Motor driven propulsor of an aircraft

A motor driven propulsor of an aircraft includes magnets disposed in fan shrouds of fan blades connected with a fan hub, a stator having individual conductive coils in a nacelle located radially outside of the fan hub, and a distributed inverter assembly having several inverter power stages and gate drivers, each of the inverter power stages coupled with a separate gate driver of the gate drivers and a separate coil of the coils in the stator. Each of the gate drivers is configured to individually control supply of direct current to the corresponding inverter power stage. Each of the inverter power stages is configured to convert the direct current supplied to the inverter power stage to an alternating current that is supplied to the corresponding coil in the stator to rotate the magnets and the fan blades around a center line of the fan hub for propelling the aircraft.

FIELD

The subject matter described herein relates to propulsion systems of aircraft.

BACKGROUND

A traditional aircraft propulsor includes a gas turbine engine located at or within a fan hub of the propulsor. The gas turbine engine consumes fuel to rotate fan blades within a nacelle of the propulsor. This rotation of the fan blades generates thrust to propel the aircraft.

These types of propulsors suffer from several shortcomings. The equipment needed to convert rotation of the turbine engine into rotation of the fan blades can require separate gearboxes, bearings, cooling systems, and the like, all of which undesirably add to the weight of the aircraft. Additionally, gas turbine engines generate significant acoustic noise during operation, which can be undesirable to passengers of the aircraft.

Some proposed aircraft propulsors may include an electric motor to assist with rotation of the fan blades. These motors can help propel the aircraft after the gas turbine engine has provided significant thrust during takeoff or lift off of the aircraft. But, some of these proposed motors may not generate enough power for the thrust needed for takeoff or lift off of the aircraft. Additionally, some of these motors can generate significant heat that may require separate cooling systems to maintain in an operative state. Moreover, the motors may not be able to operate on their own and without associated gas turbine engines due to the motors being less reliable than the gas turbine engines. For example, an inverter that supplies current to the coils of the motor may fail, which prevents the motor from continuing to operate. Such a motor requires an additional propulsor (e.g., the associated gas turbine engine) to prevent catastrophic failure of the aircraft.

BRIEF DESCRIPTION

In one embodiment, a motor driven propulsor of an aircraft is provided. The propulsor includes magnets disposed in fan shrouds of fan blades connected with a fan hub, a stator having individual conductive coils in a nacelle located radially outside of the fan hub, and a distributed inverter assembly having several inverter power stages and gate drivers, each of the inverter power stages coupled with a separate gate driver of the gate drivers and a separate coil of the coils in the stator. Each of the gate drivers is configured to individually control supply of direct current to the corresponding inverter power stage. Each of the inverter power stages is configured to convert the direct current supplied to the inverter power stage to an alternating current that is supplied to the corresponding coil in the stator to rotate the magnets and the fan blades around a center line of the fan hub for propelling the aircraft.

In one embodiment, a method for providing a motor driven propulsor of an aircraft is provided. The method includes placing magnets disposed in fan shrouds of fan blades connected with a fan hub, positioning a stator having individual conductive coils in a nacelle located radially outside of the fan hub, and coupling several inverter power stages of a distributed inverter assembly with several gate drivers. Each of the inverter power stages is coupled with a separate gate driver of the gate drivers. The method also includes conductively coupling each of the inverter power stages with a different coil of the coils in the stator. Each of the gate drivers is coupled with a different inverter power stage of the inverter power stages to individually control supply of direct current to the corresponding inverter power stage. Each of the inverter power stages is coupled with the corresponding gate driver and the corresponding coil to convert the direct current supplied to the inverter power stage to an alternating current that is supplied to the corresponding coil in the stator to rotate the magnets and the fan blades around a center line of the fan hub for propelling the aircraft.

In one embodiment, a motor driven propulsor includes magnets disposed in fan shrouds of fan blades connected with a fan hub, a stator having individual conductive coils in a nacelle located radially outside of the fan hub, and a distributed inverter assembly having several inverter power stages. Each of the inverter power stages is close coupled with a separate coil of the coils in the stator. Each of the inverter power stages is configured to power the corresponding coil in the stator to rotate the magnets and the fan blades around a center line of the fan hub for generating a propulsive force. The inverter power stages are separately coupled with the coils in the stator such that one or more inverter power stages continue powering the corresponding coils to continue generating the propulsive force after failure of at least one of the inverter power stages.

