Patent Application
20200122832
The present disclosure relates to multicopters and, more particularly, to an improved design for a multicopter with reduced drag and power, resulting in increased performance.
The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
In a typical multicopter, a plurality of rotors are provided and arranged substantially equidistant and symmetrically from the center of gravity of the multicopter. For example, a quadcopter (a multicopter with four rotors) may arrange its rotors in an X-configuration. Typically, the locations of the rotors are constrained such that specific combinations of changes in rotor thrust will individually affect a roll, pitch, or yaw torque with no cross coupling of these axes. Further, the plane of the rotors may be fixed in the sense that they do not change orientation (or “tilt”) in relation to the body of the multicopter. In this manner such multicopters can be easily controlled to move in forward, backward, and sideward directions, as well as ascend and descend, by merely changing the speed of rotation of the individual rotors. Furthermore, yaw control may be provided in a similar manner.
For example, to provide forward movement the multicopter may decrease the speed of the rotors in the front (or “fore”) and correspondingly increase the speed of the rotors in the rear (or “aft”). As a result of such adjustments, the multicopter will tilt or tip forward and the rotors will provide a forward thrust to the multicopter. As the multicopter is tilted, the speed of the rotors may be increased to compensate for the lift force that has been translated to forward thrust in order to provide a substantially constant altitude. The tilt of the multicopter will generally increase as the speed of forward (or other directional) movement is increased as the thrust related to the speed of the rotors and the tilt.
As the multicopter tilts, however, the drag on the multicopter will increase as the profile of the body is more exposed to the air resistance. Further, the tilt of the rotors may result in negative interference of the air flow between the fore and aft rotors. As an example, the wake vorticity of the fore rotors may negatively interfere with the aft rotors, thereby resulting in an increase of power consumption during cruising.
Accordingly, it would be desirable to provide an improved design that addresses the above noted and other deficiencies of conventional multicopter design.
In various implementations of the present disclosure, an aircraft with an improved design is disclosed. The aircraft can include a fuselage, a plurality of booms extending from the fuselage, and a plurality of rotors coupled to the fuselage via the plurality of booms. The fuselage can define a longitudinal axis extending in a longitudinal direction from a fore to an aft of the aircraft and a spanwise axis extending in a spanwise direction normal to the longitudinal direction in a plane of the fuselage. The fuselage can also have a first side opposite a second side. At least one boom of the plurality of booms can extend from each of the first side and the second side of the fuselage. Further, the plurality of rotors can comprise at least a pair of rotors arranged on each of the first side and the second side of the fuselage. Each pair of rotors can include a fore rotor and an aft rotor, and each rotor can define an axis of rotation at a rotor hub and be configured to rotate around its axis of rotation to define a circular rotor path. Additionally, each rotor can be configured to tilt its corresponding axis of rotation.
In each pair of rotors, the fore rotor can be spaced from the fuselage by a fore distance in the spanwise direction and the aft rotor can be spaced from the fuselage by an aft distance in the spanwise direction different than the fore distance. In each pair of rotors, the fore distance and the aft distance can be selected such that the circular rotor paths of the fore and aft rotors partially overlap along the spanwise direction.
In additional or alternative implementations, the present disclosure is related to another aircraft with an improved design. The aircraft can include a fuselage, a plurality of booms extending from the fuselage, a plurality of rotors coupled to the fuselage via the plurality of booms, a plurality of electric motors to independently power the plurality of rotors, and a flight control processor configured to control tilting and speed of rotation of the plurality of rotors. The fuselage can define a longitudinal axis extending in a longitudinal direction from a fore to an aft of the aircraft and a spanwise axis extending in a spanwise direction normal to the longitudinal direction in a plane of the fuselage. Further, the fuselage can have a first side opposite a second side. At least one boom of the plurality of booms can extend from each of the first side and the second side of the fuselage.
The plurality of rotors can comprise at least a pair of rotors arranged on each of the first side and the second side of the fuselage, and each rotor can be configured to tilt its corresponding axis of rotation. Each pair of rotors can include a fore rotor and an aft rotor. Each rotor can define an axis of rotation at a rotor hub and be configured to rotate around its axis of rotation to define a circular rotor path. The flight control processor can control the tilting and speed of rotation of the plurality of rotors such that the fuselage is maintained within five degrees of level during cruising of the aircraft. Furthermore, in each pair of rotors, the fore rotor can be spaced from the fuselage by a fore distance in the spanwise direction and the aft rotor can be spaced from the fuselage by an aft distance in the spanwise direction different than the fore distance. The fore distance and the aft distance can be selected such that the circular rotor paths of the fore and aft rotors partially overlap along the spanwise direction.
