Patent Grant
9638116
The present disclosure relates to a system and method for controlling an internal combustion engine. In particular, the present disclosure relates to a system and method for controlling an internal combustion engine via closed-loop control.
Internal combustion engines convert chemical energy associated with a mixture of air and fuel into mechanical power by combustion of the mixture of air and fuel. In particular, many internal combustion engines burn carbon-based fuels, such as, for example, gasoline, diesel fuel, alcohol such as methane and ethane, and/or combinations thereof, such as, for example, a gasoline-alcohol combination sometimes referred to as “E85” (i.e., a mixture of about 85% ethanol and about 15% gasoline). The combustion of carbon-based fuels converts the chemical energy associated with the carbon-based fuel into mechanical power by releasing heat generated during combustion, which, in turn, creates pressure that drives a mechanism, such as, for example, the piston of a reciprocating engine or the rotor of a rotary engine.
Along with releasing heat, combustion of the mixture of air and fuel results in the emission of by-products of the combustion process. For example, combustion may result in the emission of unburned fuel, hydrocarbons such as methane (CH4), oxides of carbon (COx) such as carbon monoxide (CO) and carbon dioxide (CO2), oxides of nitrogen (NOX), water vapor, ozone (O3), and/or other compounds. Of particular concern is the emission of “greenhouse gases,” such as, for example, carbon dioxide (CO2), methane (CH4), ozone (O3), and water vapor.
Renewed interest in the conservation of natural resources and the environment has led to an increased desire to improve the fuel efficiency and reduce the emissions of internal combustion engines. One way to increase the efficiency of internal combustion engines is to harness the maximum amount of energy associated with a unit volume of fuel during combustion by controlling the combustion process such that a greater proportion of the fuel is burned during combustion. This greater efficiency, in turn, effectively reduces the amount of exhaust emissions created during combustion by virtue of the combustion of less fuel. Further, as a greater proportion of the fuel used during operation of the internal combustion engine is completely burned, the amount of pollutants associated with the emissions fuel may be reduced.
Although a number of prior attempts have been made to obtain a more complete combustion of fuel, those attempts have suffered from a number of possible drawbacks. For example, some prior attempts have required relatively expensive control systems, rendering such systems economically unattractive for certain applications. Other attempts have been found less reliable, rendering them unsuitable for long-term use and/or some applications.
Yet another possible drawback with some prior systems relates to an inability of the systems to tailor operation of the internal combustion engine to particular operating circumstances. For example, it may be desirable under some operating circumstances for an internal combustion engine to achieve maximum efficiency at the expense of responsiveness to changes in load. Such operational circumstances may occur, for example, when the internal combustion engine is being used at a relatively steady engine speed and/or a relatively constant load, such as, for example, the operational circumstances experienced by a lawn mower, or the operational circumstances experienced by a car, boat, or airplane when cruising at a relatively constant speed and/or altitude. On the other hand, some operating circumstances may result in a desire for increased responsiveness to changes in load at the expense of maximum efficiency. Such operational circumstances may occur, for example, when the internal combustion engine is being used in a car being driven in a city's stop-and-go traffic, or in an airplane during take-off or landing operations. Thus, it may be desirable to control the operation of an internal combustion engine in an efficient manner that permits the operation to be changed based on the operating circumstances, while minimizing undesirable exhaust emissions.
In the following description, certain aspects and embodiments will become evident. It should be understood that the invention, in its broadest sense, could be practiced without having one or more features of these aspects and embodiments. It should be understood that these aspects and embodiments are merely exemplary.
One aspect of the present disclosure relates to a system for controlling operation of an internal combustion engine. The system includes a controller configured to send signals for controlling at least one of air-fuel ratio, spark-ignition timing, and fuel injection timing to an internal combustion engine. The system further includes a sensor configured to send a signal indicative of exhaust gas temperature to the controller. The system is configured to control at least one of air-fuel ratio, spark-ignition timing, and fuel injection timing based on a signal indicative of at least one of an operating condition of the internal combustion engine and load on the internal combustion engine, and a difference between a target exhaust gas temperature and the signal indicative of the exhaust gas temperature.