DETAILED DESCRIPTION

Embodiments of the subject matter described herein relate to motor driven propulsors of aircraft. In one embodiment, a fan of a turbofan engine is combined with an electric motor (also referred to as a generator). The fan can be combined with the motor without also connecting the turbofan or a turbine engine with the fan (or any other fan of the same aircraft, in one example). The electrical motor is located on outside of the fan in a nacelle of the aircraft. A shrouded fan is provided with permanent magnets embedded in the shroud of fan blades of the fan. The stator of the motor is provided in the nacelle. A close coupled distributed inverter can be provided to provide alternating current (AC) power to coils of the stator (that are in the nacelle). This distributed inverter also can be in the nacelle. The external and internal surfaces of the nacelle may be used to dissipate heat of the electric motor to air flowing inside and outside the nacelle to assist with cooling and rejecting heat from the motor and associated components. One or more gate drivers are provided to individually control power stages of the distributed inverter using a high-speed communication channel, such as via optical fibers, in one embodiment. A direct current (DC) power bus can be provided around the nacelle to provide power to the distributed power stages of the inverter.

By placing the electrical motor directly on the shroud of the fan, significant savings of weight are achieved relative to turbofan propulsors, as the need for separate or additional gearboxes, bearings, cooling systems, and housings are eliminated. Significant weight savings can be achieved by utilizing the motor at the highest shear gap velocities obtainable by the motor. Use of an electric motor instead of a turbofan also significantly reduces the acoustic noise generated by operation of the propulsor.

While one or more embodiments described herein provide the stator and stator coils radially outward of a hub to which the fan blades of the propulsor are connected (e.g., relative to an axis of rotation or center line of the hub of the propulsor), alternatively, the stator and coils can be placed inside the hub to rotate the fan blades.

FIG. 1provides a top view of an aircraft10as may incorporate various embodiments of the inventive subject matter described herein. The aircraft10defines a longitudinal centerline14that extends therethrough, a lateral direction L, a forward end16, and an aft end18. The aircraft10includes a fuselage12that longitudinally extends from the forward end16of the aircraft10to the aft end18of the aircraft10, and a wing assembly including a port side and a starboard side. The port side of the wing assembly is a first, port side wing20, and the starboard side of the wing assembly is a second, starboard side wing22. The first and second wings20,22each extend laterally outward with respect to the longitudinal centerline14. The first wing20and a portion of the fuselage12together define a first side24of the aircraft10, and the second wing22and another portion of the fuselage12together define a second side26of the aircraft10. In the illustrated embodiment, the first side24of the aircraft10can be referred to as the port side of the aircraft10, and the second side26of the aircraft10can be referred to as the starboard side of the aircraft10.

Each of the wings20,22includes one or more leading edge flaps28and one or more trailing edge flaps30. The aircraft10further includes a vertical stabilizer32having a rudder flap (not shown) for yaw control, and a pair of horizontal stabilizers34, each having an elevator flap36for pitch control. The fuselage12additionally includes an outer surface or skin38. Alternatively, the aircraft10may additionally or alternatively include any other suitable configuration. For example, in other embodiments, the aircraft10may include any other configuration of stabilizer.

The aircraft10includes a propulsion system50having a first propulsor200and a second propulsor200. As shown, each of the propulsors200is configured as an under-wing mounted propulsor and may be disposed in or may include a corresponding nacelle202of the aircraft10. One propulsor200is mounted, or configured to be mounted, to the first side24of the aircraft10, such as to the first wing20of the aircraft10. The propulsion system50includes an electrical power bus58to supply current to the propulsors200. The propulsion system50may include one or more energy storage devices55(such as one or more batteries or other electrical energy storage devices) electrically connected to the electrical power bus58for providing electrical power to the propulsors200. As shown, the aircraft10does not include any turbine engine or other fuel-consuming engine that operates to generate thrust to propel the aircraft10. Optionally, the aircraft10can include one or more turbine engines, turbofans, or the like, for providing thrust and/or generating electric current to power the propulsors200.

FIG. 2illustrates a front view of one embodiment of one of the propulsors200shown inFIG. 1.FIG. 3illustrates a cross-sectional view of one embodiment of the propulsor200shown inFIG. 2. The propulsor200includes a spinner204located within the nacelle202. The spinner204is coupled with several fan blades206that extend radially outward from the spinner204. These fan blades206also extend radially outward from a center line226or axis of rotation of the spinner204. The spinner204houses a fan hub208to which inner ends210of the fan blades206are coupled. Outlet guide vanes212may radially extend from the spinner204toward the nacelle202and may be connected with the fan blades206by thrust bearings214.

