Patent Application
20210234448
The present application claims benefit of prior filed Indian Provisional Patent Application No. 202011003534, filed Jan. 27, 2020, which is hereby incorporated by reference herein in its entirety.
The present invention generally relates to multi degree-of-freedom motors, and more particularly relates to two degree-of-freedom high tilt torque motors, systems, and aerial vehicles that incorporate the same.
Recent developments in the field of UAV (Unmanned Aerial Vehicles), drones for unmanned air transport, robotics, office automation, and intelligent flexible manufacturing and assembly systems have necessitated the development of precision actuation systems with multiple degrees of freedom (DOF). Conventionally, applications that rely on multiple (DOF) motion have typically done so by using a separate motor/actuator for each axis, which results in complicated transmission systems and relatively heavy structures.
With the advent of spherical motors, there have been multiple attempts to replace the complicated multi-DOF assembly with a single spherical motor assembly. A typical spherical motor consists of a central sphere on which coils are wound, which may be orthogonally placed from each other. The sphere is surrounded by multi-pole magnets in the form of an open cylinder. The coil assembly is held axially and maintained in a vertical position via, for example, a metal post. The outer cylinder is held by a yoke/frame via a bearing, which allows the cylinder to be rotatable about its axis. The yoke is further connected to the metal post of the coil assembly via a second bearing, which allows the yoke, along with the cylinder, to be rotatable about one or two additional axes.
Unfortunately, current attempts to apply the spherical motor to the certain applications, such as UAVs and robotics, have led to several spherical motor design concepts. Unfortunately, many of these design concepts suffer certain drawbacks. For example, many exhibit relatively limited torque and precise positioning, especially in the tilt axis. This is due, at least in part, to a relatively large air gap between the magnets and inner spherical stator (due in part to the windings) and a relatively heavy spherical stator. The current concepts also exhibit relatively high winding temperatures, relatively complicated and time-consuming winding patterns,
Hence, there is a need for a multi-degree-of-freedom electromagnetic machine that at least exhibits improved generated torque and position precision—especially in the tilt axis, improved thermal handling capabilities, improved speed range, and simpler coil winding configurations as compared to presently known spherical motors. The present invention addresses at least this need.
This summary is provided to describe select concepts in a simplified form that are further described 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 determining the scope of the claimed subject matter.
In one embodiment, a two degree-of-freedom motor includes a stator, a plurality of stator windings, a rotor, a shaft, a limited angle torque motor, and a spring. The stator has a main body and a plurality of stator poles extending radially outwardly from the main body. The stator windings are wound around the stator poles and are operable, upon being energized, to generate a magnetic field. The rotor is spaced apart from the stator and includes a plurality of magnets and is configured to rotate about a first rotational axis. The shaft is coupled to the rotor and is rotatable therewith about the first rotational axis. The shaft extends through the stator and has a shaft first end and a shaft second end. The limited angle torque motor is coupled to the shaft first end, and is operable, upon being energized, to supply a torque to the shaft that causes the shaft, the rotor, and the stator to rotate about a second rotational axis that is perpendicular to the first rotational axis. The spring is fixedly mounted and is coupled to the limited angle torque motor.
In another embodiment, a two degree-of-freedom motor system includes a stator, a plurality of stator windings, a rotor, a shaft, a limited angle torque motor, a spring, and a control. The stator has a main body and a plurality of stator poles extending radially outwardly from the main body. The stator windings are wound around the stator poles and are operable, upon being energized, to generate a magnetic field. The rotor is spaced apart from the stator, and includes a plurality of magnets and is configured to rotate about a first rotational axis. The shaft is coupled to the rotor and is rotatable therewith about the first rotational axis. The shaft extends through the stator and has a shaft first end and a shaft second end. The limited angle torque motor is coupled to the shaft first end, and is operable, upon being energized, to supply a torque to the shaft that causes the shaft, the rotor, and the stator to rotate about a second rotational axis that is perpendicular to the first rotational axis. The spring is fixedly mounted and is coupled to the limited angle torque motor. The control is in operable communication with the stator windings and the limited angle torque motor, and is configured to controllably supply current to the stator windings and the limited angle torque motor.