According to another aspect, a machine includes an internal combustion engine and a system for controlling operation of the internal combustion engine. The system includes a controller configured to send signals configured to control at least one of air-fuel ratio, ignition timing, and fuel injection timing to the internal combustion engine. The system further includes a sensor configured to send a signal indicative of exhaust gas temperature to the controller. The controller is configured to control at least one of air-fuel ratio, ignition timing, and fuel injection timing based on a signal indicative of at least one of an operating condition of the internal combustion engine and load on the internal combustion engine, and a difference between a target exhaust gas temperature and the signal indicative of the exhaust gas temperature.
According to yet another aspect, a method for controlling operation of an internal combustion engine includes receiving a signal indicative of at least one of an operating condition of the internal combustion engine and load on the internal combustion engine, receiving a signal indicative of exhaust gas temperature of the internal combustion engine, and controlling at least one of air-fuel ratio, spark-ignition timing, and fuel injection timing based on the signal indicative of at least one of an operating condition and load, and a difference between the signal indicative of exhaust gas temperature and a target exhaust gas temperature.
According to still a further aspect, a method of providing data for controlling operation of an internal combustion engine includes operating an internal combustion engine and adjusting at least one of air-fuel ratio, spark-ignition timing, and fuel injection timing. The method further includes measuring a signal indicative of exhaust gas temperature, creating correlations between at least one of the air-fuel ratio, spark-ignition timing, and fuel injection timing and the exhaust gas temperature, and storing the correlations in a data storage device.
According to yet another aspect, a system for controlling operation of an internal combustion engine includes a controller configured to send signals for controlling air-fuel ratio to an internal combustion engine, and a sensor configured to send a signal indicative of exhaust gas temperature of the engine to the controller. The controller is configured to send a signal indicative of a commanded air-fuel ratio to the engine based on correlations between an operating condition of the engine, air-fuel ratio, and exhaust gas temperature stored in memory. The controller is further configured to send signals indicative of a plurality of different air-fuel ratios to the engine, such that the engine operates at each of the plurality of different air-fuel ratios. The controller is also configured to receive a plurality of signals indicative of exhaust gas temperature associated with operation of the engine at each of the plurality of different air-fuel ratios. The controller is configured to estimate a peak exhaust gas temperature associated with the operating condition based on the plurality of signals indicative of exhaust gas temperature.
According to still a further aspect, a system for controlling operation of an internal combustion engine includes a controller configured to send signals for controlling air-fuel ratio to an internal combustion engine, and a sensor configured to send a signal indicative of exhaust gas temperature of the engine to the controller. The controller is configured to send a signal indicative of a commanded air-fuel ratio to the engine based on correlations between an operating condition of the engine, air-fuel ratio, and exhaust gas temperature stored in memory. The controller is also configured to send signals indicative of a plurality of different air-fuel ratios to the engine, such that the engine operates at each of the plurality of different air-fuel ratios. The controller is further configured to receive a plurality of signals indicative of exhaust gas temperature associated with operation of the engine at each of the plurality of different air-fuel ratios. The controller is also configured to determine whether there is a fault associated with operation of one of the sensor and a fuel injector of the engine.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate several embodiments of the invention and together with the description, serve to explain the principles of the invention. In the drawings,
Reference will now be made in detail to exemplary embodiments of the invention. Wherever possible, the same reference numbers are used in the drawings and the description to refer to the same or like parts.
According to some embodiments, the system 12 may be configured to control operation of any type of internal combustion engine 14, including, but not limited to, reciprocating piston-driven engines, rotary engines, gas turbine engines, spark-ignition engines, and/or compression-ignition engines, such as diesel engines. For example, some embodiments of the system 12 may be configured to control the air-to-fuel mixture ratio (“the air-fuel ratio” or AFR), the spark-ignition timing, and/or the fuel injection timing (e.g., for a compression-ignition engine).
According to the exemplary embodiment depicted in
According to some embodiments, internal combustion engine 14 includes an intake system 26 configured to receive air and fuel 22 and mix the air and fuel 22 being supplied to the internal combustion engine 14 for combustion. For example, the intake system 26 may include a carburetor and/or one or more fuel injectors for supplying fuel to a combustion chamber (e.g., of a cylinder) of the internal combustion engine 14. According to some embodiments that include one or more carburetors, the carburetor(s) may operate to provide a supply of fuel and a supply of air to an intake manifold in flow communication with one or more combustion chambers of the internal combustion engine 14. According to some embodiments that include one or more fuel injectors, the fuel injector(s) may inject fuel into an intake manifold and/or directly into one or more combustion chambers, where the fuel may mix with air and ignite.
