Patent Grant
7571707
Some internal combustion engines can vary operation of one or more cylinders between different modes of operation depending on the operating conditions of the engine or other vehicle systems. As one example, at least a portion of the engine cylinders can be transitioned between a spark ignition (SI) mode and a homogeneous charge compression ignition (HCCI) mode in response to the level of torque requested by the vehicle operator. As another example, the number of firing cylinders may be reduced, under some conditions, by the use of cylinder deactivation, in order to conserve fuel and improve efficiency of the engine, while the number of firing cylinders may be increased where a greater amount of engine torque is requested. In this way, advantages associated with each mode of operation can be achieved while reducing or eliminating the disadvantages of each of the modes by selectively utilizing mode transitions.
However, the inventors herein have recognized some issues relating to the above approaches. Specifically, in some conditions, engine transitions between different modes of operation may cause torque transients or discontinuities that can result in increased longitudinal acceleration of the vehicle and/or excitation of the vehicle driveline. As such, the mode transitions may, in some cases, be perceived by the vehicle operator, may increase mechanical wear of vehicle components, or may increase the likelihood of mechanical malfunction, due to the torque transients occurring during the transition.
In at least one approach described herein, at least some of the above issues may be addressed by a method of operating an engine having a plurality of cylinders, the method comprising transitioning the engine from a first mode to a second mode; and temporarily adjusting an amount of torque produced by a cylinder of the engine for at least one cycle responsive to a difference in an amount of torque produced by a previous firing cylinder and a subsequent firing cylinder. In this way, one or more cylinders of the engine may be adjusted before or after the transition responsive to the torque signature of the first mode and the second mode, thereby reducing torque transients that may result in excitation of the driveline including the transmission and/or increased longitudinal acceleration of the vehicle. Note that the different modes of operation may include a change in combustion mode, number of firing cylinders, and/or the number of strokes performed per cycle.
As another approach described herein, at least some of the above issues may be addressed by a method of operating an engine having a plurality of cylinders, wherein the engine is configured to provide torque to a drive wheel of a vehicle via a transmission, the method comprising transitioning the engine from a first mode to a second mode; and adjusting an amount of torque produced by at least one of a last firing event of a cylinder in the first mode and a first firing event of a cylinder in the second mode responsive to a condition of the transmission. In this way, the engine may be controlled during transitions between different modes of operation in response to a condition of the transmission such as the selected gear ratio or the amount of slip provided by a transmission clutch, for example.
As yet another approach described herein, at least some of the above issues may be addressed by a method of operating an engine having a plurality of cylinders, the method comprising transitioning at least one cylinder of the engine from a first mode to a second mode; and temporarily adjusting a peak amount of torque produced by one of a last firing cylinder of the first mode and a first firing cylinder of the second mode for at least one cycle responsive to a difference between a first quantity of firing cylinders in the first mode and a second quantity of firing cylinders in the second mode. In this way, the engine may be controlled during transitions between modes having different quantities of firing cylinders, such as may be provided by a variable displacement engine.
It should be appreciated that the several approaches provided by the above summary are non-limiting examples of the various concepts that will be further described in the detailed description and are not intended to define the scope of the present application or claimed invention.
Referring to
Combustion chamber 30 may receive intake air from intake passage 44 via intake manifold 42 and may exhaust combustion gases via exhaust passage 48. Intake passage 44 and exhaust passage 48 can selectively communicate with combustion chamber 30 via respective intake valve 52 and exhaust valve 54. In some embodiments, combustion chamber 30 may include two or more intake valves and/or two or more exhaust valves. The position of intake valve 52 may be controlled by controller 12 via electric valve actuator (EVA) 51. Further,
Fuel injector 66 is shown coupled directly to combustion chamber 30 for injecting fuel directly therein in proportion to the pulse width of signal FPW received from controller 12 via electronic driver 68. In this manner, fuel injector 66 provides what may be referred to as direct injection (DI) of fuel into combustion chamber 30. The fuel injector may be mounted at other suitable location within the combustion chamber including the side or the top of the combustion chamber, for example. Fuel may be delivered to fuel injector 66 by a fuel system (not shown) including a fuel tank, a fuel pump, and a fuel rail. In some embodiments, combustion chamber 30 may alternatively or additionally include a fuel injector arranged in intake passage 44 in a configuration that provides what may be referred to as port injection (PI) of fuel into the intake port upstream of combustion chamber 30.