A rim-driven motor216includes a stator218that is at least partially disposed within the nacelle202. The stator218can be positioned along an inner surface220of the nacelle202or closer to the inner surface220of the nacelle202than an opposite outer surface222of the nacelle202. As shown inFIG. 3, the stator218extends around or encircles the center line226of the spinner204and fan hub208. The motor216also includes magnets, such as permanent magnets, disposed in fan shrouds224of the fan blades206. The fan shrouds224are located at or on ends of the fan blades206that are opposite the inner ends210. For example, the fan shrouds224that include the magnets may be located closer to the nacelle202than the spinner204or fan hub208. As described herein, the stator218includes conductive coils that are powered by separate inverter power stages of a distributed inverter of the propulsor200to rotate the magnets in the fan shrouds224(and, therefore, rotate the fan blades206) to generate thrust to the aircraft10.

As shown, the nacelle202is located radially outside of the spinner204and the fan hub208(relative to the center line226) so that air flow228can pass between the spinner204and the inner surface220of the nacelle202. Additional air flow can extend over the outer surface222of the nacelle202. This air flow can help cool and/or reject heat from the components of the propulsor200. For example, the coils, buses, inverter power stages, gate drivers, and the like, that are described herein may become heated during operation of the propulsor200due to the electric current flowing and/or induced in one or more of these components. Placing these components in the nacelle202and in thermal contact with the surfaces220,222of the nacelle202provide the components with a much larger surface area over which to dissipate or reject heat into the external environment. For example, placing these components inside the spinner204or hub208can significantly decrease the surface area through which thermal energy can be transferred to the external environment relative to the much larger surface area of the inner and outer surfaces220,222of the nacelle202.

FIG. 4illustrates part of one embodiment of the motor216shown inFIG. 2. The portion of the motor216that is shown inFIG. 3includes one of several conductive coils400through which AC is conducted to temporarily induce magnetic fields. These magnetic fields interact with the permanent magnetic fields provided by one or more permanent magnets402that are embedded in the shroud224of a fan blade206. This interaction can move the fan blade206to rotate the spinner204around the center line226to generate thrust for propelling the aircraft10.

The coil400is conductively coupled with one of several inverter power stages404of a distributed inverter assembly (described below) by one or more conductive buses406. Alternatively, each of the inverter power stages404can represent an inverter. In one embodiment, the coils400are closely coupled with the inverter power stages404. The conductive bus406may represent part of the power bus58shown inFIG. 1or may represent another conductive bus. The inverter power stage404converts DC received from a source (e.g., the energy storage device55via the power bus58) into a single phase of AC. This single phase of AC is conducted via the bus406to and through the coil400to create the temporary magnetic fields described above.

FIGS. 5 and 6illustrate one embodiment of a distributed inverter assembly500of the propulsor200. The distributed inverter assembly500includes several circuit sets502of the inverter power stages404, gate drivers504(not shown inFIG. 6), and the coils400. Only a single inverter power stage404is shown inFIG. 5, but several of the inverter power stages404are provided in one embodiment.

In the illustrated embodiment, each set502of the distributed inverter assembly500includes an inverter power stage404separately controlled by a separate gate driver504and separately coupled with a different coil400in the stator218. Stated differently, each coil400is separately powered with a different, single inverter power stage404instead of multiple coils400receiving one or more phases of AC from the same inverter power stage404. Alternatively, two or more, but fewer than all, of the coils400may be connected with the same inverter power stage404such that multiple, but not all, of the coils400are powered by the phase of AC supplied from the same inverter power stage404. The coils400may be separate from each other such that current conducted in one coil400is not conducted to any other coil400.

Each inverter power stage404is connected with a separate gate driver504. Alternatively, two or more inverter power stages404can be connected with the same gate driver504. The inverter power stage404can be connected with the gate driver504by one or more optical connections518, such as by one or more optical fibers. The use of optical fibers can reduce the effects of electromagnetic interference on the several gate drivers504communicating with the several inverter power stages404to ensure that the inverter power stages404are controlled to rotate the fan blades206. Alternatively, the inverter power stages404can be connected with the gate drivers504using conductive connections (e.g., buses) or other types of connections.