The exemplary embodiment schematically-depicted in
According to the embodiment depicted in
The controller 30 may include one or more processors, microprocessors, central processing units, on-board computers, electronic control modules, and/or any other computing and control devices known to those skilled in the art. The controller 30 may be configured run one or more software programs or applications stored in a memory location, read from a computer-readable medium, and/or accessed from an external device operatively coupled to the controller 30 by any suitable communications network.
The exemplary embodiment depicted in
As schematically-depicted in
The exemplary embodiment depicted in
Referring to the exemplary embodiment depicted in the block diagram of
For example, referring to
As depicted in
If the operating conditions are reduced (e.g., the engine speed and/or air-mass-per charge is reduced) relative to the operating conditions represented by curve A, the relationship between the air-fuel ratio and the exhaust gas temperature may be represented by curve B, which indicates a general reduction in exhaust gas temperature for a given air-fuel ratio. If, on the other hand, the operating conditions are increased relative to the operating conditions depicted in curve A, the relationship between the air-fuel ratio and the exhaust gas temperature may be represented by curve C, which indicates a general increase in exhaust gas temperature for a given air-fuel ratio.
According to some embodiments, the air-fuel ratio depicted in
In a similar manner, for a compression-ignition engine, timing of the fuel injection into the combustion chamber may also impact the exhaust gas temperature. For example, when the fuel is injected into the combustion chamber earlier than the time at which the most complete combustion would occur (i.e., the optimum, stoichiometric injection timing), the exhaust gas temperature may be relatively low. As the injection timing is progressively delayed up until the optimum injection timing, the exhaust gas temperature may increase until reaching a peak at the point of optimum injection timing. Conversely, as the injection timing is delayed past the optimum injection timing, the exhaust gas temperature may be reduced.
According to some embodiments, the controller 30 may be configured to control the operation of the internal combustion engine 14 in a manner related to the relationship between the exhaust gas temperature and at least one of the air-fuel ratio, ignition timing, and fuel injection timing. For example, the storage device 46 may include tables and/or maps of the correlations between exhaust gas temperature and at least one of air-fuel ratio, ignition timing, and fuel injection timing in relation to different operating conditions of the internal combustion engine 14. According to some embodiments, rather than (or in addition to) the maps and/or tables, the storage device 46 may include equations representing the relationships between the exhaust gas temperature and at least one of the air-fuel ratio, ignition timing, and fuel injection timing in relation to different operating conditions of the internal combustion engine 14.
According to some embodiments, the controller 30 may be configured to control at least one of the air-fuel ratio, ignition timing, and fuel injection timing, such that the internal combustion engine 14 operates in relation to curves, for example, as shown in
According to some embodiments, the controller 30 may be configured to control at least one of the air-fuel ratio, ignition timing, and fuel injection timing, such that internal combustion engine 14 performs with certain desired characteristics based on, for example, certain operational situations. For example, under some circumstances, it may be desirable for the internal combustion engine 14 to be relatively more responsive to changes in the operating condition or load 18 at the expense of, for example, efficiency. According to some embodiments of internal combustion engine 14, the internal combustion engine 14 may tend to be more responsive to changes in operating condition or load when operating with an air-fuel ratio relatively more rich than the theoretical, stoichiometric mixture ratio AFRs. Thus, in operational situations where it may be desirable to operate the internal combustion engine such that is relatively more responsive to changes in operating condition or load, it may be desirable to select a mixture ratio slightly rich of the theoretical, stoichiometric mixture ratio AFRs. Conversely, under some operational situations, it may be desirable for the internal combustion engine 14 to be relatively more efficient at the expense of, for example, responsiveness to changes in operating condition or load. According to some embodiments of internal combustion engine 14, the internal combustion engine may tend to be more efficient when operating with a mixture ratio relatively more lean than the theoretical, stoichiometric mixture ratio AFRs. Thus, in operational situations where it may be desirable to operate more efficiently, it may be desirable to select a mixture ratio slightly lean of the theoretical, stoichiometric mixture ratio AFRs.