Intake manifold 42 may include a throttle 62 having a throttle plate 64. In this particular example, the position of throttle plate 64 may be varied by controller 12 via a signal provided to an electric motor or actuator included with throttle 62, a configuration that may be referred to as electronic throttle control (ETC). Thus, throttle 62 may be operated to vary the intake air provided to combustion chamber 30 among other engine cylinders. The position of throttle plate 64 may be provided to controller 12 by throttle position signal TP. Intake manifold 42 may include a mass air flow sensor 120 and a manifold air pressure sensor 122 for providing respective signals MAF and MAP to controller 12.
Ignition system 88 can provide an ignition spark to combustion chamber 30 via spark plug 92 in response to spark advance signal SA from controller 12, under select operating modes. Though spark ignition components are shown, in some embodiments, combustion chamber 30 or other combustion chambers of engine 10 may be operated in an alternative modes including what may be referred to as compression ignition, which may not necessarily include the use of an ignition spark to initiate combustion.
Exhaust gas sensor 126 may be coupled to exhaust passage 48 upstream of emission control device 70. Sensor 126 may be other suitable sensor for providing an indication of exhaust gas air/fuel ratio such as a linear oxygen sensor or UEGO (universal or wide-range exhaust gas oxygen), a two-state oxygen sensor or EGO, a HEGO (heated EGO), a NOx, HC, or CO sensor. An emission control device 70 can be arranged along exhaust passage 48 downstream of exhaust gas sensor 126. Device 70 may include a three way catalyst (TWC), NOx trap, particulate filter, etc. In some conditions, emission control device 70 may be periodically reset by operating one or more cylinders of the engine at a particular air/fuel ratio.
Controller 12 is shown in
As described above,
In some conditions, one or more cylinders of engine 10 may be controlled to vary operation between different modes based on the operating conditions of the engine. As one example, a cylinder of the engine may be transitioned between two or more different combustion modes, which may include spark ignition (SI) of a homogeneous lean charge, spark ignition of a stratified lean charge, spark ignition of a substantially stoichiometric charge, compression ignition including homogeneous charge compression ignition (HCCI) or premixed charge compression ignition (PCCI), multi-stroke modes (e.g. 2 stroke, 4 stroke, 6 stroke, or more strokes), deactivation or disabled modes (e.g. where combustion is discontinued for one or more cycles), or other suitable combustion modes. These different combustion modes may be used to achieve improved performance under a variety of engine operating conditions. For example, efficiency and/or combustion stability may be improved while emissions, misfire, and/or noise and vibration harshness (NVH) may be reduced.
Spark ignition, for example, may be used to achieve stable combustion at substantially low or high engine load or speed conditions due to the use of an ignition spark for the initiation of combustion with the cylinder. Spark ignition of a homogeneous lean charge as described herein may include combustion of a substantially homogeneous mixture of air and fuel via a sparking device, whereby the mixture includes less than a stoichiometric amount of fuel compared to air. Spark ignition of a stratified lean charge as described herein may include combustion of a stratified mixture including less than a stoichiometric amount of fuel compared to air via a sparking device. Spark ignition of a stoichiometric mixture of air and fuel as described herein may include combustion of a mixture including approximately a stoichiometric amount of fuel compared to air, where ignition of the mixture is initiated by a sparking device.
While spark ignition may be used to achieve reliable combustion, the efficiency and/or emission quality may be reduced, in some conditions, as compared to other operating modes such as HCCI. HCCI as described herein may include combustion of a substantially homogeneous mixture of air and fuel and may include less than a stoichiometric amount of fuel compared to air, whereby ignition of the mixture is initiated via autoignition without necessarily requiring a sparking device. Instead, autoignition may be initiated by compression performed by the piston without necessarily requiring an ignition spark to be performed by the sparking device. However, in some conditions, an ignition spark may be used to assist compressed air and fuel mixture to reach autoignition.
In an engine with electronic valve actuation, EVA or iEVA, it is also possible to operate each cylinder in one of a firing or a non-firing state via cylinder deactivation. Cylinder deactivation as described herein may include the operation of discontinuing combustion within the cylinder for one or more cycles. Deactivation of the cylinder may include discontinuing the fuel delivery and/or sparking operation within the cylinder during select conditions. For example, deactivation of one or more cylinders may be used where the level of requested torque is relatively low. In this way, fuel efficiency may be increased, under some conditions, where less than a threshold level of torque is requested by deactivating one or more cylinders of the engine.