The gate driver504is connected with DC buses506,508,510, including a positive DC bus506, a negative DC bus508, and a neutral bus510. Each gate driver504can include a connection512with the positive DC bus506that does not connect with the negative DC bus508or the neutral bus510, a connection514with the negative DC bus508that does not connect with the positive DC bus506or the neutral bus510, and a connection516with the neutral bus510that does not connect with the positive DC bus506or the negative DC bus508.

The buses506,508,510can represent part of the power bus58shown inFIG. 1to receive DC from the energy storage device55, can be connected with the power bus58to receive DC from the energy storage device55, or can represent other conductive bodies. While only a single set of the connections512,514,516between the gate drivers504and the buses506,508,510are shown inFIG. 6, each of the gate drivers504can include a set of the connections512,514,516with the corresponding buses506,508,510. As shown inFIGS. 5 and 6, multiple or all gate drivers504can be connected with the same (e.g., common) positive DC bus506, the same negative DC bus508, and the same neutral bus510. Alternatively, two or more of the gate drivers504can be connected with different positive DC buses506, different negative DC buses508, and/or different neutral buses510.

The gate driver504controls conduction of positive DC from the positive DC bus506, conduction of negative DC from the negative DC bus508, and connects the inverter power stage404with the neutral bus510so that the inverter power stage404can convert the positive and negative DC into a single phase of AC current that is conducted to and through the corresponding coil400. As described above, this helps drive the magnets402to rotate the fan blades206around the center line226. The gate drivers504can be controlled by control signals sent from the controller62, which may be based on manually input and/or automatically determined throttle instructions or directives for the aircraft10.

As shown inFIG. 6, the coils400, inverter power stages404, gate drivers504, and buses406,506,508,510can be disposed inside the nacelle202between the inner and outer surfaces220,222of the nacelle202. These components may be in thermal contact with the surfaces220and/or222of the nacelle202so that heat generated by these components can be transferred to the surfaces220and/or222and dissipated outside of the propulsor200.

The separate coils400, separate inverter power stages404, and separate gate drivers504can provide for increased reliability of the motor216relative to other non-distributed motor designs. For example, the failure of one or some (but not all) coils400, the failure of one or some (but not all) inverter power stages404, and/or the failure of one or some (but not all) gate drivers504does not prevent the motor216from continuing to rotate the fan blades206. The failure an inverter power stage404, the failure of a gate driver504, the interruption or break of a connection between the inverter power stage404and the coil400that was connected with the inverter power stage404, and/or the interruption or break of the conductive loop formed by the coil400may prevent that inverter power stage404, that gate driver504, and/or that coil400from operating to generate a magnetic field that rotates the fan blades206. But, this failure or interruption will not prevent or stop other gate drivers504, corresponding inverter power stages404, and corresponding coils400from operating to generate magnetic fields that rotate the fan blades206. While the motor216may operate to produce less peak power in such a failure or interrupted state, the motor216may continue to operate to generate thrust to keep propelling the aircraft10.

In the embodiment shown inFIG. 4, the magnets402are disposed within the fan shrouds224of the fan blades206in locations that are radially inside of the inner surface220of the nacelle202. For example, the magnets402can be located between the inner surface220of the nacelle202and the center line226.

FIG. 7illustrates another embodiment of a fan shroud724of the fan blades206. The fan shrouds724can be coupled with the same fan blades206as the shroud224. A nacelle702shown inFIG. 7can be used in place of the nacelle202shown inFIGS. 2, 3, 4, and 6. One difference between the nacelle702and the nacelle202is that the nacelle702includes a recessed channel730. This channel730can extend around the center line226of the fan hub208or spinner204such that the channel730extends along a path that encircles the center line226around and radially outside of the fan blades206.

The fan shroud724includes a radial extension732that outwardly protrudes from the outer end of the fan shroud724away from the center line226. The radial extension732is shaped to fit and move within the channel730in the nacelle702without contacting or rubbing against any surface of the nacelle702. The magnets402can be located on opposite sides of the extension732such that the magnets402face away from each other. Conductive coils700located in a stator718can be used in place of the coils400in the stator218. The cross-sectional view shown inFIG. 7illustrates a plane that bisects each coil700. As described above, each coil700can be separately closely coupled with a different inverter power stage404, which can be separately coupled with a different gate driver504.

The stator718can include several coils700located at different positions in the path that circumferentially extends around the center line226. For example, the stator718can include more than just a single coil700on each side of the channel730. In the illustrated embodiment, the stator718includes coils700on both sides of the channel730. Alternatively, the stator718may have coils700on only one side of the channel730.

