Patent Publication Number: US-2022234749-A1

Title: Systems and methods for driving fan blades of an engine

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application relates to and claims priority benefits from U.S. Provisional Application No. 63/142,527, entitled “Systems and Methods for Driving Fan Blades of an Engine,” filed Jan. 28, 2021, which is hereby incorporated by reference in its entirety. 
    
    
     FIELD OF THE DISCLOSURE 
     Embodiments of the present disclosure generally relate to systems and methods for driving fan blades of an engine, such as an engine of an aircraft. 
     BACKGROUND OF THE DISCLOSURE 
     Various aircraft include propulsion systems, such as two or more engines. For example, certain aircraft include turbofan engines having a plurality of fan blades coupled to an engine core. 
     Existing turbofan engines use gearboxes, additional shafts, or induction motors to drive the fan blades. However, such known driving systems exhibit performance, size, and/or weight drawbacks. Moreover, drive systems that include engine fan motors typically utilize general purpose motors that are configured for ground-based applications, but not aircraft in flight. 
     A known engine includes a gearbox that is used to reduce both a speed and noise of fan blades. The gearbox adds size and weight to the engine, such as by having a relatively large fan at a front end. Another known engine includes a three-spool engine having three shafts, thereby also adding size and weight to the engine. With both of these known engines, a time to spool up an engine typically takes multiple minutes. 
     In order to improve engine performance, independent control of the fan has been proposed. There have been attempts to disengage the fan stage from an engine spool, and drive the fan directly by using an electric motor. 
     For example, an existing induction motor uses conductor bars placed alongside a rotor. The rotor follows a generated rotating electromagnetic field of a stator. However, induction motors are known to have deficiencies in torque and speed control due to an inherent slip. Further, speed adjustment for induction motors is limited. As load increases, rotor speed drops, and slip increases, thereby resulting in an air volume drop that can be unacceptable for any turbofan engine of high bypass ratio (such as greater than 10:1). Additionally, as demand for a surge torque can push the motor beyond a breakdown torque threshold, the induction motor can be susceptible to stalling. 
     On the other hand, conventional permanent magnet motors or brushless direct current (DC) motors, use permanent magnets instead of conductor bars. When stator windings are energized in a rotating manner, the rotor follows the electromagnetic field generated by the stator windings, without slippage. A special driver is typically required for speed and torque control of such motors. 
     For both induction and brushless DC motors, the stators encircle the rotors. Flux generated by each stator winding completes its own loops through the motor housing, resulting in a pattern of multi-dimensional flux flow. As such, core loss, eddy current loss, and the like are high. Both induction and brushless DC motors are bulky and heavy, thereby adding size and weight to an engine. With high torque ripple and poor operation efficiencies, such motors of general purpose are designed for utility and industrial applications on the ground, but are not well suited for turbofan engines of an aircraft. 
     For use on a jet engine, both speed and torque of an electric motor need to be precisely monitored and controlled. A full authority digital engine control (FADEC) is an electronic system including a digital electronic engine controller (EEC), or engine control unit (ECU), and related supporting accessories that control all aspects of aircraft engine performance. However, known FADECs of jetliners typically are not designed for driving an electric motor, let alone provide optimized speed-torque control of such a motor. 
     SUMMARY OF THE DISCLOSURE 
     A need exists for an efficient, compact, and relatively low-weight system and method for driving fan blades of an engine, such as an engine of an aircraft. Further, a need exists for a system and method of driving a motor that drives a fan of an engine. 
     With those needs in mind, certain embodiments of the present disclosure provide a system for driving a fan of an engine of an aircraft. The system includes an electric motor operatively coupled to a drive axle of the fan, and a control unit in communication with the electric motor. The control unit is configured to operate the electric motor to rotate the fan. 
     As an example, the control unit is within the engine. As a further example, the control unit is within the electric motor. 
     In at least one embodiment, the electric motor includes a housing defining an internal chamber, a stator within the internal chamber, and a rotor within the internal chamber. A portion of the drive axle is coupled to the rotor. 
     In at least one embodiment, the rotor extends around the stator. As an example, the rotor includes at least one channel. At least a portion of the stator is disposed within the at least one channel. As an example, the stator includes at least one core disposed between opposed rims of the rotor. 