A multi-stroke mode as described herein may include operating one or more cylinders of the engine between a first cycle having a first number of strokes and a second cycle having a second different number of strokes, based on operating conditions of the engine. Alternatively or in addition, a multi-stroke mode may include operation of a first portion of cylinders with a cycle having a first number of strokes and a second portion of cylinders with a cycle having a second different number of strokes. For example, a first bank of cylinders may operate with a four-stroke cycle while a second bank of cylinders may operate with a six-stroke cycle and/or may vary operation between the four-stroke and six stroke cycles.
Still other combustion modes are possible. As one example, one or more cylinders of the engine may operate in a diesel cycle mode whereby fuel is injected into a compressed air charge to initiate combustion.
In some conditions, a first portion of the engine cylinders may be operated in one of the above described combustion modes while a second portion of the cylinders may be operated in another of the combustion modes. Further, during other conditions, an engine may utilize three or more different combustion modes among the various cylinders. As one example, a first bank of cylinders may be operated in HCCI mode while a second bank of cylinders may be operated in one of the SI modes. As yet another example, a first bank of the cylinders may be operated in one of the SI modes, while a first portion of the cylinders of a second bank are operated in HCCI mode and a second portion of cylinders of the second bank are deactivated.
In some embodiments, one or more cylinders of the engine may be controlled to vary operation between two or more combustion modes based on operating conditions of the engine. As one example, a first bank of cylinders may be operated in SI mode while a second bank of cylinders may be transitioned between an SI mode, HCCI mode and/or deactivation. Thus, it should be appreciated that other suitable modes of operation may be used among the various cylinders of the engine.
In this way, the engine may be controlled to vary the operating mode of some or all of the cylinders in numerous ways to achieve the benefits of each mode of operation. However, in some conditions, the transition of one or more cylinders between different modes of operation may cause torque transients due to one or more reasons.
As one example, torque transients may be caused by a transition of at least one cylinder of the engine between modes when the steady-state or average torque before and after the transition are not matched. For example, if the engine is not controlled during the transition between modes, a net increase or decrease in level of torque produced by the engine may occur. Therefore, in order to reduce the torque transients, one or more operating parameters of the engine may be adjusted in response to the transition in order to match the average torque produced by the engine before and after the transition.
As another example, torque transients may occur as a result of excitation of the driveline due to a transition of one or more cylinders between modes. For example, where a change in the torque pulsation characteristic occurs, a vibration mode of the driveline may be excited.
Referring now to
As one example, due to the sensitivity of the human body to longitudinal vibration, particularly in the range of 2 to 8 Hz, the vehicle operator and/or passengers may experience degraded drive feel if the lowest frequency driveline vibration mode (i.e. the shuffle mode) is excited.
To address some of the above issues, several approaches will be described for reducing the excitation of the driveline during a change in operating mode of the engine. While these approaches may include a method for reducing the particular excitation of the shuffle mode and the longitudinal acceleration during a mode transition, it should be appreciated that these approaches may be used to reduce excitation of other driveline frequencies.
In the various approaches described herein, an engine can be operated to provide pre and/or post mode transition engine torque modulation by adjusting the intake and/or exhaust valve timing (or exhaust cam phaser(s) in the case of iEVA), as well as the fuel, spark and/or transmission state. By controlling the valve timing in an EVA or iEVA engine it is possible to control the cylinder air charge and residual level as well as the start of combustion (SOC) timing (e.g. the 50% burn duration timing) and cylinder charge temperature for some combustion modes on an individual cylinder basis. Further, if at least some of the engine cylinders include direct injection, then the use of spark ignition of a stratified lean mixture or multi-stroke operation (e.g. six-stroke) among other modes of operation may be performed on a cylinder-by-cylinder basis. By controlling the EVA or iEVA valve timing, fuel and/or spark, the pre and post mode transition torque can be calibrated to reduce the transmission output peak-to-peak torque, reduce the variation in the vehicle longitudinal acceleration (e.g. maintain a vibration dose valve (VDV) of less than 0.5 during the transition), reduce the excitation of at least the lowest frequency driveline mode (e.g. the shuffle mode) or other frequencies, and/or provide a damping action to damp-out driveline modes that are excited.
