Gaseous injection quantity estimation and control using fourier transform methodology

Abstract

A process of operating a gaseous fueling system includes operating a plurality of gaseous fuel injector perform injections of gaseous fuel, measuring pressure of gaseous fuel supplied to the plurality of gaseous fuel injectors during the operating the plurality of gaseous fuel injector perform a plurality of injections of gaseous fuel, determining a set of Fourier transforms in response to the measuring, determining an average injection quantity for the plurality of gaseous fuel injectors in response to a first subset of the Fourier transforms, determining a plurality of disaggregated injection quantities for a plurality of subsets of the plurality of gaseous fuel injectors in response to a second subset of the Fourier transforms; and operating the gaseous fueling system using the disaggregated injection quantities.

Description

Attorney Docket No. CMI002-00114 GASEOUS INJECTION QUANTITY ESTIMATION AND CONTROL USING FOURIER TRANSFORM METHODOLOGY TECHNICAL FIELD

[0001] The present application relates to gaseous fueling systems controls and to gaseous injection quantity estimation and control using Fourier transform methodology and related apparatuses, controls, diagnostic, processes, systems, and techniques. BACKGROUND

[0002] Gaseous fueling systems for internal combustion engines and controls for such systems suffer from a number of shortcomings including those respecting accuracy, complexity, computational burden, dedicated hardware requirements, precision, reliability, and robustness, among other shortcomings. There remains a significant need for the unique apparatuses, processes, systems, and techniques disclosed herein. Page 1 of 40 130508684v1Attorney Docket No. CMI002-00114 DISCLOSURE OF EXAMPLE EMBODIMENTS

[0003] For the purposes of clearly, concisely, and exactly describing example embodiments of the present disclosure, the manner, and process of making and using the same, and to enable the practice, making and use of the same, reference will now be made to certain example embodiments, including those illustrated in the figures, and specific language will be used to describe the same. It shall nevertheless be understood that no limitation of the scope of the invention is thereby created, and that the invention includes and protects such alterations, modifications, and further applications of the example embodiments as would occur to one skilled in the art. SUMMARY OF THE DISCLOSURE

[0004] Some embodiments include unique gaseous fueling system controls. Further embodiments include unique apparatuses, systems, and processes comprising or embodying such controls. Further embodiments, forms, objects, features, advantages, aspects, and benefits shall become apparent from the following description and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0005] Fig.1 is a schematic diagram illustrating certain aspects of an example engine system including an example fueling system.

[0006] Fig.2 is a schematic diagram illustrating certain aspects of an example fueling system.

[0007] Figs.3A and 3B are a flow diagram illustrating certain aspects of an example process.

[0008] Figs.4A, 4B, and 4C are graphs illustrating certain aspects of example controls.

[0009] Fig.5 is a schematic diagram illustrating certain aspects of an example fueling system.

[0010] Figs.6A and 6B are a flow diagram illustrating certain aspects of an example process.

[0011] Figs.7A and 7B are graphs illustrating certain aspects of example controls

[0012] Figs.8A and 8B are graphs illustrating certain aspects of example controls.

[0013] Figs.9A, 9B, 9C, and 9D are graphs illustrating certain aspects of example controls.

[0014] Figs.10A-10F are graphs illustrating certain aspects of example controls.

[0015] Fig.11 is a flow diagram illustrating certain aspects of an example process.

[0016] Fig.12 is a schematic diagram illustrating certain aspects of example controls. Page 2 of 40 130508684v1Attorney Docket No. CMI002-00114 DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

[0017] With reference to Fig.1, there is illustrated a system 11 comprising an engine 10 and a gaseous fueling system 9. Gaseous fueling system 9 is configured to supply a gaseous fuel, such as such as natural gas, hydrogen, bio-derived gaseous fuels, hydrogen, mixed gases fuels or other gaseous fuels for combustion by engine 10. Engine 10 comprises combustion chambers 13 (also referred to as cylinders) of a reciprocating piston-in-cylinder-type engine which are configured to generate mechanical power from the combustion of gaseous fuel supplied by fuel injectors 12. Fuel injectors 12 are in fluid communication with respective combustion chambers 13 of the engine 10 and are structured to inject gaseous fuel which is provided to their respective combustion chambers 13.

[0018] In the illustrated embodiment, fuel injectors 12 are configured and provided in a multi- port injection (MPI) arrangement wherein each of fuel injectors 12 is configured to inject fuel into a respective port of intake manifold 37 leading to particular respective combustion chambers 13 of engine 10. It shall be appreciated that in MPI arrangements, each cylinder of a plurality of cylinders may be supplied with fuel individually by a dedicated injector (or a set of multiple dedicated injectors). Other embodiments may include other types and configurations of injectors.

[0019] Some embodiments comprise single point injection (SPI) arrangements wherein a plurality of fuel injectors are configured to inject fuel into a common intake system location leading to a plurality of combustion chambers up to and including all combustion chambers. It shall be appreciated that SPI arrangement may comprise multiple injectors which are configured to inject fuel at distinct loci of a common intake system location, are nevertheless sufficiently co- localized as to be considered to inject fuel at a single common point.

[0020] Some embodiments comprise direct injection (DI) arrangements wherein a plurality of fuel injectors are configured to inject fuel directly into respective combustion chambers of an engine. It shall be appreciated that in DI arrangements, each cylinder of a plurality of cylinders may be supplied with fuel individually by a dedicated injector (or a set of multiple dedicated injectors).

[0021] In the illustrated embodiment, four fuel injectors 12 and four combustion chambers 13 are depicted. It shall be appreciated that engine 10 may include fewer or greater numbers of fuel injectors 12 and combustion chambers 13. It shall be further appreciated that system 11 may be Page 3 of 40 130508684v1Attorney Docket No. CMI002-00114 provided in a number of forms including as a prime mover system (or component of a prime mover system) of vehicle, a genset, other power-load system.

[0022] In the illustrated embodiment, the gaseous fueling system 9 includes a gaseous fuel supply and injection system 17 and a gaseous fuel source system 32. Gaseous fuel supply and injection system 17 includes one or more rails 30 and one or more sets of injectors 12 operatively coupled with and supplied with gaseous fuel from a respective one of the one or more rails 30. The one or more rails 30 are, in turn, configured to receive pressurized fuel from gaseous fuel source system 32.

[0023] The gaseous fuel source system 32 may include a high pressure tank configured to store a supply of gaseous fuel at high pressure. In some embodiments, gaseous fuel source system 32 may include additional elements such as a compressor configured to compress gaseous fuel received from the fuel tank supply compressed gaseous fuel to the one or more rails 30, and / or and accumulator as well as electronically controllable valves configured to control supply of gaseous fuel to and from the accumulator and / or the one or more rails 30.

[0024] It shall be appreciated that the illustrated form of gaseous fueling system 9 is but one example of a fueling system according to the present disclosure. In other embodiments, the gaseous fueling system 9 may be configured and provided as another type of gaseous fueling system, for example, as a gaseous hydrogen fueling system. In other embodiments, gaseous fueling system 9 may be configured and provided in other forms, for example, as a high-pressure common-rail diesel fuel injection system or other types of fueling systems.

[0025] System 11 further includes electronic control system (ECS) 20 in communication with engine 10 and configured to control one or more aspects of engine 10, including controlling the injection of fuel into engine 10 via the fuel injectors 12. Accordingly, ECS 20 may be in communication with the fuel injectors 12 and configured to command each fuel injector 12 on and off at prescribed times to inject fuel into the engine 10 as desired. ECS 20 typically include at least one electronic control unit (ECU) 22 configured to execute operations of ECS 20 as described further herein and, in some embodiment, may include additional ECUs configured to execute operations of ECS 20 as described further herein.

[0026] ECS 20 may be further structured to control other parameters of engine 10, which may include aspects of engine 10 that may be controlled with an actuator activated by ECS 20. For Page 4 of 40 130508684v1Attorney Docket No. CMI002-00114 example, ECS 20 may be in communication with actuators and sensors for receiving and processing sensor input and transmitting actuator output signals. Actuators may include, but not be limited to, fuel injectors 12. The sensors may include any suitable devices to monitor operating parameters and functions of the system 11. For example, the sensors may include one or more pressure sensors 16 and one or more temperature sensors 18. The one or more pressure sensors 16 are in communication with the one or more rails 30 and structured to communicate a measurement of the pressure of gaseous fuel in the one or more rails 30 (also referred to as fuel rail pressure or rail pressure) to the ECS 20. The one or more temperature sensors 18 are in communication with the one or more rails 30 and structured to communicate a measurement of the temperature of gaseous fuel in the one or more rails 30 (also referred to as fuel rail temperature or rail temperature) to the ECS 20. System 11 include an intake manifold pressure (IMP) sensor 38 in communication with and configured to sense a pressure of intake manifold 37.

[0027] As will be appreciated by the description that follows, the techniques described herein relating to fuel injector or fuel injection parameters can be implemented in ECS 20, which may include one or more controllers for controlling different aspects of the system 11. In certain embodiments, the ECS 20 comprises one or more electronic control units (ECU) such as an engine control unit or engine control module. The ECS 20 may be comprised of digital circuitry, analog circuitry, or a hybrid combination of both of these types. Also, the ECS 20 may be programmable, an integrated state machine, or a hybrid combination thereof. The ECS 20 may include one or more Arithmetic Logic Units (ALUs), Central Processing Units (CPUs), memories, limiters, conditioners, filters, format converters, or the like which are not shown to preserve clarity. In one form, the ECS 20 is of a programmable variety that executes algorithms and processes data in accordance with operating logic that is defined by programming instructions (such as software or firmware). Alternatively or additionally, operating logic for the ECS 20 may be at least partially defined by hardwired logic or other hardware.