     The housing can be formed of one or both of an aluminum alloy or a composite material. 
     In at least one example, the rotor includes at least four magnetic poles. 
     As an example, the electric motor further includes an encoder configured to measure rotor flux angles and speed. As a further example, the control unit includes a full authority digital engine control (FADEC) in communication with a speed and torque responder that determines speed and flux angles of the rotor. 
     Certain embodiments of the present disclosure provide a method for driving a fan of an engine of an aircraft. The method includes operatively coupling an electric motor to a drive axle of the fan; communicatively coupling a control unit with the electric motor; and operating, by the control unit, the electric motor to rotate the fan. 
     Certain embodiments of the present disclosure provide an aircraft including an engine having a fan, and a system for driving the fan of the engine, as described herein. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a schematic block diagram of an aircraft having an engine, according to an embodiment of the present disclosure. 
         FIG. 2  illustrates a front perspective view of an aircraft, according to an exemplary embodiment of the present disclosure. 
         FIG. 3  illustrates a lateral perspective view of an engine, according to an embodiment of the present disclosure. 
         FIG. 4  illustrates a transverse cross-sectional view of the engine. 
         FIG. 5  illustrates a simplified transverse internal view of a motor coupled to a drive axle, according to an embodiment of the present disclosure. 
         FIG. 6  illustrates a schematic diagram of a control unit, according to an embodiment of the present disclosure. 
         FIG. 7  illustrates a flow chart of a method for driving a fan of an engine of an aircraft, according to an embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE DISCLOSURE 
     The foregoing summary, as well as the following detailed description of certain embodiments will be better understood when read in conjunction with the appended drawings. As used herein, an element or step recited in the singular and preceded by the word “a” or “an” should be understood as not necessarily excluding the plural of the elements or steps. Further, references to “one embodiment” are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features. Moreover, unless explicitly stated to the contrary, embodiments “comprising” or “having” an element or a plurality of elements having a particular condition may include additional elements not having that condition. 
     Certain embodiments of the present disclosure provide a high-torque engine fan motor for a turbofan engine. Compared to existing systems, the motor has reduced size, weight, and energy loss. Further, an enhanced engine control unit is provided that optimizes speed-torque control for the engine fan motor. 
     Embodiments of the present disclosure allow for precise monitoring and control of speed and torque for an electric motor used to control fan speed in a turbofan engine. In at least one embodiment, the motor is a compact, lightweight electric motor. The motor also has reduced core loss and energy consumption, thereby providing a more efficient system. The motor may also be optimized to permit the speed of fan blade tips to run at higher revolutions per minute, which is beneficial for smaller turbofan engines with smaller-diameter fans. 
     Certain embodiments of the present disclosure provide an electric motor that is configured to provide high-torque and surge torque to a fan of a turbofan engine. The motor allows for reduced flux path to reduce loss. Path loss is further reduced by the ability to use laminated steel for the rotor core and stator core. Less copper is also used, which reduces core loss and energy consumption. With flux not going through the motor housing, materials can be switched from ferrous materials to aluminum alloy or other lighter materials. Optimized motor performance can be achieved by encoders embedded inside the motor. 
       FIG. 1  illustrates a schematic block diagram of an aircraft  100  having an engine  102  (or a front end of a turbofan engine), according to an embodiment of the present disclosure. In at least one embodiment, the engine  102  is a turbofan engine. The engine  102  includes a housing  104  containing a fan  106  coupled to a motor  108 . The fan  106  includes a drive axle  110 . A plurality of fan blades  112  extend radially from a first end  114  of the drive axle  110 . The drive axle  110  also includes a second end  116  that is opposite from the first end  114 . The second end  116  is operatively coupled to the motor  108 . The motor  108  operates to rotate the drive axle  110 , and therefore the fan blades  112 . 
     In at least one embodiment, the motor  108  is an electric motor. A control unit  118  is in communication with the motor  108 , such as through one or more wired or wireless connections. The control unit  118  is configured to operate the motor  108  to drive the fan  106 , as described herein. 