In yet another embodiment, an unmanned aerial vehicle (UAV) includes an airframe, a plurality of propellers, and a plurality of two degree-of-freedom motors. The propellers are rotatable relative to the airframe and the two degree-of-freedom motors are mounted on the airframe. Each two degree-of-freedom motor is coupled to a different one of the propellers, and each includes a stator, a plurality of stator windings, a rotor, a shaft, a limited angle torque motor, and a spring. The stator has a main body and a plurality of stator poles extending radially outwardly from the main body. The stator windings are wound around the stator poles and are operable, upon being energized, to generate a magnetic field. The rotor is spaced apart from the stator, and includes a plurality of magnets and is configured to rotate about a first rotational axis. The shaft is coupled to the rotor and is rotatable therewith about the first rotational axis. The shaft extends through the stator and has a shaft first end and a shaft second end. The shaft second end is coupled to one of the propellers. The limited angle torque motor is coupled to the shaft first end, and is operable, upon being energized, to supply a torque to the shaft that causes the shaft, the rotor, and the stator to rotate about a second rotational axis that is perpendicular to the first rotational axis. The spring is fixedly mounted and is coupled to the limited angle torque motor.
Furthermore, other desirable features and characteristics of the two degree-of-freedom motor, system, and aerial vehicle will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the preceding background.
The present invention will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements, and wherein:
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
Regardless of the number of stator poles 204 and stator slots 206, the stator windings 104 are wound around the stator poles 204 and extend through the stator slots 206. The stator windings 104 may be wound in either concentrated or distributed fashion within these slots 206. In the depicted embodiment, it is noted that the stator windings 104 are implemented as 3-phase windings. In other embodiments, however, the distributed stator windings 104 may be implemented with N-number of phases, where N is an integer greater than or less than three. Regardless of the number phases, the stator windings 104 are operable, upon being energized, to generate a magnetic field.
With continued reference to
It is noted that the depicted embodiments (
Returning now to
The limited angle torque motor 110, as was noted above, is coupled to the shaft first end 116. The limited angle torque motor 100 is configured to selectively supply a torque to the shaft 108. More specifically, the limited angle torque motor 110 is operable, upon being electrically energized, to supply a torque to the shaft 108 that, because the shaft 108 is coupled to the rotor 106, causes the shaft 108 and the rotor 106 to rotate. In particular, it causes the shaft 108 and rotor 106 to rotate about a second rotational axis 114-2 that is perpendicular to the first rotational axis 114-1. One embodiment of the limited angle torque motor 110 is depicted more clearly in
The depicted limited angle torque motor 110 includes a housing 302, a plurality of pole pieces 304 (shown most clearly in
The armature 308 is rotationally mounted within the housing cavity 316 to rotate, at a pivot 322, about the second rotational axis 114-2. The armature 308 includes an armature first end 324 and an armature second end 326. The armature first end 324 is disposed within the housing cavity 316 and is coupled to a spring 320. The armature second end 326 extends from the housing cavity 316 and is coupled to the shaft 108. As noted above, a first portion 328 of the armature 308 extends into and through the armature opening 318 and is thus at least partially surrounded by the pole pieces 304 and permanent magnets 306. A second portion of the armature 332 is surrounded by the actuation coil 308, which is disposed adjacent to the plurality of poles 304 and to the plurality of permanent magnets 306 and is adapted to receive a control current.
The spring 320 is fixedly mounted and is coupled to the limited angle torque motor 110. In the depicted embodiment, the spring 320 is fixedly mounted to the housing 302 within the housing cavity 316 and is coupled to the armature 308. Although the spring 320 may be variously implemented, in the depicted embodiment it is implemented as a tubular spring that surrounds the armature first end 324.