[0028] In addition to the types of sensors described herein, any other suitable sensors and their associated parameters may be encompassed by the system and methods. Accordingly, the sensors may include any suitable device used to sense any relevant physical parameters including electrical, mechanical, and chemical parameters of the engine system 11. As used herein, the term sensors may include any suitable hardware and / or software used to sense or estimate any engine system parameter and / or various combinations of such parameters either directly or indirectly. Page 5 of 40 130508684v1Attorney Docket No. CMI002-00114

[0029] With reference to Fig.2, there are illustrated further details of an example embodiment of gaseous fueling system 9. In the illustrated example of gaseous fueling system 9, gaseous fuel source system 32 is configured to supply pressurized gaseous fuel to front rail 30f and rear rail 30r. Front rail 30f and rear rail 30r are configured and provided as physically separated or divided gaseous fuel containment structures which may be provided in a number of forms including, for example, as physically separated or divided tubular fuel rails or pipes or physically separated or divided bores formed in an engine component such as an intake manifold or cylinder head. Front rail 30f and rear rail 30r preferably are supplied with pressurized gaseous fuel from gaseous fuel source system 32 at separate and distinct locations effective to provide a degree of isolation between their respective pressures.

[0030] Front rail 30f is configured and operable to supply pressurized gaseous fuel to a front plurality of injectors 12f which are configured to inject gaseous fuel to particular ones of a plurality of front cylinder intake ports 14f associated with a first plurality of cylinders 13f. In the illustrated example, the first plurality of cylinders 13f comprises the first, second, and third cylinders formed in a block of an in-line six-cylinder engine 10i. In the illustrated example, front plurality of injectors 12f comprises injectors 1A, 1B, 2A, 2B, 3A, and 3B. Injectors 1A and 1B are configured to supply gaseous fuel to a first intake port of intake manifold 37 leading to a first combustion cylinder. Injectors 2A and 2B are configured to supply gaseous fuel to a second intake port of intake manifold 37 leading to a second combustion cylinder. Injectors 3A and 3B are configured to supply gaseous fuel to a third intake port of intake manifold 37 leading to a third combustion cylinder.

[0031] Rear rail 30r is configured and operable to supply pressurized gaseous fuel to a rear plurality of injectors 12r which are configured to inject gaseous fuel to particular ones of a plurality of rear cylinder intake ports 14r associated with a second plurality of cylinders 13r. In the illustrated example, the second plurality of cylinders 13r comprises the fourth, fifth, and sixth cylinders formed in a block of an in-line six-cylinder engine 10i. In the illustrated example, rear plurality of injectors 12r comprises injectors 4A, 4B, 5A, 5B, 6A, and 6B. Injectors 4A and 4B are configured to supply gaseous fuel to a fourth intake port of intake manifold 37 leading to a fourth combustion cylinder. Injectors 5A and 5B are configured to supply gaseous fuel to a fifth intake port of intake manifold 37 leading to a fifth combustion cylinder. Injectors 6A and 6B are configured to supply gaseous fuel to a sixth intake port of intake manifold 37 leading to a sixth Page 6 of 40 130508684v1Attorney Docket No. CMI002-00114 combustion cylinder.

[0032] It shall be appreciated that front rail 30f and rear rail 30r are one example of a form in which the one or more rails 30 illustrated and described in connection with Fig.1 comprise a first rail and a second rail separated or divided from the first rail. Other embodiments in which the one or more rails 30 comprise a first rail and a second rail separated or divided from the first rail are also contemplated. Such embodiments include, for example, systems comprising relative arrangements and positionings of multiple fuel rails servicing a set of in-line cylinders other than front and rear, systems wherein the one or more rails 30 comprise three or more rails, and / or systems wherein the one or more rails 30 comprise two or more rails configured to supply gaseous fuel to the same set or group of cylinders. Likewise, while the illustrated example pertains to an engine including six cylinders, other embodiments relate to other engines including more or less than six cylinders.

[0033] With reference to Figs. 3A and 3B, there is illustrated an example process 300 for operating an electronic control system (e.g., ECS 20 or another electronic control system), in operative communication with a fueling system (e.g., gaseous fueling system 9 or another fueling system). Process 300 may be implemented in and performed by one or more components of an electronic control system such as one or more electronic control units (e.g., ECU 22 and / or other electronic control units) and / or by other electronic control system components.

[0034] Process 300 is configured for use with the front bank of a four stroke, six-cylinder engine and a split rail fuel system. A similar process methodology is used with the rear bank or with alternative engine and fuel system configurations. For a non-split rail with a six-cylinder engine, the engines ½ firing frequency harmonic is equal to the injector 3 / 3 frequency harmonic and included as one of the options in the individual injector injected quantity percent difference relative to the average injected quantity value.

[0035] Process 300 begins at start operation 302 and proceeds to operation 304 which measures pressure of gaseous fuel supplied to a plurality of injectors during operation of the plurality of gaseous fuel injector perform a plurality of injections of gaseous fuel. Operation 304 may measure and store the rail pressure data for a complete engine cycle (for example, 720 degrees @ 6 degrees samples = 120 data points).

[0036] It shall be appreciated that in the process 300 is configured for operation in connection with an MPI arrangement wherein the injection cycle (a repeating cycle in which all injectors have Page 7 of 40 130508684v1Attorney Docket No. CMI002-00114 operated to perform an injection, or have had had an injection event opportunity even if zero fueling was commanded) has the same fundamental frequency as the 720 degree engine cycle. Thus, the cylinder firing domain and the injector operation domain correspond to one another and can be thought of interchangeably for some purposes.

[0037] From operation 304, process 300 proceeds to operation 306 which determines a set of Fourier transforms in response to the pressure measurement of operation 302. Operation 306 may compute average pressure, ^^^௩^, and the discrete Fourier transforms (real ^^^^^ / ଷ^ி், ^^^^ଶ / ଷ^ி், ^^^^ଷ / ଷ^ி், ^^^^^ / ଷ^ி், ^^^^ଽ / ଷ^ி்; imaginary ^^^^^ / ଷ^ி், ^^^^ଶ / ଷ^ி், ^^^^ଷ / ଷ^ி், ^^^^^ / ଷ^ி், ^^^^ଽ / ଷ^ி்; magnitudes ^^^^^ / ଷ^ி், ^^^^ଶ / ଷ^ி், ^^^^ଷ / ଷ^ி், ^^^^^ / ଷ^ி், ^^^^ଽ / ଷ^ி்; and phases ^^^ / ଷ^ி், ^^ଶ / ଷ^ி், ^^ଷ / ଷ^ி், ^^^ / ଷ^ி், ^^ଽ / ଷ^ி்) for the 1 / 3, 2 / 3, 3 / 3, 6 / 3, and 9 / 3 injector operating order frequencies. It shall be appreciated that the 3 / 3 injector operating order frequency comprises the fundamental frequency, the 1 / 3 injector operating order frequency and the 2 / 3 injector operating order frequency comprise sub-harmonics of the fundamental frequency, and the 6 / 3 injector operating order frequency and the 9 / 3 injector operating order frequency comprise positive integer multiples of the fundamental frequency.

[0038] From operation 306, process 300 proceeds to operation 308 which determines an average injection quantity for the plurality of gaseous fuel injectors in response to a first subset of the Fourier transforms, for example, the 3 / 3 fundamental injector operating order frequency, the 6 / 3 injector operating order frequency and the 9 / 3 injector operating order frequency (or in principle additional positive integer multiples of the fundamental frequency). Operation 308 may, based on the fuel system configuration and the engine and fuel operating condition (engine speed and average rail pressure) calculate an estimate of the average injected quantity , ^^^௩^, for the cylinders associated with the measured rail pressure utilizing the average rail pressure ^^^௩^, the engine speed, and the control structure selected magnitude or magnitudes ^^^^ଷ / ଷ^ி், ^^^^^ / ଷ^ி்or the ^^^^ଽ / ଷ^ி், of the 1.0 (3 / 3), 1.0 (6 / 3) or the 3.0 (9 / 3) injector operating order frequency harmonics. Operation 308 may determines an average injection quantity (^^^௩^) using controls corresponding to one or more of graph 410 of Fig.4A, graph 420 of Fig.4B, and graph 430 of Fig. 4C.

[0039] From operation 308, process 300 proceeds to operation 310 which determines adjustment parameters to account for differences in the system relationship between a pressure Page 8 of 40 130508684v1Attorney Docket No. CMI002-00114 sensor and the plurality of injectors, for example, each injector may have different distance from a given pressure sensor and a different passage geometry along that distance. Operation 310 may calculate the phase offset ^^^ / ଷ^^^^^௧, ^^ଶ / ଷ^^^^^௧percentage injected quantity multipliers %^^^^^^^^^ / ଷ, %^^^^^^^^ଶ / ଷinjector percentage offset terms Δ%^^^^^^^௧ ^௬^ ^,Δ%^^^^^^^௧ ^௬^ ଶ,Δ%^^^^^^^௧ ^௬^ ଷ, and Δ%^^^^^^^and which account for the non-symmetry of the fuel system flow passage geometry and pressure sensor location using equations or tables based the engine speed, average rail pressure ^^^௩^, and average injected quantity, ^^^௩^.

[0040] From operation 310, process 300 proceeds to operation 320 which determines the percent injected quantity difference ^^%^^^௬^^^ௗ^^ ^;^^^^^^ ^^ௗ^^, ^ୀ^relative to the average injected quantity , ^^^௩^, for the cylinders associated with the measured rail pressure. For example, for a cylinder 1, cylinder 5 cylinder 3 firing order, operation 320 may calculate the percent injected quantity differences as: ^^%^^^௬^^^ௗ^^ ^;^^^^^^ ^^ௗ^^, ^ୀ^ ൌ ^^^^ భ ∗ %^^^^^^^^ భ ∗ cos ^^^^ െ 1^ഏ ^య^ ^^ భ ^ ^^ భ െ ^ ^ ∗measurement for each cylinder associated with the measured rail pressure, ^^^௬^^^ௗ^^ ^. Operation 322 may for example, determine fueling measurement for cylinder 1, cylinder 5, and cylinder 3 as: Page 9 of 40 130508684v1Attorney Docket No. CMI002-00114^^^௬^^^ௗ^^ ^ ൌ ^^^௩^ ∗ ^1 ^ ^Δ%^^ ^^^^^௧ ^௬^ ^ ^ Δ%^^ ^^^^^ ∗ ^ Δ%^^^௬^^^ௗ^^ ^:^^^^^^ ^^ௗ^^, ^ୀ^ / 100^^); / ଷ^^^^^௧ ^௬^ ଷ ^^^^^ ଷ:^^^^^^ ^^ௗ^^, ^ୀଷ / 100^^).