     In at least one embodiment, the control unit  118  is outside of the engine  102 . In at least one other embodiment, the control unit  118  is within the engine  102 , mounted on the motor  108 , or on or within the housing  104 . 
     As described herein, certain embodiments of the present disclosure provide a system  101  for driving the fan  106  of the engine  102  of the aircraft  100 . The system  101  includes the motor  108 , such as an electric motor, operatively coupled to the drive axle  110  of the fan  106 . The control unit  118  is in communication with the electric motor  108 . The control unit  118  is configured to operate the electric motor  108  to rotate the fan  106 . 
     As used herein, the term “control unit,” “central processing unit,” “unit,” “CPU,” “computer,” or the like may include any processor-based or microprocessor-based system including systems using microcontrollers, reduced-instruction set computers (RISC), application-specific integrated circuits (ASICs), logic circuits, and any other circuit or processor including hardware, software, or a combination thereof capable of executing the functions described herein. Such are exemplary only, and are thus not intended to limit in any way the definition and/or meaning of such terms. For example, the control unit  118  may be or include one or more processors that are configured to control operation thereof, as described herein. 
     The control unit  118  is configured to execute a set of instructions that are stored in one or more data storage units or elements (such as one or more memories), in order to process data. For example, the control unit  118  may include or be coupled to one or more memories. The data storage units may also store data or other information as desired or needed. The data storage units may be in the form of an information source or a physical memory element within a processing machine. 
     The set of instructions may include various commands that instruct the control unit  118  as a processing machine to perform specific operations such as the methods and processes of the various embodiments of the subject matter described herein. The set of instructions may be in the form of a software program. The software may be in various forms such as system software or application software. Further, the software may be in the form of a collection of separate programs, a program subset within a larger program or a portion of a program. The software may also include modular programming in the form of object-oriented programming. The processing of input data by the processing machine may be in response to user commands, or in response to results of previous processing, or in response to a request made by another processing machine. 
     The diagrams of embodiments herein may illustrate one or more control or processing units, such as the control unit  118 . It is to be understood that the processing or control units may represent circuits, circuitry, or portions thereof that may be implemented as hardware with associated instructions (e.g., software stored on a tangible and non-transitory computer-readable storage medium, such as a computer hard drive, ROM, RAM, or the like) that perform the operations described herein. The hardware may include state machine circuitry hardwired to perform the functions described herein. Optionally, the hardware may include electronic circuits that include and/or are connected to one or more logic-based devices, such as microprocessors, processors, controllers, or the like. Optionally, the control unit  118  may represent processing circuitry such as one or more of a field-programmable gate array (FPGA), application-specific integrated circuit (ASIC), microprocessor(s), and/or the like. The circuits in various embodiments may be configured to execute one or more algorithms to perform functions described herein. The one or more algorithms may include aspects of embodiments disclosed herein, whether or not expressly identified in a flowchart or a method. 
     As used herein, the terms “software” and “firmware” are interchangeable, and include any computer program stored in a data storage unit (for example, one or more memories) for execution by a computer, including RAM memory, ROM memory, EPROM memory, EEPROM memory, and non-volatile RAM (NVRAM) memory. The above data storage unit types are exemplary only, and are thus not limiting as to the types of memory usable for storage of a computer program. 
       FIG. 2  illustrates a front perspective view of the aircraft  100 , according to an exemplary embodiment of the present disclosure. The aircraft  100  includes a propulsion system  212  that includes two engines  102 , for example. Optionally, the propulsion system  212  may include more engines  102  than shown. The engines  102  are carried by wings  216  of the aircraft  100 . In other embodiments, the engines  102  are carried by a fuselage  218  and/or an empennage  220 . The empennage  220  may also support horizontal stabilizers  222  and a vertical stabilizer  224 . The fuselage  218  of the aircraft  100  defines an internal cabin, including a flight deck. 