With the configuration described herein, when the stator windings 104 are energized, the generated magnetic field causes the rotor 106 (and thus the shaft 108) to rotate about the first rotational axis 114-1. As noted above, a load 122, such as the depicted propeller, may be coupled to the shaft 108 to receive the torque supplied therefrom. More specifically, when the stator windings 104 are energized with alternating current (AC) voltages, a Lorentz force is generated between the stator windings 104 and the magnets 214, which in turn imparts a torque to the rotor 106 (and thus the shaft 108) that causes it to rotate about the first rotational axis 114-1 (e.g., spin axis).
Moreover, when the actuation coil 312 in the limited angle torque motor 110 is energized, it will cause the armature 308, and thus the rotor 106 and shaft 108, to rotate about the second rotational axes 114-2. More specifically, when the actuation coil 408 is energized with a DC voltage, the actuation coil 312 generates a magnetic flux generated that adds to the magnetic flux of the permanent magnets on one side of the air gap and subtracts from the flux of permanent magnets on the other side. This generates a torque on the armature 308, causing it to rotate about the second rotational axis 114-2. The magnitude and direction of the torque depends on the magnitude and direction of the input current supplied to the actuation coil 312.
The stator windings 104 and actuation coil 312 are selectively energized via, for example, a controller 502, such as the one depicted in
The two degree-of-freedom motor 100 disclosed herein provides several advantages over presently known multi-degree-of-freedom motors. For example, it generates relatively higher torque about the first rotational axis 114-1, at lower temperatures and a higher speed range. In addition, the rotation about the second rotational axis 114-2 is provided at a relatively higher precision and linearity with closed loop current control of current to the limited angle torque motor 110. This can be seen in
The torque generated about the second rotational axis 114-2 by the limited angle torque motor 110 can be even further improved by varying the shape of the first portion 328 of the armature 308, and by varying the shapes of those portions of the pole pieces 304 and the permanent magnets 306 that define the armature opening 318, such that the first portion 328 of the armature 308 and the armature opening 318 each have a polygonal cross-sectional shape. Some example polygonal cross-sectional shapes for the first portion 328 of the armature 308 and the armature opening 318 are depicted in
For completeness, the torque vs. current characteristics for the limited angle torque motor 110 implemented with each of the polygonal cross-sectional shapes and the conventional cross-sectional shapes are graphically depicted in
In addition to (or instead of) varying the cross-sectional shapes of the first portion 328 of the armature 308 and the armature opening 318, a portion of the armature pole pieces 304 and the first portion 328 of the armature 308 can be manufactured to have a plurality of grooves formed therein. As
The two degree-of-freedom motor 100 depicted in
Those of skill in the art will 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 of the 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 a 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 skilled in the art will appreciate that 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 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.
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 can carry out the described operations, tasks, and functions by manipulating electrical signals representing data bits at memory locations in the system memory, as well as other processing of 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 realized by any number of hardware, software, and/or firmware components configured to perform the specified functions. For example, an embodiment of a system or a 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, various elements of the systems 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. The “computer-readable medium”, “processor-readable medium”, or “machine-readable medium” may include any medium that can store or transfer information. Examples of the processor-readable medium include an electronic circuit, a semiconductor memory device, a ROM, a flash memory, an erasable ROM (EROM), a floppy diskette, a CD-ROM, an optical disk, a hard disk, a fiber optic medium, a radio frequency (RF) link, or the like. 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, an intranet, a LAN, or the like.
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, functionality referred to herein as a module may be implemented wholly, or partially, as a hardware circuit 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 that 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 that, 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, operational data may be embodied in any suitable form and 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. Numerical ordinals such as “first,” “second,” “third,” etc. simply denote different singles of a plurality and do not imply any order or sequence unless specifically defined by the claim language. The sequence of the text in any of the claims does not imply that process steps must be performed in a temporal or logical order according to such sequence unless it is specifically defined by the language of the claim. The process 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 “connect” or “coupled to” used in describing a relationship between different elements do not imply that a direct physical connection must be made between these 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.
| Number | Date | Country | Kind |
|---|---|---|---|
| 202011003534 | Jan 2020 | IN | national |
