as used, is generally intended to convey that certain embodiments include, while other embodiments do not include, certain features, elements and/or states. Thus, such conditional language is not generally intended to imply that features, elements and/or states are in any way required for one or more embodiments or that one or more embodiments necessarily include such elements or features.
The term “substantially,” “approximately,” and “about” is defined as largely but not necessarily wholly what is specified (and includes what is specified; e.g., substantially 90 degrees includes 90 degrees and substantially parallel includes parallel), as understood by a person of ordinary skill in the art. The extent to which the description may vary will depend on how great a change can be instituted and still have a person of ordinary skill in the art recognized the modified feature as still having the required characteristics and capabilities of the unmodified feature. In general, but subject to the preceding, a numerical value herein that is modified by a word of approximation such as “substantially,” “approximately,” and “about” may vary from the stated value, for example, by 0.1, 0.5, 1, 2, 3, 4, 5, 10, or 15 percent.
The foregoing outlines features of several embodiments so that those skilled in the art may better understand the aspects of the disclosure. Those skilled in the art should appreciate that they may readily use the disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments introduced herein. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the disclosure and that they may make various changes, substitutions, and alterations without departing from the spirit and scope of the disclosure. The scope of the invention should be determined only by the language of the claims that follow. The term “comprising” within the claims is intended to mean “including at least” such that the recited listing of elements in a claim are an open group. The terms “a,” “an” and other singular terms are intended to include the plural forms thereof unless specifically excluded.