FIG. 8illustrates another embodiment of a fan shroud824of the fan blades206. The fan shrouds824can be coupled with the same fan blades206as the shroud224. A nacelle802shown inFIG. 8can be used in place of the nacelle202shown inFIGS. 2, 3, 4, and 6. One difference between the nacelle802and the nacelle202is that the nacelle802includes two recessed channels830. Each of the channels830can extend around the center line226of the fan hub208or spinner204such that each channel830extends along a different path that encircles the center line226around and radially outside of the fan blades206.

The fan shroud824includes multiple radial extensions832that outwardly protrude from the outer end of the fan shroud824away from the center line226. Each of the radial extensions832is shaped to fit and move within a different one of the channels830in the nacelle802without contacting or rubbing against any surface of the nacelle802. One or more magnets402can be located in each of the extensions832on opposite sides of a stator818in the nacelle802such that the magnets402face each other. Conductive coils800located in the stator818can be used in place of the coils400in the stator218. As shown, the coils800are located between the magnets402in the stator818. The cross-sectional view shown inFIG. 8illustrates a plane that bisects each coil800. As described above, each coil800can be separately closely coupled with a different inverter power stage404, which can be separately coupled with a different gate driver504. The stator818can include several coils800located at different positions in the path that circumferentially extends around the center line226. For example, the stator818can include more than just a single coil800facing each magnet402.

FIG. 9illustrates a flowchart of one embodiment of a method900for providing a motor-driven propulsor of an aircraft. The method900can be used to create one or more embodiments of the propulsors200described herein. The operations of the method900can be performed in a different order than what is shown in the flowchart. For example, the order of two or more of the operations may be switched with each other and/or two or more of the operations may be performed concurrently and/or simultaneously.

At902, magnets are placed into fan shrouds of fan blades that are connected with a fan hub. The magnets can be permanent magnets located in fan shrouds that are radially inside of a nacelle of the aircraft. The fan shrouds may be closer to the nacelle than the fan hub and may face the inner surface of the nacelle.

At904, a stator is positioned in the nacelle of the aircraft. For example, conductive coils may be positioned in a housing that extends around and encircles the fan blades, the spinner, and the fan hub. The conductive coils can be separate from each other such that current conducted in one coil is not conducted from that coil to another coil.

At906, several inverter power stages of a distributed inverter assembly are coupled with several gate drivers. Each of the inverter power stages can be coupled with a separate gate driver of the gate drivers. The connections between the inverter power stages and the gate drivers can be made using an optical connection, such as an optical fiber, to allow for the gate drivers to control the inverter power stages using light signals. Alternatively, the inverter power stages can be conductively coupled with the gate drivers.

At908, the inverter power stages are conductively coupled with the coils in the stator. Each inverter power stage can be conductively coupled with a different coil so that failure of a gate driver, inverter power stage, coil, or connection therebetween does not prevent other coils inverter power stages, or gate drivers from continuing to operate to generate thrust by rotating the fan blades.

In one embodiment, a motor driven propulsor of an aircraft is provided. The propulsor includes magnets disposed in fan shrouds of fan blades connected with a fan hub, a stator having individual conductive coils in a nacelle located radially outside of the fan hub, and a distributed inverter assembly having several inverter power stages and gate drivers, each of the inverter power stages coupled with a separate gate driver of the gate drivers and a separate coil of the coils in the stator. Each of the gate drivers is configured to individually control supply of direct current to the corresponding inverter power stage. Each of the inverter power stages is configured to convert the direct current supplied to the inverter power stage to an alternating current that is supplied to the corresponding coil in the stator to rotate the magnets and the fan blades around a center line of the fan hub for propelling the aircraft.

Optionally, each of the inverter power stages is close coupled with the corresponding coil to which the inverter power stage is conductively connected. The nacelle can be configured to transfer heat generated in the coils of the stator over a large surface area that is outside of the fan blades and the fan hub. The coils of the stator and the inverter power stages may be thermally coupled with a radially inward surface of the nacelle and with a radially outward surface of the nacelle.

Optionally, the inverter power stages and the gate drivers are coupled with a direct current bus, and the inverter power stages, the gate drivers, and the direct current bus are located within the nacelle. The gate drivers can all be connected to a common positive direct current bus, a common negative direct current bus, and a common neutral bus. The magnets may be disposed within the fan shrouds of the fan blades in locations that are radially inside of an inner surface of the nacelle.