Referring now to
If the answer at 512 is no, the control system may continue to monitor the operating conditions to determine whether a transition is requested based on the mode transition logic. Alternatively, if the answer at 512 is yes, the average steady state engine output torque of Mode k may be matched to the average steady state output torque of Mode j at 514, for example, by adjusting the valve timing (e.g. via EVA), fuel (e.g. amount and/or timing), and/or spark timing, among other engine parameters. For example, the average steady state torque may be increased or decreased over one or more cycles after the transition to Mode k to more closely match the average steady state torque of Mode j. As another example, the average steady state torque of Mode j may be increased or decreased over one or more cycles before the transition to Mode k to more closely match the average steady state torque of Mode k. As yet another example, the average steady state torque of Mode j and Mode k may be adjusted accordingly so that they are more closely matched across the transition.
At 516 and 518 it may be judged whether the number of firing cylinders (i.e. N_fire) of the engine is increasing, decreasing, or remaining the same as the engine transitions from Mode j to Mode k. If it is judged at 516 that the number of firing cylinders for Modes j and k are the same across the transition, then the routine proceeds to 528. Alternatively, if the number of firing cylinders changes in response to the transition, then it may be judged whether the number of firing cylinders in Mode j is greater than the number of firing cylinders in Mode k at 518. In other words, it may be judged whether the number of firing cylinders is decreasing during the transition. For example, one or more cylinders of the engine may be deactivated, whereby combustion is discontinued in the cylinder for a prescribed period.
If it is judged at 518 that the number of firing cylinders in Mode k is to be greater than Mode j, then the answer at 518 is no. As such, the final cylinder of the Mode j operation may be scheduled to be a non-firing cylinder at 520 and the first cylinder of the Mode k operation may be scheduled to be a firing cylinder at 522. In this way, where the number firing cylinders is increasing in response to the transition, then at least the last cylinder in the first mode may not be fired and the first cylinder in the second mode may be fired. Further, the charge of at least the first firing cylinder of Mode k operation can be increased at 524, for example, by adjusting one or more of the valve timing and/or lift to increase air charge, spark timing may be advanced and/or the fuel pulse width may be increased to deliver additional fuel to the cylinder. In this way, the torque produced by at least the first cylinder in Mode k may be increased to more closely match the torque produced by the engine in Mode j. Thus, excitation of the driveline, particularly the shuffle mode may be reduced or cancelled. Thereafter, the charge may be decreased for one or more subsequent cylinders in Mode k. As the engine is transitioned to Mode k, the spark and/or fuel can be adjusted at 526 for the particular mode of operation as indicated by Mode k in order to control engine torque, whereby the routine returns to the mode transition logic at 510 as described above.
Returning to 518, if it is judged that the number of firing cylinders is decreasing from Mode j to Mode k, then the last cylinder of the Mode j operation may be scheduled as a firing cylinder at 530 and the first cylinder of the Mode k operation may be scheduled as a firing cylinder at 532. Further, the charge of at least the first firing cylinder of Mode k operation can be decreased at 534, for example, by adjusting one or more of the valve timing and/or lift to decrease air charge, spark timing may be retarded and/or the fuel pulse width may be decreased to deliver less fuel to the cylinder. Thereafter, the charge may be increased for one or more subsequent cylinders of Mode k. As the engine is transitioned to Mode k, the spark and/or fuel can be adjusted at 526 for the particular mode of operation as indicated by Mode k in order to control engine torque, whereby the routine returns to the mode transition logic at 510 as described above.
Returning to 516, if it is judged that the number of firing cylinders is to remain the same across the transition from Mode j to Mode k, then the routine may proceed to 528. At 528, it may be judged whether the peak to peak engine torque (i.e. Tor_PP) for Mode j is less than the peak to peak engine torque for Mode k. If the answer yes, then the routine may proceed to 534 where the charge of at least the first cylinder of Mode k may be decreased, thereby reducing the torque produced by the cylinder. Alternatively, if the answer at 528 is no, the routine may proceed to 524 where the charge of at least the first cylinder of Mode k may be increased, thereby increasing the torque produced by the cylinder. In this way, the torque produced by the engine for at least the first firing event of Mode k may be adjusted to more closely match the torque produced by the last cylinder of Mode j, thereby reducing excitation of the vehicle driveline and/or longitudinal acceleration caused by the transition.