       FIG. 3  illustrates a lateral perspective view of an engine  102 , according to an embodiment of the present disclosure. In at least one embodiment, the engine  102  is a turbofan engine having a case  300  that includes an engine inlet  314 . The engine inlet  314  may include a leading edge  316  and an inner barrel section  320  located aft of the leading edge  316  of the engine inlet  314 . The inner barrel section  320  may provide a boundary surface or wall for directing airflow (not shown) entering the engine inlet  314  and passing through the engine  102 . The inner barrel section  320  may be located in relatively close proximity to one or more fan blades (not shown in  FIG. 3 ). In this regard, the inner barrel section  320  may also be configured to serve as an acoustic structure having a plurality of perforations in an inner face sheet of the inner barrel section  320  for absorbing noise generated by the rotating fan blades and/or noise generated by the airflow entering the engine inlet  314  and passing through the engine  102 . 
       FIG. 4  illustrates a transverse cross-sectional view of an engine  102 , such as a turbofan engine. The fan blades  112  of the fan  106  are located at a fore end of the engine  102  proximate to the engine inlet  314  that receives airflow  400 . The engine  102  further includes a low pressure compressor  402  and a high pressure compressor  403 . The fan blades  112  may be decoupled (for example, detached) from the low pressure compressor  402 . The motor  108  and the control unit  118  may be disposed between the fan blades  112  and the low pressure compressor  402 . In at least one embodiment, the drive axle  110  includes a low pressure shaft  404  coaxial with, and inside of, a high pressure shaft  406 . Optionally, the drive axle  110  can be or otherwise include a single shaft. A high pressure turbine  408  is behind (for example, downstream from) the high pressure compressor  403 . A low pressure turbine  410  is behind (for example, downstream from) the high pressure turbine  408 . A nozzle  412  is at or otherwise proximate to an outlet end  414 . 
     The low pressure shaft  404  and the high pressure shaft  406  operate separately on two engine spools, for example. N1 reading on a cockpit display commonly refers to the speed of the spool on which the fan blades  112  (such as the low pressure compressor  402  and the low pressure turbine  410  stages) are attached. N2 on the cockpit display commonly represents the spool of the high pressure compressor  403  in the compressor core and the high pressure turbine  408  in the gas core. 
     In order to draw in sufficient airflow  400 , while at the same time reducing the noise generated by the moving air, the tip speed (that is, the speed of the outermost portions) of the fan blades  112  is controlled, such as via the control unit  118  operating the motor  108  (shown in  FIG. 1 ). If the tip speed was not controlled, the resulting energy could be used to suppress supersonic shockwaves, resulting in poor fuel efficiency of the engine  102 . 
     As noted above, a known engine includes a gearbox to reduce both the speed and the noise of the fan blades. However, the gearbox adds size and weight to the engine. Another known engine includes an additional shaft, thereby providing a three-spool engine. Such known engines typically exhibit engine spool-up times of multiple minutes. The fan speed is determined by the speed of one spool, with or without a gear ratio. 
       FIG. 5  illustrates a simplified transverse internal view of the motor  108  coupled to the drive axle  110 , according to an embodiment of the present disclosure. The motor  108  includes a housing  500  that receives the second end  116  of the drive axle  110 . The second end  116  of the drive axle  110  passes through a passage  502  of the housing  500 . The motor  108  is configured to rotate the drive axle  110 , such as in the direction of arc A. 
     The housing  500  defines an internal chamber  501  that contains a rotor  504  and a stator  506 . That is, the rotor  504  and the stator  506  are within the internal chamber  501 . The second end  116  of the drive axle  110  passes through the rotor  504 . 
     In contrast to known motors, the rotor  504  extends around the stator  506  including windings  507 . For example, the rotor  504  includes at least one channel  508 . In at least one embodiment, an inboard portion  510  of the rotor  504  is disposed between the stator  506  and the drive axle  110 . In at least one embodiment, the rotor  504  directly connects to the drive axle  110 . 
     In at least one embodiment, the rotor  504  includes at least portions that are outside of the stator  506 . For example, the stator  506  is disposed within the channel(s)  508 . The stator  506  includes at least portions that are not outboard (that is, not further away from a central axis  514 ) from at least portions of the rotor  504 . 
     In at least one embodiment, the rotor  504  encircles the stator  506 . The stator  506  can be disposed within the rotor  504 , such as within the channel  508 . 