Further areas of applicability of the present disclosure will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the disclosure.
The present disclosure will become more fully understood from the detailed description and the accompanying drawings, wherein:
As previously discussed, a typical multicopter (which sometimes may be referred to as a drone) includes a plurality of rotors that are arranged symmetrically and substantially equidistant from the center of gravity of the multicopter. Such multicopters are designed such that they can be easily controlled to move forward, backward, and sideward, as well as ascend/descend and rotate about the vertical axis (yaw), by merely changing the speed of rotation of the individual rotors. For example only, in order to provide forward movement, the multicopter may decrease the speed of the rotors in the front (or “fore”) and correspondingly increase the speed of the rotors in the rear (or “aft”). As a result of such adjustments, the multicopter will tilt or tip forward and the rotors will provide a forward thrust to the multicopter. As the multicopter is tilted, the speed of the rotors may be balanced to compensate for the lift force that has been translated to forward thrust in order to provide a substantially constant altitude. The tilt of the multicopter will generally increase as the speed of forward (or other directional) movement is increased as the thrust is related to the speed of the rotors and the tilt.
As the multicopter tilts, however, the drag on the multicopter will increase as the profile of the body is more exposed to the air resistance. Further, the tilt of the rotors may result in negative interference of the air flow between the fore and aft rotors. As an example, the wake vorticity of the fore rotors may negatively interfere with the aft rotors, thereby resulting in an increase of power consumption during cruising.
With reference to
One measurement of the induced drag (or induced power) of a multicopter is an estimation of the energy left in the wake of the multicopter as measured in a plane perpendicular to the motion of the multicopter. This perpendicular plane is referred to as the Trefftz plane and the estimation is commonly referred to as Trefftz Plane Analysis. With reference to
A side view of two of the rotors 220 of the multicopter 200 is shown in
With reference to
The plurality of rotors 320 can include at least a pair of rotors 320 arranged on each of the first and second sides 312, 314 of the fuselage 310. For example only, the illustrated multicopter 300 is shown as having four rotors 320 and corresponding booms 330. It should be appreciated, however, that other configurations of the multicopter 300 are within the scope of the present disclosure. Such additional configurations include, but are not limited to, a single boom 330 with a pair or multiple pairs of rotors 320 on each side 312, 314 of the fuselage 310, and a fuselage 310 with eight total rotors 320 (four on each side) and one or more booms on each side 312, 314. While the described example multicopter 300 is shown as having a single rotor for each rotor 320 shown, the teachings of the present disclosure are applicable, mutatis mutandis, to multicopter designs that utilize groups of rotors 320 that are “stacked” or otherwise grouped in pairs and the rotors spin opposite each other about the same axis.
The pair of rotors 320 on each side 312, 314 of the multicopter 300 shown in
Each of the rotors 320 will be spaced from the fuselage 310 of the multicopter 300 by a distance. In each pair of rotors 320, the fore rotor 320-F will be spaced from the fuselage 310 in the spanwise direction S by a fore distance Df and the aft rotor 320-A will be spaced from the fuselage 310 in the spanwise direction S by an aft distance Da. The fore distance Df and the aft distance Da can be different such that the fore rotor 320-F and the aft rotor 320-A do not completely overlap in the longitudinal direction L.
Each rotor 320 can define a rotor path 350 that can be defined as the path of travel of the rotor 320 through space as the multicopter 300 moves in direction D. For example only,
With particular reference to
In order to provide the beneficial interference described above, the fore distance Df and the aft distance Da can be selected to provide the appropriate overlap amount 360 of the rotor paths 350 in the spanwise direction S. In some aspects, the overlap amount 360 can be between 0 and 50% of the length of the rotor 320. In other examples, the overlap amount 360 can be between 18 and 30% of the length of the rotor 320. It should be appreciated, however, that other overlap amounts 360 can be utilized and still fall within the scope of the present disclosure.