According to some embodiments, the controller 30 may be configured to control operation of the internal combustion engine 14 to achieve desirable operational characteristics in relation to certain operational situations. For example, if it is desirable to operate the internal combustion engine 14 in a manner that results in improved responsiveness to changes in operation conditions or load, the controller 30 may be configured to control at least one of the air-fuel ratio, ignition timing, and fuel injection timing, such that the internal combustion engine 14 operates slightly rich of the theoretical, stoichiometric mixture ratio AFRs. If it is desirable to operate the internal combustion engine 14 in a manner that results improved efficiency, the controller 30 may be configured to control at least one of the air-fuel ratio, ignition timing, and fuel injection timing, such that the internal combustion engine 14 operates slightly lean of the theoretical, stoichiometric mixture ratio AFRs.
According to some embodiments, the controller 30 may be configured to control the relative richness and/or leanness of the combustion by receiving a signal indicative of the exhaust gas temperature Texhaust via one or more sensor(s) 36 and communication link 38, and controlling at least one of the air-fuel ratio, ignition timing, and fuel injection timing, such that the exhaust gas temperature that correlates to the desired air-fuel ratio for a given operation condition or load is substantially achieved. Referring to
Once the target exhaust gas temperature Ttarget has been provided, the controller 30 may be configured to send a control signal to an electronic control unit (ECU) 48, which, in turn, may send a control signal C via communication link 44 to the control module 42, which may be configured to control at least one of the air-fuel ratio, ignition timing, and fuel injection timing of the internal combustion engine 14 to achieve the target exhaust gas temperature Ttarget. According to some embodiments, the ECU 48 may be, for example, a single lever power controller. For example, the single lever power controller may be similar to single lever power controllers disclosed in commonly-assigned U.S. Pat. Nos. 6,171,055, 6,340,289, and 7,011,498, the subject matter of which is incorporated herein by reference. The use of other types of ECUs is contemplated. The one or more sensor(s) 36 provide(s) a signal indicative of the actual exhaust gas temperature Texhaust, which is sent to controller 30 via communication link 38. The controller 30 compares via, for example, a comparator 50, the actual exhaust gas temperature Texhaust to the target exhaust gas temperature Ttarget. If a difference ΔT of more than a predetermined deadband (i.e., within a certain range of the target exhaust gas temperature Ttarget) around the target exhaust gas temperature Ttarget exists, the difference ΔT is communicated to the ECU 48, which sends a signal to the control module 42 in order to adjust at least one of the air-fuel ratio, ignition timing, and fuel injection timing in order to more closely achieve the target exhaust gas temperature Ttarget.
Following the adjustment, the one or more sensor(s) 36 send a signal indicative of the actual exhaust gas temperature Texhaust to, for example, the comparator 50 of the controller 30. According to some embodiments, the comparator 50 may be configured to determine whether the actual exhaust gas temperature Texhaust is within the deadband of the target exhaust gas temperature Ttarget. If the exhaust gas temperature Texhaust is not within the deadband, the controller 30 determines whether the last adjustment made by the control module 42 resulted in the current actual exhaust gas temperature Texhaust2 being closer to the target exhaust gas temperature Ttarget than the previously measured actual exhaust gas temperature Texhaust1. If the current actual exhaust gas temperature Texhaust2 is closer to the target exhaust gas temperature Ttarget, then the ECU 48 sends a signal to the control module 42 to adjust at least one of the air-fuel ratio, ignition timing, and fuel injection timing in the same direction as the previous adjustment. If, on the other hand, the current actual exhaust gas temperature Texhaust2 is farther from the target exhaust gas temperature Ttarget than the previously measured exhaust gas temperature Texhaust1, the ECU 48 sends a signal to the control module 42 to adjust at least one of the air-fuel ratio, ignition timing, and fuel injection timing in the opposite direction. This comparison between the current actual exhaust gas temperature Texhaust2 and the previously measured exhaust gas temperature Texhaust1 may be desirable, since each measured exhaust gas temperature may correspond to two distinct air-fuel ratio settings, ignition timing settings, and/or fuel injection timing settings. As a result, based on which side of stoichiometric combustion (e.g., at AFRs) the exhaust gas temperature curve the settings lie, the adjustment of the air-fuel ratio, ignition timing, and/or fuel injection timing may result in a change in the actual exhaust gas temperature Texhaust in a direction opposite (i.e., higher instead of lower, or lower instead of higher) the desired direction. The controller 30 continues this closed-loop exhaust gas temperature comparison process until the actual exhaust gas temperature Texhaust is within the deadband of the target exhaust gas temperature Ttarget. Once within the deadband, the controller 30 continues to the comparison process to substantially maintain the actual exhaust gas temperature Texhaust within the deadband of the target exhaust gas temperature Ttarget.