Optionally, the nacelle includes a channel that extends around the center line of the fan hub. The magnets can be located in radial protrusions of the fan shrouds that radially project away from the center line of the fan hub and into the channel in the nacelle. The conductive coils in the stator may be located on opposite sides of the channel in the nacelle.

Optionally, the nacelle includes channels that extend around the center line of the fan hub. The magnets can be located in radial protrusions of the fan shrouds that radially project away from the center line of the fan hub and into the channels in the nacelle. The conductive coils in the stator may be located between the channels in the nacelle.

Optionally, the inverter power stages are connected with the gate drivers by optical fibers and the gate drivers are configured to control supply of the direct current to the inverter power stages using control signals communicated via the optical fibers.

In one embodiment, a method for providing a motor driven propulsor of an aircraft is provided. The method includes placing magnets disposed in fan shrouds of fan blades connected with a fan hub, positioning a stator having individual conductive coils in a nacelle located radially outside of the fan hub, and coupling several inverter power stages of a distributed inverter assembly with several gate drivers. Each of the inverter power stages is coupled with a separate gate driver of the gate drivers. The method also includes conductively coupling each of the inverter power stages with a different coil of the coils in the stator. Each of the gate drivers is coupled with a different inverter power stage of the inverter power stages to individually control supply of direct current to the corresponding inverter power stage. Each of the inverter power stages is coupled with the corresponding gate driver and the corresponding coil to convert the direct current supplied to the inverter power stage to an alternating current that is supplied to the corresponding coil in the stator to rotate the magnets and the fan blades around a center line of the fan hub for propelling the aircraft.

Optionally, conductively coupling each of the inverter power stages with the different coil includes close coupling the inverter power stage with the corresponding coil. The coils of the stator can be positioned in the nacelle and the inverter power stages are coupled with the coils such that the coils and the inverter power stages are thermally coupled with a radially inward surface of the nacelle and with a radially outward surface of the nacelle.

The method also can include coupling the inverter power stages and the gate drivers with a direct current bus such that the inverter power stages, the gate drivers, and the direct current bus are located within the nacelle. The nacelle may include one or more channels that extend around the center line of the fan hub, and wherein the magnets are positioned in radial protrusions of the fan shrouds that radially project away from the center line of the fan hub and into the one or more channels in the nacelle. Optionally, the inverter power stages are coupled with the gate drivers by optical fibers.

In one embodiment, a motor driven propulsor includes magnets disposed in fan shrouds of fan blades connected with a fan hub, a stator having individual conductive coils in a nacelle located radially outside of the fan hub, and a distributed inverter assembly having several inverter power stages. Each of the inverter power stages is close coupled with a separate coil of the coils in the stator. Each of the inverter power stages is configured to power the corresponding coil in the stator to rotate the magnets and the fan blades around a center line of the fan hub for generating a propulsive force. The inverter power stages are separately coupled with the coils in the stator such that one or more inverter power stages continue powering the corresponding coils to continue generating the propulsive force after failure of at least one of the inverter power stages.

Optionally, the coils of the stator and the inverter power stages are thermally coupled with a radially inward surface of an aircraft nacelle and with a radially outward surface of the nacelle.

As used herein, an element or step recited in the singular and proceeded with the word “a” or “an” should be understood as not excluding plural of said elements or steps, unless such exclusion is explicitly stated. Furthermore, references to “one embodiment” of the presently described inventive subject matter 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,” “including,” or “having” (or like terms) an element, which has a particular property or a plurality of elements with a particular property, may include additional such elements that do not have the particular property.

As used herein, terms such as “system” or “controller” may include hardware and/or software that operate(s) to perform one or more functions. For example, a system or controller may include a computer processor or other logic-based device that performs operations based on instructions stored on a tangible and non-transitory computer readable storage medium, such as a computer memory. Alternatively, a system or controller may include a hard-wired device that performs operations based on hard-wired logic of the device. The systems and controllers shown in the figures may represent the hardware that operates based on software or hardwired instructions, the software that directs hardware to perform the operations, or a combination thereof.

As used herein, terms such as “operably connected,” “operatively connected,” “operably coupled,” “operatively coupled” and the like indicate that two or more components are connected in a manner that enables or allows at least one of the components to carry out a designated function. For example, when two or more components are operably connected, one or more connections (electrical and/or wireless connections) may exist that allow the components to communicate with each other, that allow one component to control another component, that allow each component to control the other component, and/or that enable at least one of the components to operate in a designated manner.