[0042] From operation 322, process 300 proceeds to operation 324 and may end or repeat, it being appreciated that in instances wherein process 300 ends it may be thereafter be repeated or reinitiated.

[0043] It shall be appreciated that operations 320 and 322 are example operations which may be utilized in connection with determining a plurality of disaggregated injection quantities for a plurality of subsets of the plurality of gaseous fuel injectors in response to a second subset of the Fourier transforms. It shall be further appreciated that the terms denoted with a “DFT” subscript in the example calculations described in connection with process 300 connote DFT values that are determined at run time, and that the other terms described are control features that are predetermined at run time and may be implemented, for example, as calibratible values.

[0044] With reference to Fig.4A-4C, there are illustrated graph 410, graph 420, and graph 430 which depict certain aspects of example controls which may be implemented in and executed by one or more components of an electronic control system such as one or more electronic control units and / or by other electronic control system components.

[0045] Graph 410 of Fig.4A depicts a set of curves from which injected fuel quantity may be determined as a function of DFT amplitude or magnitude for the 3 / 3 injector operating order frequency which corresponds to the fundamental frequency. Each of the illustrated set of curves corresponds to a different engine operating speed. Example controls according to Graph 410 may comprise a lookup table which receives input 411 comprising a determined DFT amplitude or magnitude and an engine speed, and determines and outputs a corresponding injected quantity 412 based on calibratible predetermined values corresponding to the illustrated curve for the indicated engine speed.

[0046] Graph 420 of Fig.4B depicts a set of curves from which injected fuel quantity may be determined as a function of DFT amplitude or magnitude for the 6 / 3 injector operating order Page 10 of 40 130508684v1Attorney Docket No. CMI002-00114 frequency which corresponds to the fundamental frequency. Each of the illustrated set of curves corresponds to a different engine operating speed. Example controls according to graph 420 may comprise a lookup table which receives input 421 comprising a determined DFT amplitude or magnitude and an engine speed, and determines and outputs an corresponding injected quantity 422 based on calibratible predetermined values corresponding to the illustrated curve for the indicated engine speed.

[0047] Graph 430 of Fig.4C depicts a set of curves from which injected fuel quantity may be determined as a function of DFT amplitude or magnitude for the 9 / 3 injector operating order frequency which corresponds to the fundamental frequency. Each of the illustrated set of curves corresponds to a different engine operating speed. Example controls according to Graph 430 may comprise a lookup table which receives input 431 comprising a determined DFT amplitude or magnitude and an engine speed, and determines and outputs a corresponding injected quantity 432 based on calibratible predetermined values corresponding to the illustrated curve for the indicated engine speed.

[0048] It shall be appreciated that example controls according to two or more of graph 410, graph 420, and graph 430 may determine an average, a weighted average, or other statistical parameter and utilize the determined value as the output an injected quantity. In some embodiments, controls corresponding to a single one of graph 410, graph 420, graph 430, or another graph of a positive integer multiple of the fundamental frequency may be utilized.

[0049] It shall be appreciated that the controls corresponding to and / or implementing the features illustrated and described in connection with graph 410, graph 420, and graph 430 may be implemented using lookup tables (LUT) as described above, by run-time calculations, estimations, and / or statistical techniques, or by a combination of these and other computational techniques as will occur to one of skill in the art. It shall be further appreciated that the other control determinations disclosed herein may likewise be implemented in any of the foregoing manners.

[0050] Controls according to graph 410, graph 420, and / or graph 430 are an example of controls which, based on the fuel system configuration and the engine and fuel operating condition (engine speed and average rail pressure), calculate an estimate of the average injected quantity , ^^_^^^^^^ , for the cylinders associated with the measured rail pressure utilizing the average rail pressure, ^^_^^^^^^, the engine speed, and the control structure selected magnitude or magnitudes ^^^^ଷ / ଷ^ி், ^^^^^ / ^^ி், ^^^^ଽ / ଷ^ி்,or ^^^^^ଶ / ଷ^ி்of the injector 3 / 3, 6 / 3, 9 / 3 or 12 / 3 Page 11 of 40 130508684v1Attorney Docket No. CMI002-00114 operating order frequency harmonics.

[0051] It shall be appreciated that Figs. 4A-4C illustrates examples of the relationships between the discrete Fourier transform magnitudes as a function of the engine speed and at an average rail pressure, ^^_^^^^^^. An estimate of the injected quantity can be obtained at each of the firing frequency harmonics. Alternatively, the firing frequency harmonics with the most robust and precise injected quantity estimate can be selected based on the magnitude of the local gain relationship between the DFT magnitude and the injected quantity. For example, for the representative system embodiment, at a relatively low engine speed of 715 rpm, the 6 / 3 injector operating order frequency harmonic has the highest gain and at a higher engine speed of 1787.5 rpm, the 3 / 3 injector operating order frequency harmonic has the highest gain, at injection quantities less than 60 mg and an engine speed of 1072.5, the 9 / 3 injector operating order frequency harmonic has the highest gain.

[0052] With reference to Fig.5, there are illustrated certain aspects of an example SPI gaseous fueling system 509. In the illustrated example, gaseous fuel supply 502 is configured to supply pressurized gaseous fuel to inlet rail 510 via filter 504 and line 506. Inlet rail 510 is configured to supply fuel to a plurality of fuel injectors 512. A pressure sensor 511 is configured to measure pressure of gasous fuel in inlet rail 510. In the illustrated example, the plurality of fuel injectors 512 comprise five fuel injectors, namely injector 512a, injector 512b, injector 512c, injector 512d, injector 512e, and injector 512f. In other embodiments the plurality of fuel injectors 512 may comprise a greater or lesser number of injectors.

[0053] The plurality of fuel injectors 512 are configured to inject gaseous fuel into outlet rail 520 which is, in turn supplied to intake manifold 530 via line 522. Intake manifold 530 is configured to supply gaseous fuel to a plurality of cylinders 514 via a plurality of ports 513. In the illustrated example, gaseous fueling system 509 is configured to supply fuel to six cylinders 514a, 514b, 514c, 514d, 514e, and 514f via six respective ports 513a, 513b, 513c, 513d, 513e, 513f. In other embodiments, different numbers of cylinders and respective ports may be supplied with gaseous fuel. Gaseous fueling system 509 is operatively coupled with an electronic control system (not depicted) which may be similar to ECS 20 described herein above.

[0054] With reference to Figs. 6A and 6B, there is illustrated an example process 600 for operating an electronic control system in operative communication with an SPI fueling system (e.g., SPI gaseous fueling system 509 or another SPI fueling system). Process 600 may be Page 12 of 40 130508684v1Attorney Docket No. CMI002-00114 implemented in and performed by one or more components of an electronic control system such as one or more electronic control units and / or by other electronic control system components.

[0055] Process 300 is configured for use with a single point injection (SPI) system of a four stroke, six-cylinder engine and a fuel system which consists of 5 injectors firing with a 120 crank degree start of injection command separation to the injectors which firing in a sequential order based on the injector number. The engine firing frequency harmonic is included in the individual injector injected quantity percent difference relative to the average injected quantity value.

[0056] It shall be appreciated that process 600 is configured for operation in connection with an SPI arrangement wherein the number of injectors is less than the number of cylinders, namely 5 SPI injectors are configured to supply fuel to 6 cylinders. Accordingly an injection cycle (a repeating cycle in which all injectors have operated to perform an injection, or have had had an injection event opportunity even if zero fueling was commanded) has a fundamental frequency of 600 degrees of engine cycle that is different from the fundamental frequency of the 720 degree engine cycle. Thus, the cylinder firing domain and the injector operation domain may not correspond to one another. It shall be appreciated that other SPI arrangements may have a number of injectors equal to the number of cylinders, for example, 6 SPI injectors configured to supply fuel to 6 cylinders. In such embodiments, the injection cycle will have the same fundamental frequency as the 720 degree engine cycle similar to process 300 for an MPI arrangement. It shall be further appreciated that process 600 provide an example of the discrete Fourier transform (DFT) based injected quantity estimation methodology with the single point injection system (SPI) consisting of a four stroke, six-cylinder engine and a fuel system which consists of 5 injectors firing with a 120 crank degree start of injection command separation to the injectors firing in a sequential order of injector number 1, 5, 2, 4 and 3. It shall be also beappreciated that other SPI arrangements may have a number of injectors more than the number of cylinders It shall also be appreciated that process 600 may also be configured for use with other types of gaseous fuel systems, for example, a DI system.

[0057] Process 600 begins at start operation 602 and proceeds to operation 604 which measures pressure of gaseous fuel supplied to a plurality of injectors during operation of the plurality of gaseous fuel injector perform a plurality of injections of gaseous fuel. Operation 604 may measure and store the rail pressure data for a complete injector cycle (for example: 600 degrees @ 6 degrees samples = 100 data points). Page 13 of 40 130508684v1Attorney Docket No. CMI002-00114

[0058] From operation 604, process 600 proceeds to operation 606 which determines a set of Fourier transforms in response to the pressure measurement of operation 302. Operation 606 may compute average pressure, ^^^௩^, and the discrete Fourier transforms (real ^^^^^ / ହ^ி், ^^^^ଶ / ହ^ி், ^^^^ଷ / ହ^ி், ^^^^ସ / ହ^ி், ^^^^ହ / ହ^ி்; imaginary ^^^^^ / ହ^ி், ^^^^ଶ / ହ^ி், ^^^^ଷ / ହ^ி், ^^^^ସ / ହ^ி், ^^^^ହ / ହ^ி்; magnitudes ^^^^^ / ହ^ி், ^^^^ଶ / ହ^ி், ^^^^ଷ / ହ^ி், ^^^^ସ / ହ^ி், ^^^^ହ / ହ^ி்; and phases ^^^ / ହ^ி், ^^ଶ / ହ^ி், ^^ଷ / ହ^ி், ^^ସ / ହ^ி், ^^ହ / ହ^ி்) for the 1 / 5, 2 / 5, 3 / 5, 4 / 5, and 5 / 5 injector operating order frequencies. It shall be appreciated that the 5.5 injector operating order frequency comprises the fundamental frequency, and the 1 / 5, 2 / 5, 3 / 5, and 4 / 5 injector operating order frequencies comprise sub- harmonics of the fundamental frequency.