According to some embodiments, as one or more of the ambient conditions, operating conditions, and signal indicative of load 18 changes, the controller 30 changes the target exhaust gas temperature Ttarget in relation to the look-up tables, maps, and/or equations in the storage device 46. For example, as the ambient temperature associated with the air entering the intake system 26 increases, the target exhaust gas temperature Ttarget provided by the controller 30 may tend to increase. Conversely, as the ambient temperature decreases, the target exhaust gas temperature Ttarget provided by the controller 30 may tend to decrease. Further, as the operating conditions of the engine 14 increase (e.g., the engine speed and/or air-mass-per-charge increases), the target exhaust gas temperature Ttarget provided by the controller 30 may tend to increase, whereas when the operating conditions decrease, the target exhaust gas temperature Ttarget provided by the controller 30 may tend to decrease. According to some embodiments, as the load on the internal combustion engine 14 increases, the target exhaust gas temperature Ttarget provided by the controller 30 may tend to increase, whereas when the load on the internal combustion engine 14 decreases, the target exhaust gas temperature Ttarget provided by the controller 30 may tend to decrease.
According to some embodiments, the signal indicative of load L may change due, at least in part, to a number factors. For example, as schematically-depicted in
According to some embodiments, other factors may be contribute to the signal indicative of load L. The machine 10 may, for example, include a manual adjustment configured to alter the operating characteristics of the internal combustion engine 14. For example, the manual adjustment may provide an operator of the machine 10 with the ability to alter the operation of the internal combustion engine 14 to operate more responsively to changes in load and/or operate more efficiently. The manual adjustment may permit, for example, selection of a “power” mode and/or an “efficiency” mode. In the “power” mode, for example, the controller 30 may be configured to set the target exhaust gas temperature Ttarget, such that the resulting air-fuel ratio is at least slightly richer than the theoretical, stoichiometric mixture ratio AFRs. An operator might be inclined to select the exemplary “power” setting when the machine 10 is, for example, an air vehicle that is about to take-off or land. Selecting the exemplary “power” mode setting might result in a higher power output and/or increased responsiveness of the internal combustion engine 14. In the “efficiency” mode, for example, the controller 30 may be configured to set the target exhaust gas temperature Ttarget, such that the resulting air-fuel ratio is at least slightly leaner than the theoretical, stoichiometric mixture ratio AFRs. An operator might be inclined to select the exemplary “efficiency” mode when the machine 10 is, for example, an air vehicle that has reached cruising altitude and is flying at a relatively steady cruising speed and/or a relatively steady altitude. Selecting the exemplary “efficiency” mode setting may result in improved fuel efficiency.
According to some embodiments, a signal indicative of the exemplary mode settings may contribute to the signal indicative of the load L, such that the controller 30 sets the target exhaust gas temperature Ttarget accordingly. Once the target exhaust gas temperature Ttarget has been set, it may be desirable for the controller 30 to adjust at least one of the air-fuel ratio, ignition timing, and fuel injection timing such the internal combustion engine 14 operates on the side of the theoretical, stoichiometric mixture ratio AFRs (i.e., relatively rich or relatively lean of stoichiometric), since the actual exhaust gas temperature Texhaust coincides with two mixture ratios for each given load, one mixture ratio rich of the theoretical, stoichiometric mixture ratio AFRs and one mixture ratio lean of the theoretical, stoichiometric mixture ratio AFRs (see
According to some embodiments, the controller 30 may be configured to determine whether to operate the internal combustion engine 14 rich of stoichiometric combustion, substantially at stoichiometric combustion, or lean of stoichiometric combustion based on operating parameters related to the machine 10. For example, if the throttle position is greater than a certain percentage of full throttle (e.g., greater than about 80% of full throttle), the controller 30 may be configured to provide a target exhaust gas temperature Ttarget that is at least slightly rich of stoichiometric combustion for the given load 18, which may increase the responsiveness and/or power of the internal combustion engine 14. If, on the other hand, the throttle position is less than a certain percentage of full throttle (e.g., less than about 35% of full throttle), the controller 30 may be configured to provide a target exhaust gas temperature Ttarget that is at least slightly lean of stoichiometric combustion for the given load 18, which may increase the efficiency of the internal combustion engine 14. If the throttle position is within a certain intermediate range of full throttle (e.g., more than about 35% but less than about 80% of full throttle), the controller 30 may be configured to provide a target exhaust gas temperature Ttarget that provides substantially stoichiometric combustion for the given load 18. Similarly, according to some embodiments, if the engine speed is greater than a certain engine speed, the controller 30 may be configured to provide a target exhaust gas temperature Ttarget that is at least slightly rich of stoichiometric combustion for the given load 18. If, on the other hand, the engine speed is less than a certain engine speed, the controller 30 may be configured to provide a target exhaust gas temperature Ttarget that is at least slightly lean of stoichiometric combustion for the given load 18. If the engine speed falls within a certain intermediate range of possible engine speeds, the controller 30 may be configured to provide a target exhaust gas temperature Ttarget that provides substantially stoichiometric combustion for the given load 18. According to some embodiments, the ECU 48 may be configured to provide signals indicative of at least one of the throttle position and engine speed to the controller 30.
