CN113178994A - Two-degree-of-freedom high-pitch torque motor, system and aircraft comprising same - Google Patents

Abstract

The invention provides a two-degree-of-freedom high-tilt torque motor, a system and an aircraft comprising the same. The invention discloses a double-freedom-degree motor which comprises an inner stator, a plurality of inner stator windings, an inner rotor, an outer stator, a plurality of outer stator windings, an outer rotor and a shaft. The inner rotor is spaced apart from and at least partially surrounds the inner stator and includes a plurality of magnets. The outer stator is spaced apart from and at least partially surrounds the inner stator and the inner rotor. The outer rotor is spaced apart from and disposed between the inner rotor and the outer stator and has a plurality of outer rotor protrusions. The shaft is coupled to the inner rotor and the outer rotor.

Description

Two-degree-of-freedom high-pitch torque motor, system and aircraft comprising same

Cross Reference to Related Applications

This application claims the benefit of previously filed indian provisional patent application No. 202011003532 filed on 27/1/2020, which is incorporated herein by reference in its entirety.

Technical Field

The present invention relates generally to multiple degree of freedom motors and, more particularly, to two degree of freedom high pitch torque motors, systems, and aircraft including the same.

Background

With the development of the fields of UAV (unmanned aerial vehicle), unmanned aerial vehicle for air transportation, robotics, office automation, intelligent flexible manufacturing and assembly system, etc., it has become necessary to develop a multi-degree of freedom (DOF) precision actuation system. Conventionally, applications relying on multiple degrees of freedom of motion are typically accomplished by using separate motors/actuators for each axis, which results in complex drive systems and relatively heavy structures.

With the advent of spherical motors, there have been numerous attempts to replace complex multiple degree of freedom assemblies with a single spherical motor assembly. A typical spherical motor consists of a central sphere around which coils, which may be placed orthogonally to each other, are wound. The sphere is surrounded by a multi-pole magnet in the form of an open cylinder. The coil assembly is axially held and held in a vertical position via, for example, metal posts. The outer cylinder is held by the carrier/frame via bearings that allow the cylinder to rotate about its axis. The carrier is also connected to the metal posts of the coil assembly via a second bearing that allows the carrier to be rotatable with the cylinder about one or two additional axes.

Unfortunately, current attempts to apply spherical motors to certain applications, such as UAVs and robots, have resulted in several spherical motor design concepts. Unfortunately, many of these design concepts suffer from certain disadvantages. For example, many concepts exhibit relatively limited torque and precise positioning, particularly on the tilt axis. This is due at least in part to the relatively large air gap between the magnets and the inner spherical stator (due in part to the windings) and the relatively heavy spherical stator. The current concept also exhibits relatively high winding temperatures, relatively complex and time consuming winding patterns.

Therefore, there is a need for a multiple degree of freedom electromagnetic machine that exhibits at least improved generated torque and position accuracy (particularly in the tilt axis), improved heat handling capability, improved speed range, and a simpler coil winding structure than currently known spherical motors. The present invention addresses at least this need.

Disclosure of Invention

This summary is provided to describe selected concepts in a simplified form that are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.

In one embodiment, a two degree of freedom motor includes an inner stator, a plurality of inner stator windings, an inner rotor, an outer stator, a plurality of outer stator windings, an outer rotor, and a shaft. The inner stator has a plurality of inner stator poles extending radially outward. An inner stator winding is wound around the inner stator pole and is operable when energized to generate a first magnetic field. The inner rotor is spaced apart from and at least partially surrounds the inner stator. The inner rotor includes a plurality of magnets and is mounted for rotation about a first axis of rotation. The outer stator is spaced apart from and at least partially surrounds the inner stator and the inner rotor. The outer stator has a plurality of radially inwardly extending outer stator poles. The outer stator winding is wound around the outer stator poles and is operable when energized to generate a second magnetic field. The outer rotor is spaced apart from and disposed between the inner rotor and the outer stator. The outer rotor has a plurality of outer rotor protrusions extending radially outward. The outer rotor is mounted for rotation about a second axis of rotation perpendicular to the first axis of rotation. The shaft is coupled to the inner rotor and the outer rotor and is selectively rotatable with the inner rotor about a first axis of rotation and selectively rotatable with the outer rotor about a second axis of rotation.