[0059] From operation 606, process 600 proceeds to operation 608 which determines an average injection quantity for the plurality of gaseous fuel injectors in response to a first subset of the Fourier transforms, for example, the 5 / 5 fundamental injector operating order fundamental frequency and / or higher order positive integer harmonics thereof. Operation 308 may, based on the fuel system configuration and the engine and fuel operating condition (engine speed and average rail pressure) calculate an estimate of the average injected quantity , ^^^௩^, for the cylinders associated with the measured rail pressure utilizing the average rail pressure ^^^௩^, the engine speed, and the control structure selected magnitude ^^^^ହ / ହ^ி்and / or positive integer multiples thereof such as ^^^^^^ / ହ^ி், or other higher order injector operating order frequency harmonics. Operation 608 may determines an average injection quantity,^^^௩^using conrols corresponding to one or more of graph 810 of Fig.8A and graph 820 of Fig.8B.

[0060] The fundamental frequency (5 / 5) output response DFT sinusoidal component from the supply pressure signal which are associated with the average injector’s injected quantity is illustrated in graph 710 of Fig.7A. The harmonic frequency (10 / 5) output response DFT sinusoidal component from the supply pressure signal which are associated with the average injector’s injected quantity is illustrated in graph 720 of Fig.7B. In Figs.7A and 7B, the injector operating pulses are spaced apart. It shall be appreciated that process 600 may also be utilized in connection with partially overlapping injector pulses.

[0061] From operation 608, process 600 proceeds to operation 610 which determines adjustment parameters to account for differences in the system relationship between a pressure sensor and the plurality of injectors, for example, each injector may have different distance from Page 14 of 40 130508684v1Attorney Docket No. CMI002-00114 a given pressure sensor and a different passage geometry along that distance. Operation 610 may calculate the phase offset ^^^ / ହ^^^^^௧, ^^ଶ / ହ^^^^^௧, ^^ଷ / ହ^^^^^௧,^^ସ / ହ^^^^^௧percentage injected quantity multipliers %^^^^^^^^^ / ହ, %^^^^^^^^ଶ / ହ, %^^^^^^^^ଷ / ହ, %^^^^^^^^ସ / ହinjector percentage offset terms Δ%^^ ,Δ%^^^^^^^௧,^ୀଷ,Δ%^^^^^^^௧,^ୀସ, and Δ%^^^^^^^௧,^ୀହ, andΔ%^^^^^^^for the non-symmetry of the fuel system flow passage geometry and pressure sensor location using equations or tables based the engine speed, average rail pressure ^^^௩^, and average injected quantity, ^^^௩^.

[0062] From operation 610, process 600 proceeds to operation 620 which determines the percent injected quantity difference ^^%^^^௬^^^ௗ^^ ^;^^^^^^ ^^ௗ^^, ^ୀ^relative to the average injected quantity , ^^^௩^, for the cylinders associated with the measured rail pressure. For example, operation 620 may calculate the percent injected quantity differences as:^^%^^ ൌ ^^^^ ∗ %^^^^^^^^ ∗ cos ^ ^ഏ ^^^^^௧^^ ^^^^^௧^^^ ^^ௗ^^ୀ^ ^ / ହ^ி் ^ / ହ ^ ^^ െ 1ఱ^ ^^^ / ହ^ி் ^^fueling measurement for each cylinder associated with the measured rail pressure, ^^^௬^^^ௗ^^ ^. Operation 322 may for example, determine fueling measurement for injectors one through five as:^^^^^^^௧^^ ^^^^^௧^^^ ^^ௗ^^ୀ^ୀ^ ൌ ^^^௩^ ∗ ^1 ^ ^Δ%^^ ^^^^^௧,^ୀ^ ^ Δ%^^ ^^^^^ ∗130508684v1Attorney Docket No. CMI002-00114 ^Δ%^^^^^^^௧^^ ^^^^^௧^^^ ^^ௗ^^ୀ^ୀହ / 100^^).

[0064] From operation 622, process 600 proceeds to operation 624 and may end or repeat, it being appreciated that in instances wherein process 600 ends it may be thereafter be repeated or reinitiated.

[0065] It shall be appreciated that operations 620 and 622 are example operations which may be utilized in connection with determining a plurality of disaggregated injection quantities for a plurality of subsets of the plurality of gaseous fuel injectors in response to a second subset of the Fourier transforms. It shall be further appreciated that the terms denoted with a “DFT” subscript in the example calculations described in connection with process 600 connote DFT values that are determined at run time, and that the other terms described are control features that are predetermined at run time and may be implemented, for example, as calibratible values.

[0066] With reference to Fig.8A and 8B, there are illustrated graph 810 and graph 820 which depict certain aspects of example controls which may be implemented in and executed by one or more components of an electronic control system such as one or more electronic control units and / or by other electronic control system components.

[0067] Graph 810 of Fig.8A depicts a set of curves from which injected fuel quantity may be determined as a function of DFT amplitude or magnitude for the 5 / 5 injector operating order frequency which corresponds to the fundamental frequency. Each of the illustrated set of curves corresponds to a different engine operating speed. Example controls according to Graph 810 may comprise a lookup table which receives input 811 comprising a determined DFT amplitude or magnitude and an engine speed, and determines and outputs a corresponding injected quantity 812 based on calibratible predetermined values corresponding to the illustrated curve for the indicated engine speed.

[0068] Graph 820 of Fig.8B depicts a set of curves from which injected fuel quantity may be determined as a function of DFT amplitude or magnitude for the 10 / 5 injector operating order frequency which corresponds to the fundamental frequency. Each of the illustrated set of curves corresponds to a different engine operating speed. Example controls according to graph 820 may comprise a lookup table which receives input 821 comprising a determined DFT amplitude or magnitude and an engine speed, and determines and outputs an corresponding injected quantity 822 based on calibratible predetermined values corresponding to the illustrated curve for the indicated engine speed. Page 16 of 40 130508684v1Attorney Docket No. CMI002-00114

[0069] It shall be appreciated that example controls according to graph 810 and graph 820 may determine an average, a weighted average, or other statistical parameter and utilize the determined value as the output an injected quantity. In some embodiments, controls corresponding to a single one of graph 810, graph 820, or another graph of a positive integer multiple of the fundamental frequency may be utilized.

[0070] It shall be appreciated that the controls corresponding to and / or implementing the features illustrated and described in connection with graph 810 and graph 820 may be implemented using lookup tables (LUT) as described above, by run-time calculations, estimations, and / or statistical techniques, or by a combination of these and other computational techniques as will occur to one of skill in the art. It shall be further appreciated that the other control determinations disclosed herein may likewise be implemented in any of the foregoing manners.

[0071] Controls according to graph 810 and / or graph 820 are an example of controls which, based on the fuel system configuration and the engine and fuel operating condition (engine speed and average rail pressure), calculate an estimate of the average injected quantity , ^^_^^^^^^ , for the cylinders associated with the measured rail pressure utilizing the average rail pressure, ^^_^^^^^^, the engine speed, and the control structure selected magnitude or magnitudes magnitude or magnitudes ^^^^ହ / ହ^ி்or ^^^^^^ / ହ^ி்of the 5 / 5 or 10 / 5 firing order frequency harmonics..

[0072] It shall be appreciated that Figs. 8A and 8B illustrates examples of the relationships between the discrete Fourier transform magnitudes as a function of the engine speed and at an average rail pressure, ^^_^^^^^^. An estimate of the injected quantity can be obtained at each of the firing frequency harmonics. Alternatively, the firing frequency harmonics with the most robust and precise injected quantity estimate can be selected based on the magnitude of the local gain relationship between the DFT magnitude and the injected quantity.

[0073] With reference to Figs. 9A-9D, there are illustrated graphs 910, 920, 930, and 940 which illustrate examples of the relationships between the discrete Fourier transform magnitudes for an example embodiment system associated with example SPI gaseous fueling system 509 when operating at an engine speed of 1400 rpm and an average injected quantity for an individual injector of 122 mg for a gaseous fuel mixture at 35 C and a molecular weight of 18.07 grams per mole and the average injected quantity. As with all illustrative embodiments and methods depicted, the output DFT sinusoidal characteristics depend on factors such as the system layout and dimensional characteristics, the engine speed, the average rail pressure, the injected quantities, and the gaseous Page 17 of 40 130508684v1Attorney Docket No. CMI002-00114 fuel composition.

[0074] Graph 910 illustrates an output DFT sinusoid for the 1 / 5 harmonic term. Graph 920 illustrates an output DFT sinusoid for the 2 / 5 harmonic term. Graph 930 illustrates an output DFT sinusoid for the 3 / 5 harmonic term. Graph 940 illustrates an output DFT sinusoid for the 4 / 5 harmonic term, based on the fuel system configuration and the engine and fuel operating condition (engine speed and average rail pressure) an estimate of each individual injectors percent difference from the ^^_^^^^^^ , for the cylinders associated with the measured rail pressure can be calculated utilizing the average rail pressure, ^^_^^^^^^, the engine speed, and the control structure selected magnitudes and phases of all of the sub-harmonic terms. For the representative example configuration with 5 injectors, the magnitudes and phases used are: ^^^^^ / ହ^ி், ^^^^ଶ / ହ^ி், ^^^^ଷ / ହ^ி், ^^^^ସ / ହ^ி், ^^^ / ହ^ி், ^^ଶ / ହ^ி், ^^ଷ / ହ^ி், ^^ସ / ହ^ி்of the 1 / 5, 2 / 5, 3 / 5 and 4 / 5 firing order frequency harmonics.