     In at least one embodiment, the stator  506  includes a plurality of cores  512 . For example, the stator  506  can include two, three, four, or more cores  512  regularly spaced about a central axis  514  of the motor  108 . Each core  512  is sandwiched between opposed rims  520  of the rotor  504  within a channel  508 . The rims  520  are connected together through the inboard portion  510 , which is inboard (that is, closer to the central axis  514 ) than the stator  506 . As such, the rims  520  and inboard portion  510  of the rotor  504  forms a U shaped structure, in which the cores  512  of the stator  506  are disposed within the channel(s)  508 . 
     Because flux is routed to the path of least reluctance, the flux does not pass through the housing  500 . A length of each flux path is therefore much shorter (as compared to motors in which stators encircle a rotor), thereby resulting in less loss in each path. Accordingly, the flux is localized in unidirectional flow. In at least one embodiment, due to unidirectional flow of flux, the rotor  504  and/or the stator  506  can be formed of grain-oriented steel in a laminated form to further reduce the path loss. 
     Additionally, the windings  507  of the stator  506  include less copper (as compared to known stators), thereby reducing weight and cost. By reducing the core loss and energy consumed by the windings  507 , overall efficiency of the motor  108  is improved over conventional motors. Moreover, internal shaft-mounted cooling fans and heat sinks on the housing  500  are no longer needed. Because flux does not pass through the housing  500 , the housing can be made with a lightweight material, such as an aluminum alloy, a composite material, or the like, instead of heavy iron or other ferrous materials. 
     Moreover, by having at least two magnetic poles  520  (in at least one embodiment, at least four magnetic poles  520 , as shown in  FIG. 5 ) placed around the rotor  504 , extra torque with reduced torque ripple is available within a given space. Motor torque and efficiency are improved, while motor size and weight are reduced. In at least one embodiment, for motor performance optimization, an encoder  540  made of magnets and sensors can be embedded inside the motor  108  to measure the rotor flux angles and speed of the rotor in revolutions per minute (RPM). The motor  108  permits the speed of fan blade tips to run at higher RPM. As such, the motor  108  is well-equipped for use in smaller turbofan engines, such as on wings where ground clearance is limited. 
     As described herein, the motor  108  is operated by the control unit  118  (shown in  FIG. 1 ). The control unit  118  can be externally mounted on the housing  500 . A wide range of speed-torque control, even a surge of torque demand during airplane takeoff and/or emergency go-around at landing, can be accomplished with an enhancement to a FADEC engine controller. 
       FIG. 6  illustrates a schematic diagram of the control unit  118 , according to an embodiment of the present disclosure. Referring to  FIGS. 5 and 6 , in at least one embodiment, the control unit  118  provides a FADEC enhancement (for example, an enhanced FADEC) that incorporates a speed and torque responder  600 , which is well suited for a compact motor capable of providing high torque. For example, in at least one embodiment, the control unit  118  is or otherwise includes a FADEC in communication with a speed and torque responder  600 . In at least one embodiment, the motor  108  includes the embedded encoder  540  that provides RPM signals as well as flux angles of the rotor  504 . The speed and torque responder  600  is in communication with the encoder  540 . The speed and torque responder  600  determines the speed and the flux angles of the rotor  504 , such as through signals received from the encoder  540 . 
     To obtain maximum motor torque at a given motor current, vector orientation of the stator current can be at 90° with respect to the rotor flux. The encoder  540  embedded inside the motor  108  counts the RPM and measures the rotor flux angle. The speed and torque responder  600  of the control unit  118  receives signals from the encoder  540  as well as the commands for change of speed and/or torque. The speed and torque responder  600  provides signals for desired speed and desired torque, as well as direct current which can be nulled. 