In another embodiment, a two degree of freedom motor includes an inner stator, a plurality of inner stator windings, an inner rotor, an outer stator, a plurality of outer stator windings, an outer rotor, a shaft, and a controller. The inner stator has a plurality of inner stator poles extending radially outward. An inner stator winding is wound around the inner stator pole and is operable when energized to generate a first magnetic field. The inner rotor is spaced apart from and at least partially surrounds the inner stator. The inner rotor includes a plurality of magnets and is mounted for rotation about a first axis of rotation. The outer stator is spaced apart from and at least partially surrounds the inner stator and the inner rotor. The outer stator has a first predetermined number of radially inwardly extending outer stator poles. The outer stator winding is wound around the outer stator poles and is operable when energized to generate a second magnetic field. The outer rotor is spaced apart from and disposed between the inner rotor and the outer stator. The outer rotor has a second predetermined number of radially outwardly extending outer rotor protrusions. The outer rotor is mounted for rotation about a second axis of rotation perpendicular to the first axis of rotation. The shaft is coupled to the inner rotor and the outer rotor and is selectively rotatable with the inner rotor about a first axis of rotation and selectively rotatable with the outer rotor about a second axis of rotation. A controller is in operable communication with the inner stator winding and the outer stator winding. The controller is configured to controllably supply current to the inner stator winding and the outer stator winding. The first predetermined number is greater than the second predetermined number.

In another embodiment, an Unmanned Aerial Vehicle (UAV) includes a fuselage, a plurality of propellers rotatable relative to the fuselage, and a plurality of two-degree-of-freedom motors mounted on the fuselage. Each motor is coupled to a different one of the propellers, and each motor includes an inner stator, a plurality of inner stator windings, an inner rotor, an outer stator, a plurality of outer stator windings, an outer rotor, and a shaft. The inner stator has a plurality of inner stator poles extending radially outward. An inner stator winding is wound around the inner stator pole and is operable when energized to generate a first magnetic field. The inner rotor is spaced apart from and at least partially surrounds the inner stator. The inner rotor includes a plurality of magnets and is mounted for rotation about a first axis of rotation. The outer stator is spaced apart from and at least partially surrounds the inner stator and the inner rotor. The outer stator has a plurality of radially inwardly extending outer stator poles. The outer stator winding is wound around the outer stator poles and is operable when energized to generate a second magnetic field. The outer rotor is spaced apart from and disposed between the inner rotor and the outer stator. The outer rotor has a plurality of outer rotor protrusions extending radially outward. The outer rotor is mounted for rotation about a second axis of rotation perpendicular to the first axis of rotation. The shaft is coupled to the inner rotor and the outer rotor and is selectively rotatable with the inner rotor about a first axis of rotation and selectively rotatable with the outer rotor about a second axis of rotation.

Furthermore, other desirable features and characteristics of the two-degree-of-freedom motor, system, and aircraft will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing background.

Drawings

The present invention will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements, and wherein:

FIG. 1 shows a simplified cross-sectional view of one embodiment of a two degree-of-freedom motor;

FIG. 2 shows a plan view of a portion of the two degree-of-freedom motor shown in FIG. 1 (with some features shown as transparent);

FIG. 3 is a plan view of a spin motor that may be used with the two degree of freedom motor shown in FIG. 1;

FIG. 4 shows a plan view of a tilt motor (some features of which are shown as transparent) that may be used in the two degree-of-freedom motor shown in FIG. 1;

FIG. 5 shows a plan view of a rotor that may be used in the tilting motor of FIG. 4;

FIGS. 6 and 7 are plan views of a portion of the two degree-of-freedom motor shown in FIG. 1 (with some features shown as transparent) with the tilt motor in a non-tilted position (FIG. 6) and a tilted position (FIG. 7);

FIG. 8 illustrates a functional block diagram of a multiple degree of freedom control system; and is

Figure 9 illustrates one embodiment of an unmanned aerial vehicle that can include the two degree-of-freedom motor shown in figure 1.

Detailed Description

The following detailed description is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention. As used herein, the word "exemplary" means "serving as an example, instance, or illustration. Thus, any embodiment described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments. All of the embodiments described herein are exemplary embodiments provided to enable persons skilled in the art to make or use the invention and not to limit the scope of the invention which is defined by the claims. Furthermore, there is no intention to be bound by any expressed or implied theory presented in the preceding technical field, background, brief summary or the following detailed description.