[0075] With reference to Figs.10A-10F, there are illustrated graphs 1010, 1020, 1030, 1040, 1050, and 1060 which illustrate certain aspects of another embodiment of the controls disclosed herein. Controls according to graphs 1010, 1020, 1030, 1040, 1050, and 1060 may utilize aggregated sub-harmonic values which offers a lower computational burden relative to calculating individual injection quantities for each injector as described herein above. Variation in the sub- harmonic DFT sum waveforms may be utilized by example controls to identify over and under excursions of individual injectors.

[0076] Graph 1010 of Fig.10A illustrates a curve corresponding to the DFT sum of the 1 / 5, 2 / 5, 3 / 5, and 4 / 5 harmonic terms in conjunction with injector operation events for injector 1, injector 2, injector 3, injector 4, and injector 5. In the illustrated graph the amounts of each injection event are substantially equal with some variation within parameters deemed to reflect normal operation.

[0077] Graph 1020 of Fig.10B illustrates a curve corresponding to the DFT sum of the 1 / 5, 2 / 5, 3 / 5, and 4 / 5 harmonic terms in conjunction with injector operation events for injector 1, injector 2, injector 3, injector 4, and injector 5. In the illustrated graph the amounts of each injection event may still be considered nearly equal but for which injector 5 operation exhibits some overage and injector 3 operation exhibits some underage with resulting inverse excursions of the DFT sum waveform as illustrated by the lowest negative value of the DFT sum waveform associated with injector 5 operation and the highest DFT sum waveform associated with injector 3 operation. Page 18 of 40 130508684v1Attorney Docket No. CMI002-00114

[0078] Graph 1030 of Fig.10C illustrates a curve corresponding to the DFT sum of the 1 / 5, 2 / 5, 3 / 5, and 4 / 5 harmonic terms in conjunction with injector operation events for injector 1, injector 2, injector 3, injector 4, and injector 5. In the illustrated graph the amounts of each injection event may still be considered nearly equal but for which injector 5 operation exhibits some overage and injector 2 operation exhibits some underage with resulting inverse excursions of the DFT sum waveform as illustrated by the lowest negative value of the DFT sum waveform associated with injector 2 operation and the highest DFT sum waveform associated with injector 5 operation.

[0079] Graph 1040 of Fig.10D illustrates a curve corresponding to the DFT sum of the 1 / 5, 2 / 5, 3 / 5, and 4 / 5 harmonic terms in conjunction with injector operation events for injector 1, injector 2, injector 3, injector 4, and injector 5. In the illustrated graph the amounts of each injection event may still be considered nearly equal but for which injector 1 operation exhibits some overage and injector 4 operation exhibits some underage with resulting inverse excursions of the DFT sum waveform as illustrated by the lowest negative value of the DFT sum waveform associated with injector 1 operation and the highest DFT sum waveform associated with injector 4 operation.

[0080] Graph 1050 of Fig. 10E illustrates a curve corresponding to the DFT sum of the 1 / 5, 2 / 5, 3 / 5, and 4 / 5 harmonic terms in conjunction with injector operation events for injector 1, injector 2, injector 3, injector 4, and injector 5. In the illustrated graph the amounts of each injection event may still be considered nearly equal but for which injector 4 operation exhibits some overage and injector 2 operation exhibits some underage with resulting inverse excursions of the DFT sum waveform as illustrated by the lowest negative value of the DFT sum waveform associated with injector 4 operation and the highest DFT sum waveform associated with injector 2 operation.

[0081] Graph 1060 of Fig. 10F illustrates a curve corresponding to the DFT sum of the 1 / 5, 2 / 5, 3 / 5, and 4 / 5 harmonic terms in conjunction with injector operation events for injector 1, injector 2, injector 3, injector 4, and injector 5. In the illustrated graph the amounts of each injection event may still be considered nearly equal but for which injector 1 operation exhibits some overage and injector 3 operation exhibits some underage with resulting inverse excursions of the DFT sum waveform as illustrated by the lowest negative value of the DFT sum waveform associated with injector 5 operation and the highest DFT sum waveform associated with injector 1 operation.

[0082] With reference to Fig.11, there is illustrated an example process 700 for operating an electronic control system in operative communication with a gaseous fueling system. Process 700 may be implemented in and performed by one or more components of an electronic control system Page 19 of 40 130508684v1Attorney Docket No. CMI002-00114 such as one or more electronic control units and / or by other electronic control system components.

[0083] Process 700 is configured for use with an SPI system of a four stroke, six-cylinder engine and a fuel system which consists of 5 injectors firing with a 120 crank degree start of injection command separation to the injectors which firing in a sequential order based on the injector number. The engine firing frequency harmonic is included in the individual injector injected quantity percent difference relative to the average injected quantity value. It shall be appreciated that process 700 may also be configured for use with other types of gaseous fuel systems, for example, an MPI system or a DI system.

[0084] Process 700 begins at start operation 702 and proceeds to operation 704 which measures pressure of gaseous fuel supplied to a plurality of injectors during operation of the plurality of gaseous fuel injector perform a plurality of injections of gaseous fuel. Operation 704 may measure and store the rail pressure data for a complete injector cycle (for example: 600 degrees @ 6 degrees samples = 100 data points).

[0085] From operation 704, process 700 proceeds to operation 706 which determines a set of Fourier transforms in response to the pressure measurement of operation 302. Operation 706 may compute average pressure, ^^^௩^, and the discrete Fourier transforms (real ^^^^^ / ହ^ி், ^^^^ଶ / ହ^ி், ^^^^ଷ / ହ^ி், ^^^^ସ / ହ^ி்; imaginary ^^^^^ / ହ^ி், ^^^^ଶ / ହ^ி், ^^^^ଷ / ହ^ி்,magnitudes ^^^^^ / ହ^ி், ^^^^ଶ / ହ^ி், ^^^^ଷ / ହ^ி்,^^^ / ହ^ி், ^^ଶ / ହ^ி், ^^ଷ / ହ^ி், ^^ସ / ହ^ி்) for the 1 / 5, 2 / 5, 3 / 5, and 4 / 5 injector operating order sub-harmonic frequencies.

[0086] From operation 706, process 700 proceeds to operation 708 which calculates the sum of the sinusoidal waveforms using discrete Fourier transforms amplitudes and phases for the1 / 5, 2 / 5, 3 / 5, and 4 / 5 injector operating order sub-harmonic frequencies.

[0087] From operation 708, process 700 proceeds to operation 717 which utilizes a relationship between the injection event position for an injector and the corresponding local DFT sub-harmonic sum relative value to estimate the relative injected quantity differences between the injectors.

[0088] From operation 708, process 700 also proceeds to operation 712 which, optionally, based on the fuel system configuration and the engine and fuel operating condition (engine speed and average rail pressure) calculate the expected sum of the sinusoidal waveforms using discrete Fourier transforms amplitudes and phases for the 1 / 5, 2 / 5, 3 / 5, and 4 / 5 injector operating order sub-harmonic frequencies which account for the non-symmetry of the fuel system flow passage Page 20 of 40 130508684v1Attorney Docket No. CMI002-00114 geometry and pressure sensor location using equations or tables based the engine speed, average rail pressure ^^^௩^, and average injected quantity, ^^^௩^.

[0089] From operation 712, process 700 proceeds to operation 714 which subtracts the measured sum of the DFT sub-harmonic terms from the expected DFT sum of sub-harmonic terms.

[0090] From operation 714, process 700 proceeds to operation 716 which utilizes a relationship between the injection event position for an injector and the corresponding local DFT sub-harmonic sum relative value to estimate the relative injected quantity differences between the injectors.

[0091] From operation 716 and operation 717, process 700 proceeds to operation 718 which balances the injection quantities by adjusting the commanded on-times for injectors. When injector has an injection quantity less than that of the average of the injectors (for example injector 3 in Fig.10B, injector 5 in Fig.10C, injector 4 in Fig.10D, injector 2 in Fig.10E, or injector 1 in Fig. 10F) there is a local maximum positive value in the sum of the sinusoidal waveforms of the discrete Fourier transform results of the sub-harmonic frequencies. When an injector has an injection quantity greater than that of the average of the injectors (for example injector 5 in Fig.10B, injector 2 in Fig. 10C, injector 1 in Fig. 10D, injector 4 in Fig. 10E, or injector 3 in Fig. 10F) there is a local maximum negative value in the sum of the sinusoidal waveforms of the discrete Fourier transform results of the sub-harmonic frequencies. The injection quantities can be balanced by adjusting the commanded on-times for injectors utilizing a relationship between the injection event position for an injector and the corresponding local DFT sub-harmonic sum relative value to estimate the relative injected quantity differences between the injectors.

[0092] From operation 718, process 700 proceeds to operation 719 and may end or repeat, it being appreciated that in instances wherein process 700 ends it may be thereafter be repeated or reinitiated.

[0093] With reference to Fig. 12, there are illustrated example controls 200 which may be implemented in and operated by one or electronic control units or other components of an electronic control system. Controls 200 include injector controls 210 which are configured to determine and output at least one injector control signal 219 to control operation of an injector 12i in response to one or more inputs. In the illustrated example, injector controls 210 are configured to determine and output injector commands for a particular individual injector 12i. Controls 200 may include additional instances of injector controls the same as or similar to injector controls 210 Page 21 of 40 130508684v1Attorney Docket No. CMI002-00114 which are configured to determine and output injector commands for other particular individual injectors.

[0094] In the illustrated example, injector controls 210 are configured to receive a plurality of inputs including fueling command 202, engine speed 203, and intake manifold pressure (IMP) 204, rail pressure 206, and rail temperature 208. In other embodiments, injector controls 210 may be configured to receive additional or alternative inputs.

[0095] Fueling command 202 may include a fueling quantity (Q) and a fueling pressure (P). Fueling command 202 may be determined and provided to injector controls 210 in response to an operator input such as an accelerator pedal position or in response to automated operation of an electronic control system such as an adaptive cruise control system. Engine speed 203 may be provided by an engine speed sensor. Engine speed 203 may be provided to injector controls 210 via a dedicated connection or via one or more communication networks.

[0096] IMP 204 may be provided by pressure sensor 38 which is in operative communication with and configured to sense a pressure of intake manifold 37. IMP 204 may be provided to injector controls 210 via a dedicated connection or via one or more communication networks.