Note that with regards to a transition involving a change in the number of strokes performed by one or more of the cylinders, the transition may be handled as either a change in peak to peak torque, for example, as indicated at 528 where the number of firing cylinders is not changing in response to the transition or where the number of firing cylinders is changing due to the transition, then the routine may proceed to 518. For example, where the engine is transitioning from a first mode where the cylinders are operated by HCCI with six strokes per cycle to a second mode where the cylinders are operated with four strokes per cycle, the charge of the first cylinder in the second mode may be increased (e.g. as indicated at 524) where the peak to peak torque is decreasing across the transition or the charge may be decreased (e.g. as indicated at 534) where the peak to peak torque is increasing across the transition. For example, where the number of strokes is increasing, the transition may be treated as a decrease in peak to peak torque, while during transitions where the number of strokes is decreasing, the transition may be treated as an increase in peak to peak torque, for example, as judged at 528. In this way, the approaches described above with reference to
Referring now to
As the number of cylinders is decreasing across the transition, for example, as may be judged at 518 of
In this way, by increasing or decreasing the amount of torque produced by the first firing cylinder in the second mode, the longitudinal acceleration and/or excitation of the driveline may be reduced.
As described above with reference to
Further, it should be appreciated that the torque produced by the second and/or subsequent firing cylinders of the second mode may also be increased or decreased to reduce the rate of change in the torque produced by the engine resulting from a transition. For example, the torque produced by a second firing cylinder of the second mode may be controlled to be between the torque or within the range of torque produced by the previous (i.e. first firing cylinder) and subsequent (i.e. third firing cylinder) of the second mode.
In addition to or as an alternative to the adjustment of the torque produced by the first and/or subsequent firing cylinders of the second mode, the last firing cylinder of the first mode may be adjusted to reduce the torque transients caused by the transition.
In particular,
Similarly,
In some embodiments, the various approaches described above with reference to
At 1612, it may be judged whether a transition is requested of one or more cylinders. If the answer is no, then the routine may return to 1610. Alternatively, if the answer at 1612 is yes, then the control system may vary operation (e.g. timing, lift, etc.) of one or more of the intake and/or exhaust valves at 1614, the spark timing at 1616, and/or the fuel injection amount and/or timing at 1618 to modulate torque based on the requested transition. As described above, the modulation of torque may be performed prior to the transition, during the transition, and/or after the transition to achieve a reduction in the torque transients. Note that valve operation may be varied by varying the valve timing, valve lift, and/or valve lift duration via the EVA system or by cam actuation for the exhaust valves in the case of an iEVA configuration. As one example, the torque may be temporarily adjusted or modulated so that the peak torque produced by each firing cylinder is more closely matched between the previous firing cylinder and the subsequent firing cylinder. Note that the amount of the temporary adjustment may be based on the difference between the peak amount of torque produced by the immediately previous firing cylinder and the immediately subsequent firing cylinder. As yet another example, the amount of the temporary adjustment may be based on the transmission state including the selected gear and/or transmission slip. For example, the amount of the temporary adjustment of peak torque may be increased or decreased with increasing transmission slip and/or gear ratio depending on the direction and/or type of transition to reduce longitudinal acceleration of the vehicle and/or to avoid the various natural frequencies of the transmission as illustrated in
Note that the engine torque may be modulated differently depending on the particular operating mode of the cylinder and/or engine. As one example, where a cylinder of the engine is transitioned from an SI mode of operation to HCCI mode, spark timing control may be used to modulate or temporarily adjust torque before the transition while operating in SI mode and the use of fueling control (e.g. fuel amount and/or timing of deliver) may be used to modulate torque after the transition when operating in HCCI mode. For example, some operating parameters may not be available for adjustment in some modes, such as the use of spark timing during HCCI mode where the use of spark has been discontinued. In this way, a suitable engine parameter may be adjusted for the particular operating mode of the cylinder. In other words, some control parameters may not cause a modulation of torque during some modes or may be more or less sensitive than desired. Further still, the use of some control parameters during some modes may be more prone to misfire, noise and vibration harshness, etc. and may therefore be avoided or may be used to a lesser extent.