Referring to fig. 1 and 2, a simplified cross-sectional and plan view, respectively, of one embodiment of a two degree-of-freedom motor 100 is shown (with some features shown as transparent). As shown therein, the motor 100 includes at least an inner stator 102, a plurality of inner stator windings 104, an inner rotor 106, an outer stator 108, a plurality of outer stator windings 112, and an outer rotor 114. As will become apparent from the description, the inner stator 102 and the inner rotor 106 form a first (or "spin") motor 103, and the outer stator 108 and the outer rotor 114 form a second (or "pitch") motor 105.

The spin motor 103 is shown separate from the two degree of freedom motor 100 and is therefore more clearly shown in figure 3. As clearly seen therein, the inner stator 102 includes a body 302 and a plurality of inner stator poles 304. The inner stator pole 304 extends radially outward from the body 302 and defines a plurality of inner stator slots 306. In the illustrated embodiment, the inner stator 102 is implemented with 18 inner stator poles 304, and thus 18 inner stator slots 306. However, it should be understood that the inner stator 102 may be implemented with more or less than the number of inner stator poles 304 and inner stator slots 306. The inner stator 102 may be formed of any one of a variety of magnetic or non-magnetic materials. Preferably, however, it is formed of a magnetic material, and most preferably a laminated magnetic material. By way of example only, some non-limiting examples of suitable magnetic materials include any of a number of known silicon steels such as M19, M27, M36, and M43, or alloys such as

50 alloy and any of the various known alloys of ASTM a848, or any of the various magnetic ferrous materials such as DT 4C.

Regardless of the number of inner stator poles 304 and inner stator slots 306, the inner stator winding 104 wraps around the inner stator poles 304 and extends through the inner stator slots 306. The inner stator winding 104 may be wound in a concentrated or distributed manner within these inner stator slots 306. In the illustrated embodiment, it is noted that the inner stator winding 104 is implemented as a three-phase winding. However, in other embodiments, the inner stator winding 104 may be implemented with N phases, where N is an integer greater or less than 3. Regardless of the number of phases, the inner stator winding 104 is operable to generate a magnetic field when energized.

With continued reference to FIG. 3, one mayIt is seen that the inner rotor 106 is spaced from the inner stator 102 and at least partially surrounds the inner stator 102. Inner rotor 106 is mounted for rotation about first rotational axis 116-1 (see fig. 1) and includes an inner surface 308, an outer surface 312, and a plurality of magnets 314. The magnets 314 are coupled to the inner surface 308 of the inner rotor 106 and extend radially inward toward the stator poles 304. Inner rotor 106 may be formed from any of a variety of magnetic or non-magnetic materials. Preferably, however, it is formed of a magnetic material. By way of example only, some non-limiting examples of suitable magnetic materials include any of a number of known silicon steels such as M19, M27, M36, and M43, or alloys such as

50 alloy and any of the various known alloys of ASTM a848, or any of the various magnetic ferrous materials such as DT 4C.

Note that the illustrated embodiment is implemented with 22 magnets 314. However, it should be understood that this is merely exemplary, and that there may be more or less than this number of magnets 314. Regardless of the specific number, each magnet 314 is preferably arranged such that half of the magnets 314 have a polarity opposite to that of the other half of the magnets 314 with respect to the inner stator 102. To maximize efficiency, the magnets 314 are preferably implemented using advanced permanent magnets. The magnet 314 may also be implemented using a Halbach array.

Turning now to fig. 4, the tilt motor 105 is shown separate from the two degree of freedom motor 100 and is therefore more clearly shown. Before describing the tilt motor 105 in more detail, it is noted that the outer stator 108 is shown as transparent in fig. 4. This is to allow the interior portions of the outer stator 108, outer stator windings 112, and outer rotor 114 to be visible. This also helps illustrate the relative positioning of the outer stator 108 and the outer rotor 114.

In any event, referring quickly to fig. 1, it can be seen that the outer stator 108 is spaced from and at least partially surrounds the inner stator 102, the inner rotor 106 and the outer rotor 114 and is fixedly mounted to the first mounting structure 125. In some implementationsIn an aspect, the first mounting structure 125 may be, for example, a fuselage of an Unmanned Aerial Vehicle (UAV). Referring back to fig. 4, it can also be seen that the outer stator 108 is at least hemispherical and includes an inner surface 402, an outer surface 404, and a plurality of outer stator poles 406. The outer stator poles 406 extend radially inward from the inner surface 402 of the outer stator toward the outer rotor 114. The outer stator 108 is implemented with a first predetermined number of outer stator poles 406. In the embodiment shown, the first predetermined number is 24; however, it should be understood that the outer stator 108 may be implemented with more or less than the number of outer stator poles 406. The outer stator 108 may be formed from any of a variety of magnetic or non-magnetic materials. Preferably, however, it is formed of a magnetic material, and most preferably a laminated magnetic material. By way of example only, some non-limiting examples of suitable magnetic materials include any of a number of known silicon steels such as M19, M27, M36, and M43, or alloys such as

50 alloy and any of the various known alloys of ASTM a848, or any of the various magnetic ferrous materials such as DT 4C.