[0097] Rail pressure 206 may be provided by pressure sensor 16 which is in operative communication with and configured to sense a pressure of fuel rail 20 which is configured to supply fuel to injector 12i and may also be configured to supply fuel to other injectors. Rail pressure 206 may be provided to injector controls 210 via a dedicated connection or via one or more communication networks.

[0098] Rail temperature 208 may be provided by temperature sensor 18 which is in operative communication with and configured to sense a temperature of fuel rail 20. Rail temperature 208 may be provided to injector controls 210 via a dedicated connection or via one or more communication networks.

[0099] Injector controls 210 comprise control circuitry configured to implement and execute control logic for processing the inputs received by injector controls 210 and to determine and output injector control signal 219. In the illustrated example the circuitry of injector controls 210 is configured to provide and execute pressure measurement processing logic 212, injection quantity estimation logic 214, injection control logic 216, and injection control modification logic 218. In other embodiments, the control logic provided by injector controls 210 may be differently organized with the aspects of one or more of the illustrated logic blocks being combined in a single Page 22 of 40 130508684v1Attorney Docket No. CMI002-00114 block or units, divided into multiple blocks or units, and / or provided with additional or alternative blocks or units.

[0100] In the illustrated example, pressure measurement processing logic 212 and injection quantity estimation logic 214 are configured to implement and execute one or more operations of a process. Pressure measurement processing logic 212 is configured to perform a plurality of operations relating to the receipt and processing of a rail pressure 206. Injection quantity estimation logic 214 is configured to perform a plurality of operations relating to calculation of an injected fuel quantity estimate using the output of pressure measurement processing logic 212. In other embodiments, the foregoing operations may be differently distributed between or among pressure measurement processing logic 212, injection quantity estimation logic 214, and / or additional logic injector controls 210.

[0101] Injection control logic 216, is configured to determine injector commands to provide output including injector control signal 219. Injector control logic 216 may be configured to determine an injector on-time command effective to set injector control signal 219 to an injector- on state or value for a duration corresponding to a commanded injector on time. Injector control logic 216 may determine the injector on-time command in response to fueling command 202, engine speed 203, and intake manifold pressure (IMP) 204, rail pressure 206, and rail temperature 208 and may utilize a number of techniques to perform this determination.

[0102] In some embodiments, injector control logic 216 may be configured and provided as one or more lookup tables, maps or response surfaces which are configured and operable to provide an injector on-time command in response to the aforementioned inputs.

[0103] In some embodiments, injector control logic 216 may be configured and operable to solve one or more equations to determine an injector on-time command in response to the aforementioned inputs. Equation (1) provides an example of an equation which may be so utilized: మమ^^ ൌொ^ ^^^ି^బା^భ^ೞା^మ^^ା^య^ೞା^ర^^ା^ఱ^ೞ^^(1) Wherein ^^at a defined reference temperature, ^^^is the pressure of gaseous at the fuel rail, ^^ௗis the intake manifold pressure, and^^^, ^^^, ^^ଶ, ^^ଷ, ^^ସ, ^^ହ, ^^^, ^^^^^^ ^^^ are coefficients which may be empirically determined or derivedfrom a physics based model and which may be tuned to vary the effect of equation (1).

[0104] The injector-on state of injector control signal 219 may be effective to actuate switch Page 23 of 40 130508684v1Attorney Docket No. CMI002-00114 234. Switch 234 is operatively coupled with a system voltage source (V_supply) and configured to selectably supply an injector current (I_inj) a solenoid 124 of an injector 12. The injector current (I_inj) is effective to energize solenoid 124 to induce lifting motion of injector armature 122 (sometimes referred to as an injector needle) in the direction generally indicated by arrow L. In the lifted position (illustrated in phantom as denoted by dashed lines), injector armature 122 allows fuel supplied to injector gallery 126 to exit one or more apertures of a tip of injector 12 as an fuel injection (F_inj) into a port of intake manifold 27 leading to an associated combustion chamber of engine 10.

[0105] Injection control modification logic 218 is configured to modify a relationship between an injector on-time command and a commanded injection quantity which is utilized by injector control logic 216 as described above. In some embodiment injection control modification logic 218 may be configured to modify one or more tables defining one or more relationships between commanded on-time as a function of injection quantity at a given gaseous fuel temperature and a given engine speed such as described above in connection with injector control logic 216. In some embodiment injection control modification logic 218 may be configured to modify one or more coefficients of an equation defining one or more relationships between commanded on-time as a function of injection quantity at a given gaseous fuel temperature and a given engine speed such as described above in connection with injector control logic 216. In some embodiments injection control modification logic 218 may be configured to modify one values in adaptive tables defining one or more relationships between commanded on-time as a function of injection quantity at a given gaseous fuel temperature and a given engine speed such as described above in connection with injector control logic 216.

[0106] Injection control modification logic 218 may modify one or more of the foregoing relationships between an injector on-time command and a commanded injection quantity by comparing a calculated injected fuel quantity estimate. The existing model of the relationship may comprise a set of look-up tables.

[0107] As shown by this detailed description, the present disclosure contemplates multiple and various embodiments, including, without limitation, the following example embodiments.

[0108] A first example embodiment is a process of operating a gaseous fueling system including a plurality of gaseous fuel injectors in fluid communication with a plurality of combustion cylinders, the process comprising: operating the plurality of gaseous fuel injector Page 24 of 40 130508684v1Attorney Docket No. CMI002-00114 perform injections of gaseous fuel; measuring pressure of gaseous fuel supplied to the plurality of gaseous fuel injectors during the operating the plurality of gaseous fuel injector perform a plurality of injections of gaseous fuel; determining a set of Fourier transforms in response to the measuring; determining an average injection quantity for the plurality of gaseous fuel injectors in response to a first subset of the Fourier transforms; determining a plurality of disaggregated injection quantities for a plurality of subsets of the plurality of gaseous fuel injectors in response to a second subset of the Fourier transforms; and operating the gaseous fueling system using the disaggregated injection quantities.

[0109] A second example embodiment includes the features of the first example embodiment, wherein the first subset of the Fourier transforms comprise one or more Fourier transforms taken at respective positive integer multiples of a fundamental frequency of operation of the plurality of gaseous fuel injectors.

[0110] A third example embodiment includes the features of the second example embodiment, wherein the first subset of the Fourier transforms comprise a first Fourier transforms taken a first positive integer multiple of the fundamental frequency and a second Fourier transforms taken a second positive integer multiple of the fundamental frequency.

[0111] A fourth example embodiment includes the features of the first example embodiment, wherein the second subset of the Fourier transforms comprises a set of sub-harmonics of a fundamental frequency of operation of the plurality of gaseous fuel injectors.

[0112] A fifth example embodiment includes the features of the fourth example embodiment, wherein the set of sub-harmonics comprises sub-harmonics for each fraction of a total number of injector firing events for the over the fundamental frequency.

[0113] A sixth example embodiment includes the features of the first example embodiment, wherein the gaseous fueling system is configured as a single point injection (SPI) system wherein the plurality of gaseous fuel injectors are configured to inject gaseous fuel at respective locations effective to supply fuel to any of the plurality of combustion cylinders.

[0114] A seventh example embodiment includes the features of the sixth example embodiment, wherein a total number of the plurality of gaseous fuel injectors is one of less than and greater than a total number of the plurality of combustion cylinders and a fundamental frequency of operation of the plurality of gaseous fuel injectors is lower than a fundamental frequency of operation of the combustion cylinders. Page 25 of 40 130508684v1Attorney Docket No. CMI002-00114

[0115] An eighth example embodiment includes the features of the first example embodiment, wherein the gaseous fueling system is configured as a multiple port injection (MPI) system, wherein a plurality of subsets of the plurality of gaseous fuel injectors are configured to inject gaseous fuel at respective locations effective to supply fuel individually to respective ones of the plurality of combustion cylinders.

[0116] A ninth example embodiment includes the features of the eighth example embodiment, wherein the plurality of subsets each comprise multiple injectors.

[0117] A tenth example embodiment includes the features of the eighth example embodiment, wherein and a fundamental frequency of operation of the plurality of gaseous fuel injectors is equal to a fundamental frequency of operation of the combustion cylinders.

[0118] An eleventh example embodiment includes the features of the first example embodiment, wherein the operating the gaseous fueling system using the disaggregated injection quantities comprises modifying injector control logic using the disaggregated injection quantities and controlling the gaseous fuel injector using the modified injector control logic.

[0119] A twelfth example embodiment includes the features of the first example embodiment, wherein the operating the gaseous fueling system using the disaggregated injection quantities comprises performing a diagnostic of the gaseous fuel injector using the disaggregated injection quantities.

[0120] A thirteenth example, embodiment is a system comprising: an electronic control system in operative communication with a gaseous fueling system including a plurality of gaseous fuel injectors in fluid communication with a plurality of combustion cylinders the electronic control system being configured to: operate the plurality of gaseous fuel injector perform injections of gaseous fuel; measure pressure of gaseous fuel supplied to the plurality of gaseous fuel injectors during operation of the plurality of gaseous fuel injector perform a plurality of injections of gaseous fuel; determine a set of Fourier transforms in response to the pressure measurement; determine an average injection quantity for the plurality of gaseous fuel injectors in response to a first subset of the Fourier transforms; determine a plurality of disaggregated injection quantities for a plurality of subsets of the plurality of gaseous fuel injectors in response to a second subset of the Fourier transforms; and operate the gaseous fueling system using the disaggregated injection quantities.

[0121] A fourteenth example embodiment includes the features of the thirteenth example Page 26 of 40 130508684v1Attorney Docket No. CMI002-00114 embodiment, wherein the first subset of the Fourier transforms comprise one or more Fourier transforms taken at respective positive integer multiples of a fundamental frequency of operation of the plurality of gaseous fuel injectors.

[0122] A fifteenth example embodiment includes the features of the fourteenth example embodiment, wherein the first subset of the Fourier transforms comprise a first Fourier transforms taken a first positive integer multiple of the fundamental frequency and a second Fourier transforms taken a second positive integer multiple of the fundamental frequency.