In some aspects, the multicopter 300 can also include a flight control processor 370 and/or a radio receiver 380. The flight control processor 370 can be configured to automatically control the tilting and speed of rotation of each of the plurality of rotors 320, e.g., based on control instructions. The control instructions can be output from a remote control (not shown) of a user and received by the radio receiver 380. Furthermore, the flight control processor 370 can receive the control instructions from radio receiver 380. It should be appreciated that the multicopter 300 can be controlled in other manners than the above.
Movement of the multicopter 300 of the present disclosure can be achieved by controlling the speed of rotation and tilt of the axes of rotation 324 of the rotors 320. In various implementations, the flight control processor 370 can control the tilting and speed of rotation of the plurality of rotors 320. For example only, the multicopter 300 can further include a plurality of electric motors (not shown) to independently power (e.g., rotate) the plurality of rotors 320 and a plurality of servos or other motion control mechanisms (not shown) to control the tilt of the rotors 320.
Because of the asymmetrical configuration of the rotors 320 in the multicopter 300, typical multicopter control strategies may be insufficient to properly provide flight control. Accordingly, yaw control for the multicopter 300 may be provided by tilting the plurality of rotors 320, e.g., in an asymmetrical fashion. Further, forward and rear motion of the multicopter 300 may be controlled by tilting the plurality of rotors 320. Pitch and roll control, as an example, may be provided by modulating power delivered to the plurality of rotors 320.
In various implementations of the present disclosure, the total drag of the multicopter 300 may be further reduced through various design and control arrangements. Because the rotors 320 can be tilted independently of the booms 330 and fuselage 310, and the multicopter 300 itself may be able to better maintain a constant attitude during flight/cruising. Therefore, the fuselage 310 and/or booms 330 can be configured to have a more aerodynamic profile in the intended attitude, thereby reducing the aerodynamic drag during flight. For example only, the flight control processor 370 may automatically control the tilting and speed of the rotors 320 such that the fuselage 310 is maintained within five degrees of level during cruising.
Example embodiments are provided so that this disclosure will be thorough, and will fully convey the scope to those who are skilled in the art. Numerous specific details are set forth such as examples of specific components, devices, and methods, to provide a thorough understanding of embodiments of the present disclosure. It will be apparent to those skilled in the art that specific details need not be employed, that example embodiments may be embodied in many different forms and that neither should be construed to limit the scope of the disclosure. In some example embodiments, well-known procedures, well-known device structures, and well-known technologies are not described in detail.
The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting. As used herein, the singular forms “a,” “an,” and “the” may be intended to include the plural forms as well, unless the context clearly indicates otherwise. The term “and/or” includes any and all combinations of one or more of the associated listed items. The terms “comprises,” “comprising,” “including,” and “having,” are inclusive and therefore specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. The method steps, processes, and operations described herein are not to be construed as necessarily requiring their performance in the particular order discussed or illustrated, unless specifically identified as an order of performance. It is also to be understood that additional or alternative steps may be employed.
Although the terms first, second, third, etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms may be only used to distinguish one element, component, region, layer or section from another region, layer or section. Terms such as “first,” “second,” and other numerical terms when used herein do not imply a sequence or order unless clearly indicated by the context. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the example embodiments.
As used herein, the term processor or module may refer to, be part of, or include: an Application Specific Integrated Circuit (ASIC); an electronic circuit; a combinational logic circuit; a field programmable gate array (FPGA); a processor or a distributed network of processors (shared, dedicated, or grouped) and storage in networked clusters or datacenters that executes code or a process; other suitable components that provide the described functionality; or a combination of some or all of the above, such as in a system-on-chip. The term module may also include memory (shared, dedicated, or grouped) that stores code executed by the one or more processors.
Unless specifically stated otherwise as apparent from the above discussion, it is appreciated that throughout the description, discussions utilizing terms such as “processing” or “computing” or “calculating” or “determining” or “displaying” or the like, refer to the action and processes of a computer system, or similar electronic computing device, that manipulates and transforms data represented as physical (electronic) quantities within the computer system memories or registers or other such information storage, transmission or display devices.
The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.
This application claims the benefit of U.S. Provisional Application No. 62/747,302, filed on Oct. 18, 2018. The disclosure of the above application is incorporated herein by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 62747302 | Oct 2018 | US |