     A vector controller  602  calculates the amplitude and phase values of the motor current each at 90° with respect to the rotor flux, then creates three current vectors or signals. First, a Clarke transformation takes any two out of the three signals of the motor current, adds the two, then negates the sum to obtain the third, thus converting three 120°-phase-apart vectors into two phase vectors α and β in 90° coordinates. Next, a Park transformation rotates these new α-β coordinates where quadrature axis lines up 90° with respect to direct axis, that is, the rotor flux. Sinusoidal moving values of the motor currents are Park transformed into slow varying (substantially DC) values in D-axis and Q-axis, meanwhile AC frequency becomes absent. Q-axis has the torque command of the motor while commanded D-axis value (undesirable D-torque) is minimized or otherwise reduced. The speed and torque responder  600  produces two error signals εq and εd. Pi filters made from capacitors and inductors produce Vq and Vd. Using inverse Park transformation, stationary reference is transformed back to α-β rotational reference. Finally, inverse Clarke transformation returns three voltage signals to modulate the power drive stage and energize the windings  507  of the stator  506 . The speed of the rotor  504  in RPM is obtained from the encoder  540 . The measured RPM signal is filtered and compared with a received speed command. An error signal es is produced and processed by the speed and torque responder  600 , before desired torque and nulled direct current are computed. In general, the control unit  118  can be or otherwise include a speed-torque vector controller containing two feedback loops: a torque loop inside of a speed loop. The process repeats itself every time the control unit  118  receives a command signal via a data bus for a change of speed and torque for the fan motor. 
     Referring to  FIGS. 1-6 , the control unit  118  can be remote from the engine  102 . In at least one other embodiment, the control unit  118  can be disposed within the engine  102 , such as within the housing  104 . As a further example, the motor  108  can include the control unit  118 . For example, as shown in  FIG. 5 , the control unit  118  can be embedded or otherwise housed within the motor  108 . As described herein a high torque motor and an enhanced engine controller is provides optimum engine operations under any flight condition. 
       FIG. 7  illustrates a method for driving a fan of an engine of an aircraft, according to an embodiment of the present disclosure. The method comprises operatively coupling, at  700 , an electric motor to a drive axle of the fan; communicatively coupling, at  702 , a control unit with the electric motor; and operating at  704 , by the control unit, the electric motor to rotate the fan. 
     In at least one embodiment, the method also includes disposing a stator within an internal chamber of a housing of the electric motor; disposing a rotor within the internal chamber; and coupling a portion of the drive axle to the rotor. 
     As an example, the method also includes extending the rotor around the stator. Also, as an example, the method includes disposing at least a portion of the stator within at least one channel of the rotor. As a further example, the method includes disposing at least one core of the stator between opposed rims of the rotor. 
     In at least one embodiment, the method includes providing the rotor with at least four magnetic poles. 
     In at least one embodiment, the method includes measuring, by an encoder of the electric motor, rotor flux angles and speed. 
     As an example, the method also includes communicatively coupling a full authority digital engine control (FADEC) of the control unit with a speed and torque responder; and determining, by the speed and torque responder, speed and flux angles of the rotor. 
     As described herein, embodiments of the present disclosure provide efficient, compact, and relatively low-weight systems and methods for driving fan blades of an engine, such as an engine of an aircraft. 
     Further, the disclosure comprises embodiments according to the following clauses: 
     Clause 1. A system for driving a fan of an engine of an aircraft, the system comprising: 
     an electric motor operatively coupled to a drive axle of the fan; and 
     a control unit in communication with the electric motor, 
     wherein the control unit is configured to operate the electric motor to rotate the fan. 
     Clause 2. The system of Clause 1, wherein the control unit is within the engine. 
     Clause 3. The system of Clause 1, wherein the control unit is within the electric motor. 
     Clause 4. The system of any of Clauses 1-3, wherein the electric motor comprises: 
     a housing defining an internal chamber; 
     a stator within the internal chamber; and 
     a rotor within the internal chamber, 
     wherein a portion of the drive axle is coupled to the rotor. 
     Clause 5. The system of Clause 4, wherein the rotor extends around the stator. 
     Clause 6. The system of Clauses 4 or 5, wherein the rotor comprises at least one channel, and wherein at least a portion of the stator is disposed within the at least one channel. 
     Clause 7. The system of any of Clauses 4-6, wherein the stator comprises at least one core disposed between opposed rims of the rotor. 
     Clause 8. The system of any of clauses 4-7, wherein the housing is formed of one or both of an aluminum alloy or a composite material. 
     Clause 9. The system of any of Clauses 4-8, wherein the rotor comprises at least four magnetic poles. 
     Clause 10. The system of any of Clauses 4-9, wherein the electric motor further comprises an encoder configured to measure rotor flux angles and speed. 