[0123] A sixteenth example embodiment includes the features of the thirteenth example embodiment, wherein the second subset of the Fourier transforms comprises a set of sub- harmonics of a fundamental frequency of operation of the plurality of gaseous fuel injectors.

[0124] A seventeenth example embodiment includes the features of the sixteenth example embodiment, wherein the set of sub-harmonics comprises sub-harmonics for each fraction of a total number of injector firing events for the over the fundamental frequency.

[0125] An eighteenth example embodiment includes the features of the thirteenth example embodiment, wherein the gaseous fueling system is configured as a single point injection (SPI) system wherein the plurality of gaseous fuel injectors are configured to inject gaseous fuel at respective locations effective to supply fuel to any of the plurality of combustion cylinders.

[0126] A ninteenth example embodiment includes the features of the eighteenth example embodiment, wherein a total number of the plurality of gaseous fuel injectors is less than a total number of the plurality of combustion cylinders and a fundamental frequency of operation of the plurality of gaseous fuel injectors is lower than a fundamental frequency of operation of the combustion cylinders.

[0127] A twentieth example embodiment includes the features of the thirteenth example embodiment, wherein the gaseous fueling system is configured as a multiple port injection (MPI) system, wherein a plurality of subsets of the plurality of gaseous fuel injectors are configured to inject gaseous fuel at respective locations effective to supply fuel individually to respective ones of the plurality of combustion cylinders.

[0128] A twenty-first example embodiment includes the features of the twentieth example embodiment, wherein the plurality of subsets each comprise multiple injectors.

[0129] A twenty-second example embodiment includes the features of the twentieth example embodiment, wherein and a fundamental frequency of operation of the plurality of gaseous fuel Page 27 of 40 130508684v1Attorney Docket No. CMI002-00114 injectors is equal to a fundamental frequency of operation of the combustion cylinders.

[0130] A twenty-third example embodiment includes the features of the thirteenth example embodiment, wherein the electronic control system is configured to operate the gaseous fueling system using the disaggregated injection quantities comprises modifying injector control logic using the disaggregated injection quantities and controlling the gaseous fuel injector using the modified injector control logic.

[0131] A twenty-fourth example embodiment includes the features of the thirteenth example embodiment, wherein the electronic control system is configured to operate the gaseous fueling system using the disaggregated injection quantities comprises performing a diagnostic of the gaseous fuel injector using the disaggregated injection quantities.

[0132] A twenty-fifth example embodiment is a process of operating a gaseous fueling system including a plurality of gaseous fuel injectors in fluid communication with a plurality of combustion cylinders, the process comprising: operating the plurality of gaseous fuel injectors to perform injections of gaseous fuel; measuring pressure of gaseous fuel supplied to the plurality of gaseous fuel injectors during the operating the plurality of gaseous fuel injector perform a plurality of injections of gaseous fuel; determining a set of Fourier transforms for a plurality of sub- harmonic frequencies in response to the measuring; determining a sum of sinusoidal waveforms in response to the set of Fourier transforms; determining relative injected quantity differences between the plurality of gaseous fuel injectors in response to the sum of sinusoidal waveforms; and operating the gaseous fueling system in response to the relative injected quantity differences.

[0133] A twenty-sixth example embodiment includes the features of the twenty-fifth example embodiment, wherein the determining the set of Fourier transforms comprises determining an average gaseous fuel pressure of the operating and determining the set of Fourier transforms in response to the average gaseous fuel pressure.

[0134] A twenty-seventh example embodiment includes the features of the twenty-fifth example embodiment, wherein the sum of sinusoidal waveforms is determined in response to amplitudes and phases of the plurality of sub-harmonic frequencies.

[0135] A twenty-eighth example embodiment includes the features of the twenty-fifth example embodiment, wherein the determining relative injected quantity differences between the injectors is further in response to a relationship between injection event positions for the plurality of gaseous fuel injectors and corresponding local values of the sum of sinusoidal waveforms. Page 28 of 40 130508684v1Attorney Docket No. CMI002-00114

[0136] A twenty-ninth example embodiment includes the features of the twenty-fifth example embodiment, comprising: calculating an expected sum of the sinusoidal waveforms accounting for non-symmetry of flow passage geometry and pressure sensor location of the gaseous fueling system; determining a difference of the sum of sinusoidal waveforms and the expected sum of sinusoidal waveforms; and determining relative injected quantity in response to the difference and a relationship between injection event position for an injector and a relationship between injection event positions for the plurality of gaseous fuel injectors and corresponding local values of the sum of sinusoidal waveforms.

[0137] A thirtieth example embodiment includes the features of the twenty-fifth example embodiment, wherein the operating the gaseous fueling system in response to the relative injected quantity differences comprises balancing injection quantities among the plurality of gaseous fuel injectors by adjusting commanded on-times for one or more of the plurality of gaseous fuel injectors.

[0138] A thirty-first example embodiment is a system comprising: an electronic control system in operative communication with a gaseous fueling system including a plurality of gaseous fuel injectors in fluid communication with a plurality of combustion cylinders the electronic control system being configured to: operate the plurality of gaseous fuel injectors to perform injections of gaseous fuel; measure pressure of gaseous fuel supplied to the plurality of gaseous fuel injectors during the operating the plurality of gaseous fuel injector perform a plurality of injections of gaseous fuel; determine a set of Fourier transforms for a plurality of sub-harmonic frequencies in response to the pressure measurement; determine a sum of sinusoidal waveforms in response to the set of Fourier transforms; determine relative injected quantity differences between the plurality of gaseous fuel injectors in response to the sum of sinusoidal waveforms; and operate the gaseous fueling system in response to the relative injected quantity differences.

[0139] A thirty-second example embodiment includes the features of the thirty-first example embodiment, wherein the electronic control system being configured to determine the set of Fourier transforms comprises the electronic control system being configured to determine an average gaseous fuel pressure of the operating and determine the set of Fourier transforms in response to the average gaseous fuel pressure.

[0140] A thirty-third example embodiment includes the features of the thirty-first example embodiment, wherein the sum of sinusoidal waveforms is determined in response to amplitudes Page 29 of 40 130508684v1Attorney Docket No. CMI002-00114 and phases of the plurality of sub-harmonic frequencies.

[0141] A thirty-fourth example embodiment includes the features of the thirty-first example embodiment, wherein the electronic control system is configured to determine relative injected quantity differences between the injectors further in response to a relationship between injection event positions for the plurality of gaseous fuel injectors and corresponding local values of the sum of sinusoidal waveforms.

[0142] A thirty-fifth example embodiment includes the features of the thirty-first example embodiment, wherein the electronic control system is configured to: calculate an expected sum of the sinusoidal waveforms accounting for non-symmetry of flow passage geometry and pressure sensor location of the gaseous fueling system; determine a difference of the sum of sinusoidal waveforms and the expected sum of sinusoidal waveforms; and determine relative injected quantity in response to the difference and a relationship between injection event position for an injector and a relationship between injection event positions for the plurality of gaseous fuel injectors and corresponding local values of the sum of sinusoidal waveforms.

[0143] A thirty-sixth example embodiment includes the features of the thirty-first example embodiment, wherein the electronic control system being configured to operate the gaseous fueling system comprises the electronic control system being configured to balance injection quantities among the plurality of gaseous fuel injectors by adjusting commanded on-times for one or more of the plurality of gaseous fuel injectors.

[0144] It shall be appreciated that terms such as “a non-transitory memory,” “a non-transitory memory medium,” and “a non-transitory memory device” refer to a number of types of devices and storage mediums which may be configured to store information, such as data or instructions, readable or executable by a processor or other components of a computer system and that such terms include and encompass a single or unitary device or medium storing such information, multiple devices or media across or among which respective portions of such information are stored, and multiple devices or media across or among which multiple copies of such information are stored.

[0145] It shall be appreciated that terms such as “determine,” “determined,” “determining” and the like when utilized in connection with a control method or process, an electronic control system or controller, electronic controls, or components or operations of the foregoing refer inclusively to any of a number of acts, configurations, devices, operations, and techniques, Page 30 of 40 130508684v1Attorney Docket No. CMI002-00114 individually or in combination, including, without limitation, calculation or computation of a parameter or value, obtaining a parameter or value from a lookup table or using a lookup operation, receiving parameters or values from a datalink or network communication, receiving an electronic signal (e.g., a voltage, frequency, current, or pulse-width modulation (PWM) signal) indicative of the parameter or value, receiving output of a sensor indicative of the parameter or value, receiving other outputs or inputs indicative of the parameter or value, reading the parameter or value from a memory location on a computer-readable medium, receiving the parameter or value as a run-time parameter, and / or by receiving a parameter or value by which the interpreted parameter can be calculated, and / or by referencing a default value that is interpreted to be the parameter value.

[0146] While example embodiments of the disclosure have been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only certain example embodiments have been shown and described and that all changes and modifications that come within the spirit of the claimed inventions are desired to be protected. It should be understood that while the use of words such as preferable, preferably, preferred or more preferred utilized in the description above indicates that the feature so described may be more desirable, it nonetheless may not be necessary and embodiments lacking the same may be contemplated as within the scope of the invention, the scope being defined by the claims that follow. In reading the claims, it is intended that when words such as “a,” “an,” “at least one,” or “at least one portion” are used there is no intention to limit the claim to only one item unless specifically stated to the contrary in the claim. When the language “at least a portion” and / or “a portion” is used the item can include a portion and / or the entire item unless specifically stated to the contrary. Page 31 of 40 130508684v1

Claims

Attorney Docket No. CMI002-00114 CLAIMS 1. A process of operating a gaseous fueling system including a plurality of gaseous fuel injectors in fluid communication with a plurality of combustion cylinders, the process comprising: operating the plurality of gaseous fuel injector perform injections of gaseous fuel; measuring pressure of gaseous fuel supplied to the plurality of gaseous fuel injectors during the operating the plurality of gaseous fuel injector perform a plurality of injections of gaseous fuel; determining a set of Fourier transforms in response to the measuring; determining an average injection quantity for the plurality of gaseous fuel injectors in response to a first subset of the Fourier transforms; determining a plurality of disaggregated injection quantities for a plurality of subsets of the plurality of gaseous fuel injectors in response to a second subset of the Fourier transforms; and operating the gaseous fueling system using the disaggregated injection quantities.