Regardless of the specific number of outer stator poles 406, it can be seen that the outer stator winding 112 is wound around the outer stator poles 406 and is operable to generate a second magnetic field when energized. More specifically, the outer stator winding 112 includes a plurality of individual coils 408, each wound around a different one of the outer stator poles 406. Thus, when the single coil 408 is energized, the coil 408 and its wound outer stator pole 406 act as an electromagnet to generate a second magnetic field.

Also, referring back to fig. 1, it can be seen that the outer rotor 114 is spaced from and disposed between the inner rotor 106 and the outer stator 108. Now, as shown more clearly in fig. 5, outer rotor 114 includes an inner surface 502, an outer surface 504, and a plurality of outer rotor protrusions 506. The outer rotor protrusions 506 extend radially outward from the outer surface 504 of the outer rotor 114 toward the outer stator 108. The outer rotor 114 is also mounted for rotation about a second axis of rotation 116-2 (see fig. 1) that is perpendicular to the first axis of rotation 116-1. The manner in which this is achieved is described further below.

The number of outer rotor protrusions 506 may vary, but is preferably a second predetermined number that is less than the first predetermined number of outer stator poles 406. In the embodiment shown, the second predetermined number is 18; however, it should be understood that outer rotor 114 may be implemented with more or less than this number of outer rotor protrusions 506. It should be understood that each of outer rotor protrusions 506 may include a ferrous material or each outer rotor protrusion may include a permanent magnet.

Referring now back to fig. 1, it can be seen that the two degree of freedom motor 100 additionally includes a shaft 118. The shaft 118 extends through the inner stator 102 and has a shaft first end 122 and a shaft second end 124. The shaft first end 122 is rotationally coupled to the second mounting structure 126 via a first bearing structure 128 and is rotatable relative to the second mounting structure 126 about the first axis of rotation 116-1. The second mounting structure 126 is rotationally mounted on the outer stator 108 via an outer rotor bearing assembly 115(115-1, 115-2). Accordingly, shaft 118 is rotatable with outer rotor 114 about second axis of rotation 116-2. The shaft second end 124 is coupled to a load 132. The load 132 may be implemented using any of a variety of types of loads, but in the illustrated embodiment, the load 132 is a propeller.

Shaft 118 is also coupled to inner rotor 106 and outer rotor 114. The shaft 118 is rotatable with the inner rotor 106 about a first axis of rotation 116-1 and, as just noted, is rotatable with the outer rotor 114 about a second axis of rotation 116-2. In the illustrated embodiment, shaft 118 is coupled to inner rotor 106 via mechanical fasteners 134 that are connected to inner rotor 106 and shaft 118 and are disposed between outer rotor 114 and shaft 118 and are spaced 180 degrees apart from each other. The shaft 118 is coupled to the outer rotor 114 via a second bearing structure 136 that is connected to the outer rotor 114 and the shaft 118 to allow the shaft 118 to rotate relative to the outer rotor 114. The shaft 118 is preferably formed of a non-magnetic material, such as aluminum or stainless steel, for example.

With the configuration described herein, when the inner stator winding 104 is energized, the resulting magnetic field causes the inner rotor 106 (and thus the shaft 118) to rotate about the first rotational axis 116-1. As described above, a load 132, such as the illustrated propeller, may be coupled to the shaft 118 to receive torque provided therefrom. More specifically, when the inner stator winding 104 is energized with an Alternating Current (AC) voltage, a lorentz force is generated between the inner stator winding 104 and the magnets 314, which in turn applies a torque to the inner rotor 106 (and thus the shaft 118) causing it to rotate about the first axis of rotation 116-1 (e.g., the spin axis).

Further, by energizing selected ones of the outer stator windings 112, the resulting magnetic field may generate a torque on the outer rotor 114 that will cause the outer rotor 114, and thus the inner stator 102, the inner rotor 106, and the shaft 118, to rotate about the second axis of rotation 116-2. More specifically, when selected coils of the single coils 408 are energized with a DC voltage, the energized coils 408 generate magnetic fluxes that attract (or repel) adjacent outer rotor protrusions 506. This creates a torque on the inner rotor 114 that causes it to rotate about the second axis of rotation 116-2 from the normal non-rotational position shown in fig. 6 to a desired rotational position, such as the rotational position shown in fig. 7. The magnitude and direction of the torque depends on the magnitude and direction of the input current provided to the individual coils 408, and which individual coils 408 are energized.