     Clause 11. The system of any of clauses 4-10, wherein the control unit comprises a full authority digital engine control (FADEC) in communication with a speed and torque responder that determines speed and flux angles of the rotor. 
     Clause 12. A method for driving a fan of an engine of an aircraft, the method comprising: 
     operatively coupling an electric motor to a drive axle of the fan; 
     communicatively coupling a control unit with the electric motor; and 
     operating, by the control unit, the electric motor to rotate the fan. 
     Clause 13. The method of Clause 12, wherein a stator is within an internal chamber of a housing of the electric motor, wherein a rotor is within the internal chamber, and wherein the method further comprises coupling a portion of the drive axle to the rotor. 
     Clause 14. The method of Clause 13, wherein the rotor extends around the stator. 
     Clause 15. The method of Clauses 13 or 14, wherein at least a portion of the stator is within at least one channel of the rotor. 
     Clause 16. The method of any of Clauses 13-15, wherein at least one core of the stator is between opposed rims of the rotor. 
     Clause 17. The method of any of Clauses 13-16, wherein the rotor comprises at least four magnetic poles. 
     Clause 18. The method of any of Clauses 13-17, further comprising measuring, by an encoder of the electric motor, rotor flux angles and speed. 
     Clause 19. The method of any of Clauses 13-18, further comprising: 
     communicatively coupling a full authority digital engine control (FADEC) of the control unit with a speed and torque responder; and 
     determining, by the speed and torque responder, speed and flux angles of the rotor. 
     Clause 20. An aircraft comprising: 
     an engine having a fan; and 
     a system for driving the fan of the engine, the system comprising: 
     an electric motor operatively coupled to a drive axle of the fan, wherein the electric motor comprises a housing defining an internal chamber, a stator within the internal chamber, a rotor within the internal chamber, and an encoder configured to measure rotor flux angles and speed, wherein a portion of the drive axle is coupled to the rotor, wherein the rotor comprises at least one channel, wherein at least a portion of the stator is disposed within the at least one channel; and 
     a control unit in communication with the electric motor, 
     wherein the control unit is configured to operate the electric motor to rotate the fan, wherein the control unit comprises a full authority digital engine control (FADEC) in communication with a speed and torque responder that determines speed and flux angles of the rotor. 
     While various spatial and directional terms, such as top, bottom, lower, mid, lateral, horizontal, vertical, front and the like may be used to describe embodiments of the present disclosure, it is understood that such terms are merely used with respect to the orientations shown in the drawings. The orientations may be inverted, rotated, or otherwise changed, such that an upper portion is a lower portion, and vice versa, horizontal becomes vertical, and the like. 
     As used herein, a structure, limitation, or element that is “configured to” perform a task or operation is particularly structurally formed, constructed, or adapted in a manner corresponding to the task or operation. For purposes of clarity and the avoidance of doubt, an object that is merely capable of being modified to perform the task or operation is not “configured to” perform the task or operation as used herein. 
     It is to be understood that the above description is intended to be illustrative, and not restrictive. For example, the above-described embodiments (and/or aspects thereof) may be used in combination with each other. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the various embodiments of the disclosure without departing from their scope. While the dimensions and types of materials described herein are intended to define the parameters of the various embodiments of the disclosure, the embodiments are by no means limiting and are exemplary embodiments. Many other embodiments will be apparent to those of skill in the art upon reviewing the above description. The scope of the various embodiments of the disclosure should, therefore, be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. In the appended claims, the terms “including” and “in which” are used as the plain-English equivalents of the respective terms “comprising” and “wherein.” Moreover, the terms “first,” “second,” and “third,” etc. are used merely as labels, and are not intended to impose numerical requirements on their objects. Further, the limitations of the following claims are not written in means-plus-function format and are not intended to be interpreted based on 35 U.S.C. § 112(f), unless and until such claim limitations expressly use the phrase “means for” followed by a statement of function void of further structure. 
     This written description uses examples to disclose the various embodiments of the disclosure, including the best mode, and also to enable any person skilled in the art to practice the various embodiments of the disclosure, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the various embodiments of the disclosure is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if the examples have structural elements that do not differ from the literal language of the claims, or if the examples include equivalent structural elements with insubstantial differences from the literal language of the claims.