2. The process of claim 1, wherein the first subset of the Fourier transforms comprise one or more Fourier transforms taken at respective positive integer multiples of a fundamental frequency of operation of the plurality of gaseous fuel injectors.

3. The process of claim 2, wherein the first subset of the Fourier transforms comprise a first Fourier transforms taken a first positive integer multiple of the fundamental frequency and a second Fourier transforms taken a second positive integer multiple of the fundamental frequency.

4. The process of claim 1, wherein the second subset of the Fourier transforms comprises a set of sub-harmonics of a fundamental frequency of operation of the plurality of gaseous fuel injectors.

5. The process of claim 4, wherein the set of sub-harmonics comprises sub-harmonics for each fraction of a total number of injector firing events for the over the fundamental frequency. Page 32 of 40 130508684v1Attorney Docket No. CMI002-00114 6. The process of claim 1, wherein the gaseous fueling system is configured as a single point injection (SPI) system wherein the plurality of gaseous fuel injectors are configured to inject gaseous fuel at respective locations effective to supply fuel to any of the plurality of combustion cylinders.

7. The process of claim 6, wherein a total number of the plurality of gaseous fuel injectors is one of less than and greater than a total number of the plurality of combustion cylinders and a fundamental frequency of operation of the plurality of gaseous fuel injectors is lower than a fundamental frequency of operation of the combustion cylinders.

8. The process of claim 1, wherein the gaseous fueling system is configured as a multiple port injection (MPI) system, wherein a plurality of subsets of the plurality of gaseous fuel injectors are configured to inject gaseous fuel at respective locations effective to supply fuel individually to respective ones of the plurality of combustion cylinders.

9. The process of claim 8, wherein the plurality of subsets each comprise multiple injectors.

10. The process of claim 8, wherein and a fundamental frequency of operation of the plurality of gaseous fuel injectors is equal to a fundamental frequency of operation of the combustion cylinders.

11. The process of claim 1, wherein the operating the gaseous fueling system using the disaggregated injection quantities comprises modifying injector control logic using the disaggregated injection quantities and controlling the gaseous fuel injector using the modified injector control logic.

12. The process of claim 1, wherein the operating the gaseous fueling system using the disaggregated injection quantities comprises performing a diagnostic of the gaseous fuel injector using the disaggregated injection quantities. Page 33 of 40 130508684v1Attorney Docket No. CMI002-00114 13. A system comprising: an electronic control system in operative communication with a gaseous fueling system including a plurality of gaseous fuel injectors in fluid communication with a plurality of combustion cylinders the electronic control system being configured to: operate the plurality of gaseous fuel injector perform injections of gaseous fuel; measure pressure of gaseous fuel supplied to the plurality of gaseous fuel injectors during operation of the plurality of gaseous fuel injector perform a plurality of injections of gaseous fuel; determine a set of Fourier transforms in response to the pressure measurement; determine an average injection quantity for the plurality of gaseous fuel injectors in response to a first subset of the Fourier transforms; determine a plurality of disaggregated injection quantities for a plurality of subsets of the plurality of gaseous fuel injectors in response to a second subset of the Fourier transforms; and operate the gaseous fueling system using the disaggregated injection quantities.

14. The system of claim 13, wherein the first subset of the Fourier transforms comprise one or more Fourier transforms taken at respective positive integer multiples of a fundamental frequency of operation of the plurality of gaseous fuel injectors.

15. The system of claim 14, wherein the first subset of the Fourier transforms comprise a first Fourier transforms taken a first positive integer multiple of the fundamental frequency and a second Fourier transforms taken a second positive integer multiple of the fundamental frequency.

16. The system of claim 13, wherein the second subset of the Fourier transforms comprises a set of sub-harmonics of a fundamental frequency of operation of the plurality of gaseous fuel injectors. Page 34 of 40 130508684v1Attorney Docket No. CMI002-00114 17. The system of claim 16, wherein the set of sub-harmonics comprises sub-harmonics for each fraction of a total number of injector firing events for the over the fundamental frequency.

18. The system of claim 13, wherein the gaseous fueling system is configured as a single point injection (SPI) system wherein the plurality of gaseous fuel injectors are configured to inject gaseous fuel at respective locations effective to supply fuel to any of the plurality of combustion cylinders.

19. The system of claim 18, wherein a total number of the plurality of gaseous fuel injectors is less than a total number of the plurality of combustion cylinders and a fundamental frequency of operation of the plurality of gaseous fuel injectors is lower than a fundamental frequency of operation of the combustion cylinders.

20. The system of claim 13, wherein the gaseous fueling system is configured as a multiple port injection (MPI) system, wherein a plurality of subsets of the plurality of gaseous fuel injectors are configured to inject gaseous fuel at respective locations effective to supply fuel individually to respective ones of the plurality of combustion cylinders.

21. The system of claim 20, wherein the plurality of subsets each comprise multiple injectors.

22. The system of claim 20, wherein and a fundamental frequency of operation of the plurality of gaseous fuel injectors is equal to a fundamental frequency of operation of the combustion cylinders.

23. The system of claim 13, wherein the electronic control system is configured to operate Page 35 of 40 130508684v1Attorney Docket No. CMI002-00114 the gaseous fueling system using the disaggregated injection quantities comprises modifying injector control logic using the disaggregated injection quantities and controlling the gaseous fuel injector using the modified injector control logic.

24. The system of claim 13, wherein the electronic control system is configured to operate the gaseous fueling system using the disaggregated injection quantities comprises performing a diagnostic of the gaseous fuel injector using the disaggregated injection quantities.

25. A process of operating a gaseous fueling system including a plurality of gaseous fuel injectors in fluid communication with a plurality of combustion cylinders, the process comprising: operating the plurality of gaseous fuel injectors to perform injections of gaseous fuel; measuring pressure of gaseous fuel supplied to the plurality of gaseous fuel injectors during the operating the plurality of gaseous fuel injector perform a plurality of injections of gaseous fuel; determining a set of Fourier transforms for a plurality of sub-harmonic frequencies in response to the measuring; determining a sum of sinusoidal waveforms in response to the set of Fourier transforms; determining relative injected quantity differences between the plurality of gaseous fuel injectors in response to the sum of sinusoidal waveforms; and operating the gaseous fueling system in response to the relative injected quantity differences.

26. The process of claim 25, wherein the determining the set of Fourier transforms comprises determining an average gaseous fuel pressure of the operating and determining the set of Fourier transforms in response to the average gaseous fuel pressure.

27. The process of claim 25, wherein the sum of sinusoidal waveforms is determined in response to amplitudes and phases of the plurality of sub-harmonic frequencies. Page 36 of 40 130508684v1Attorney Docket No. CMI002-00114 28. The process of claim 25, wherein the determining relative injected quantity differences between the injectors is further in response to a relationship between injection event positions for the plurality of gaseous fuel injectors and corresponding local values of the sum of sinusoidal waveforms.

29. The process of claim 25, comprising: calculating an expected sum of the sinusoidal waveforms accounting for non-symmetry of flow passage geometry and pressure sensor location of the gaseous fueling system; determining a difference of the sum of sinusoidal waveforms and the expected sum of sinusoidal waveforms; and determining relative injected quantity in response to the difference and a relationship between injection event position for an injector and a relationship between injection event positions for the plurality of gaseous fuel injectors and corresponding local values of the sum of sinusoidal waveforms.

30. The process of claim 25, wherein the operating the gaseous fueling system in response to the relative injected quantity differences comprises balancing injection quantities among the plurality of gaseous fuel injectors by adjusting commanded on-times for one or more of the plurality of gaseous fuel injectors.

31. A system comprising: an electronic control system in operative communication with a gaseous fueling system including a plurality of gaseous fuel injectors in fluid communication with a plurality of combustion cylinders the electronic control system being configured to: operate the plurality of gaseous fuel injectors to perform injections of gaseous fuel; measure pressure of gaseous fuel supplied to the plurality of gaseous fuel injectors during the operating the plurality of gaseous fuel injector perform a plurality of injections of gaseous fuel; determine a set of Fourier transforms for a plurality of sub-harmonic frequencies in response to the pressure measurement; Page 37 of 40 130508684v1Attorney Docket No. CMI002-00114 determine a sum of sinusoidal waveforms in response to the set of Fourier transforms; determine relative injected quantity differences between the plurality of gaseous fuel injectors in response to the sum of sinusoidal waveforms; and operate the gaseous fueling system in response to the relative injected quantity differences.

32. The system of claim 31, wherein the electronic control system being configured to determine the set of Fourier transforms comprises the electronic control system being configured to determine an average gaseous fuel pressure of the operating and determine the set of Fourier transforms in response to the average gaseous fuel pressure.

33. The system of claim 31, wherein the sum of sinusoidal waveforms is determined in response to amplitudes and phases of the plurality of sub-harmonic frequencies.

34. The system of claim 31, wherein the electronic control system is configured to determine relative injected quantity differences between the injectors further in response to a relationship between injection event positions for the plurality of gaseous fuel injectors and corresponding local values of the sum of sinusoidal waveforms.

35. The system of claim 31, wherein the electronic control system is configured to: calculate an expected sum of the sinusoidal waveforms accounting for non-symmetry of flow passage geometry and pressure sensor location of the gaseous fueling system; determine a difference of the sum of sinusoidal waveforms and the expected sum of sinusoidal waveforms; and determine relative injected quantity in response to the difference and a relationship between injection event position for an injector and a relationship between injection event positions for the plurality of gaseous fuel injectors and corresponding local values of the sum of sinusoidal waveforms.

36. The system of claim 31, wherein the electronic control system being configured to operate the gaseous fueling system comprises the electronic control system being configured to Page 38 of 40 130508684v1Attorney Docket No. CMI002-00114 balance injection quantities among the plurality of gaseous fuel injectors by adjusting commanded on-times for one or more of the plurality of gaseous fuel injectors. Page 39 of 40 130508684v1

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