While torque may be modulated by adjusting one or more parameters that are suitable for the particular operating mode, torque may be increased or decreased differently depending on the type of adjustment. As one example, the torque produced by the engine may be reduced, during some conditions (e.g. SI mode), by further retarding the spark timing of one or more cylinders of the engine. Conversely, engine torque may be increased by advancing the spark timing, under some condition. As another example, charge temperature may be controlled by varying the amount of exhaust gases that are trapped within the cylinder from a previous cycle or the amount of EGR supplied to the cylinder. Charge temperature may be used to vary torque by increasing or decreasing the expansion performed by the ignited gas and/or may be used to vary the timing of combustion in some modes, such as HCCI. As yet another example, fuel injection amount and/or timing can be used to vary the air/fuel ratio and the homogeneity of the mixture, thereby further varying the torque produced by the engine.
At 1620, it may be judged whether a sufficient reduction of torque the transients across the transition have been achieved. If the answer is yes, then the routine may return to 1610. Alternatively, if the answer at 1620 is no, it may be judged whether to enable increased transmission slip at 1622. As one example, increased transmission slip may be used where the torque transients across the transition are greater than a threshold. As another example, transmission slip may be used where one or more control parameters (e.g. 1614-1618) of the engine are at or near a limit. For example, the spark timing may be retarded only to a point where unstable combustion may occur, or fuel injection amount may be increased only to a certain extent. Further still, transmission slip may be avoided or reduced where fuel efficiency is desired as the use of transmission slip may serve to increase fuel consumption of the engine. In this way, transmission slip may be used to achieve reduced longitudinal acceleration and/or reduced excitation of the driveline under some conditions. Note that transmission slip may refer to slip provided by one or more clutches throughout the driveline between the engine and the drive wheel of the vehicle.
If the answer at 1622 is no, it may be judged at 1626 whether to continue to reduce torque transients via one or more operations described above with reference to 1614, 1616, and 1618. If the answer at 1626 is yes, one or more of 1614, 1616, and 1618 may be further adjusted to achieve the desired reduction of torque transients. Alternatively, if the answer at 1616 is no, the routine may return.
Alternatively, if the answer at 1622 is yes, a level of slip provided by one or more transmission clutches may be increased to achieve the desired torque transient reduction. In some conditions, the amount of slip may be based on the selected gear of the transmission or gear ratio. For example, when the transmission is set to a lower gear ratio, the amount of slip may be greater than when the transmission is set to a higher gear ratio in order to achieve a similar level of damping. Further still, excitation of the vehicle driveline may depend on the gear ratio of the transmission. As such, the extent to which operating conditions are varied in 1614, 1616, and 1618 may be based on the gear ratio of the transmission during the transition between combustion modes.
In some embodiments, the control system may vary the gear ratio of the transmission before, during, and/or after a transition of one or more cylinders between combustion modes in order to reduce excitation of the drive line. For example, a change in gear ratio may be performed with or without a corresponding increase in transmission slip, thereby enabling a reduction in torque transients caused by mode transitions. Finally, the routine may return to 1610 where operating conditions may be monitored for future transitions.
Note that the example control and estimation routines included herein can be used with various engine and/or vehicle system configurations. The specific routines described herein may represent one or more processing strategies such as event-driven, interrupt-driven, multi-tasking, multi-threading, and the like. As such, various steps, operations, or functions illustrated may be performed in the sequence illustrated, in parallel, or in some cases omitted. Likewise, the order of processing is not necessarily required to achieve the features and advantages of the example embodiments described herein, but is provided for ease of illustration and description. One or more of the illustrated steps or functions may be repeatedly performed depending on the particular strategy being used. Further, the described steps may graphically represent code to be programmed into the computer readable storage medium in the engine control system.
It will be appreciated that the configurations and routines disclosed herein are exemplary in nature, and that these specific embodiments are not to be considered in a limiting sense, because numerous variations are possible. For example, the above technology can be applied to V-6, I-4, I-6, V-12, opposed 4, and other engine types. The subject matter of the present disclosure includes all novel and nonobvious combinations and subcombinations of the various systems and configurations, and other features, functions, and/or properties disclosed herein.
The following claims particularly point out certain combinations and subcombinations regarded as novel and nonobvious. These claims may refer to “an” element or “a first” element or the equivalent thereof. Such claims should be understood to include incorporation of one or more such elements, neither requiring nor excluding two or more such elements. Other combinations and subcombinations of the disclosed features, functions, elements, and/or properties may be claimed through amendment of the present claims or through presentation of new claims in this or a related application. Such claims, whether broader, narrower, equal, or different in scope to the original claims, also are regarded as included within the subject matter of the present disclosure.
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