The inner stator winding 104 and the outer stator winding 112 are selectively energized via a controller 802, such as the controller shown in fig. 8, for example. The controller 802 is coupled to the inner stator winding 104 and the outer stator winding 112. The controller 802 is configured to control the magnitude and direction of current provided to each of the inner stator windings 104, thereby controlling the direction and rotational speed of the inner rotor 106 about the first axis of rotation 116-1, and is also configured to control the magnitude and direction of current provided to the outer stator windings 112, thereby controlling the direction and rotational speed of the outer rotor 114 about the second axis of rotation 116-2. The controller 802 may be configured to implement any of a variety of closed-loop or open-loop control schemes.

The two degree of freedom motor 100 disclosed herein provides several advantages over currently known multiple degree of freedom motors. For example, relatively high torque is generated about the first axis of rotation 116-1 at a lower temperature and higher speed range. Further, rotation about the second rotation axis 116-2 is provided with relatively high precision and linearity.

The two degree of freedom motor 100 shown in fig. 1 and described herein may be used in a UAV, such as UAV 900 shown in fig. 9. The UAV 900 shown therein includes a fuselage 902, a plurality of propellers 904, and a plurality of two-degree-of-freedom motors 100 (only one shown). Each of the propellers 904 is mounted on the fuselage 902 and is rotatable relative to the fuselage 902. Each two-degree-of-freedom motor 100 is also mounted on the fuselage 902, and each two-degree-of-freedom motor is coupled to a different one of the propellers 904. The two degree-of-freedom motor 100 may be controlled via a controller 802 of fig. 8, which may be disposed on the body 902 or separate from the body 902. If provided separately from the housing 902, the controller 802 is configured to wirelessly communicate with a power source that supplies current to the inner and outer stator windings 104, 112. If the controller 802 is disposed on the body 902, a separate user interface device 804 may be used to provide commands to the controller 902, which in turn controls the current to the inner stator winding 104 and the outer stator winding 112.

Those of skill in the art would appreciate that the various illustrative logical blocks, modules, circuits, and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware, computer software, or combinations of both. Some embodiments and implementations are described above in terms of functional and/or logical block components (or modules) and various processing steps. However, it should be appreciated that such block components (or modules) may be realized by any number of hardware, software, and/or firmware components configured to perform the specified functions. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention. For example, an embodiment of a system or component may employ various integrated circuit components, e.g., memory elements, digital signal processing elements, logic elements, look-up tables, or the like, which may carry out a variety of functions under the control of one or more microprocessors or other control devices. In addition, those of skill in the art will appreciate that the embodiments described herein are merely exemplary implementations.

The various illustrative logical blocks, modules, and circuits described in connection with the embodiments disclosed herein may be implemented or performed with the following: a general purpose processor, a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general purpose processor may be a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.

The techniques and technologies may be described herein in terms of functional and/or logical block components and with reference to symbolic representations of operations, processing tasks, and functions that may be performed by various computing components or devices. Such operations, tasks, and functions are sometimes referred to as being computer-executed, computerized, software-implemented, or computer-implemented. In practice, one or more processor devices may perform the operations, tasks, and functions by controlling electrical signals representing data bits at memory locations in system memory, as well as other processed signals. The memory locations where data bits are maintained are physical locations that have particular electrical, magnetic, optical, or organic properties corresponding to the data bits. It should be appreciated that the various block components shown in the figures may be implemented by any number of hardware, software, and/or firmware components configured to perform the specified functions. For example, an embodiment of a system or component may employ various integrated circuit components, e.g., memory elements, digital signal processing elements, logic elements, look-up tables, or the like, which may carry out a variety of functions under the control of one or more microprocessors or other control devices.

When implemented in software or firmware, the various elements of the system described herein are essentially the code segments or instructions that perform the various tasks. The program or code segments can be stored in a processor readable medium or transmitted by a computer data signal embodied in a carrier wave over a transmission medium or communication path. A "computer-readable medium," "processor-readable medium," or "machine-readable medium" may include any medium that can store or transfer information. Examples of a processor-readable medium include electronic circuits, semiconductor memory devices, ROM, flash memory, Erasable ROM (EROM), floppy disks, CD-ROMs, optical disks, hard disks, fiber optic media, Radio Frequency (RF) links, and so forth. The computer data signal may include any signal that can propagate over a transmission medium such as electronic network channels, optical fibers, air, electromagnetic paths, or RF links. The code segments may be downloaded via computer networks such as the internet, intranet, LAN, etc.

Some of the functional units described in this specification have been referred to as "modules," in order to more particularly emphasize their implementation independence. For example, the functions referred to herein as modules may be implemented in whole or in part as hardware circuits comprising custom VLSI circuits or gate arrays, off-the-shelf semiconductors such as logic chips, transistors, or other discrete components. A module may also be implemented in programmable hardware devices such as field programmable gate arrays, programmable array logic, programmable logic devices or the like. Modules may also be implemented in software for execution by various types of processors. An identified module of executable code may, for instance, comprise one or more physical or logical modules of computer instructions which may, for instance, be organized as an object, procedure, or function. Nevertheless, the executables of an identified module need not be physically located together, but may comprise disparate instructions stored in different locations which, when joined logically together, comprise the module and achieve the stated purpose for the module. Indeed, a module of executable code may be a single instruction, or many instructions, and may even be distributed over several different code segments, among different programs, and across several memory devices. Similarly, the operational data may be embodied in any suitable form and may be organized within any suitable type of data structure. The operational data may be collected as a single data set, or may be distributed over different locations including over different storage devices and may exist, at least partially, merely as electronic signals on a system or network.

In this document, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Unless explicitly defined by the claim language, numerical ordinals such as "first", "second", "third", etc., merely denote different individuals in a plurality and do not imply any order or sequence. The sequence of text in any claim does not imply that the process steps must be performed in a temporal or logical order according to such sequence, unless clearly defined by the language of the claim. Method steps may be interchanged in any order without departing from the scope of the invention as long as such an interchange does not contradict the claim language and is not logically nonsensical.

Furthermore, depending on the context, words such as "connected" or "coupled" when used in describing relationships between different elements do not imply that a direct physical connection must be made between the elements. For example, two elements may be connected to each other physically, electronically, logically, or in any other manner, through one or more additional elements.

While at least one exemplary embodiment has been presented in the foregoing detailed description of the invention, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing an exemplary embodiment of the invention. It being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope of the invention as set forth in the appended claims.

Claims (8)

1. A two degree-of-freedom motor, comprising:

an inner stator having a plurality of inner stator poles extending radially outward;

a plurality of inner stator windings wound around the inner stator poles and operable when energized to generate a first magnetic field;

an inner rotor spaced apart from and at least partially surrounding the inner stator, the inner rotor including a plurality of magnets and being mounted for rotation about a first axis of rotation;

an outer stator spaced apart from and at least partially surrounding the inner stator and the inner rotor, the outer stator having a plurality of radially inwardly extending outer stator poles;

a plurality of outer stator windings wound around the outer stator poles and operable when energized to generate a second magnetic field;

an outer rotor spaced apart from and disposed between the inner rotor and the outer stator, the outer rotor having a plurality of radially outwardly extending outer rotor protrusions, the outer rotor mounted for rotation about a second axis of rotation, the second axis of rotation being perpendicular to the first axis of rotation; and

a shaft coupled to the inner rotor and the outer rotor, the shaft selectively rotatable with the inner rotor about the first axis of rotation and selectively rotatable with the outer rotor about the second axis of rotation.

2. The motor of claim 1, further comprising:

a plurality of shaft bearing assemblies, each shaft bearing assembly disposed between the outer rotor and the shaft allowing the shaft to rotate relative to the outer rotor about the first axis of rotation.

3. The motor according to claim 1, wherein:

the outer stator comprises a first predetermined number of outer stator poles;

the outer rotor includes a second predetermined number of outer rotor protrusions; and is

The first predetermined number is greater than the second predetermined number.

4. The motor of claim 1, wherein each of the outer rotor protrusions comprises a ferrous material.

5. The motor of claim 1, wherein each of the outer rotor protrusions includes a permanent magnet.

6. The motor of claim 1, further comprising:

a load coupled to the shaft and rotatable with the shaft about the first and second axes of rotation.

7. The motor of claim 6, wherein the load comprises a propeller.

8. The motor of claim 1, further comprising:

a controller in operable communication with the inner stator winding and the outer stator winding, the controller configured to controllably supply current to the inner stator winding and the outer stator winding.

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