Some embodiments of the controller 30 may be configured to factor fluctuations in the signal indicative of the load L (or a relative lack of fluctuations) into a determination of the target exhaust gas temperature Ttarget. For example, the controller 30 may be configured to set a target exhaust gas temperature Ttarget that results in operation of the internal combustion engine 14 at least slightly rich of stoichiometric if, for example, the signal indicative of load L fluctuates more than a certain amount, which may result in a desire for the internal combustion engine 14 to operate in a manner that is relatively more responsive to changes in the load 18 on the internal combustion engine 14. Conversely, the controller 30 may be configured to set a target exhaust gas temperature Ttarget that results in operation of the internal combustion engine 14 at least slightly lean of stoichiometric if, for example, the signal indicative of load L remains below a certain threshold amount of fluctuation, which may result in a desire for the internal combustion engine 14 to operate in a manner that is relatively more efficient.
The look-up tables and/or maps of the correlations between exhaust gas temperature and at least one of air-fuel ratio, ignition timing, and fuel injection timing, may be generated via a combination of theoretical calculation and empirically-derived data. For example, thermodynamic theory may be used to determine projected exhaust gas temperatures for stoichiometric combustion based on ambient air conditions, chemical energy associated with the air-fuel ratio, and an estimated amount of work produced by combustion of the air-fuel ratio, which may correlate to the operating condition of the engine and/or the magnitude of the load 18 on the engine. Such theoretical calculations may be based on, for example, enthalpy calculations. Further, such calculations may be performed for a number of different values for one or more of the ambient air conditions, chemical energy associated with the air-fuel ratio, and the estimated amount of work to determine exhaust gas temperatures associated with stoichiometric combustion for the changed value sets.
According to some embodiments, the exhaust gas temperatures calculated based on thermodynamic theory may be used as a reference point for empirically-deriving actual exhaust gas temperature data while operating an actual internal combustion engine on a test bed, such as, for example, a dynamometer, and recording the actual data points associated with its operation upon changing the ambient air conditions and the amount of actual work produced by the internal combustion engine 14. For example, the exhaust gas temperature can be recorded as at least one of the air-fuel ratio, ignition timing, fuel injection timing, operating condition (e.g., engine speed and/or air-mass-per-charge), and load 18 on the internal combustion engine 14 is/are changed. This process may be used to produce the look-up tables, maps, and or equations for storage in the storage device 46, which may be used by the controller 30. According to some embodiments, the empirical analysis may be performed with or without performing the theoretical thermodynamic analysis. Further, according to some embodiments, the data points, regardless of how they are determined, may be represented by mathematical equations, and the controller 30 may be configured to control operation of the internal combustion engine 14 by using the mathematical equations rather than (or in addition to) using the look-up tables and/or maps.
In the exemplary embodiment of system 12 shown in
However, due to, for example, engine wear, sensor degradation, and/or fuel differences, the feed-forward correlations in block 60 may not be as accurate as desired. Thus, the commanded air-fuel ratio provided at block 60 may not be as accurate as desired, possibly resulting in a loss of efficiency and/or power during operation of the engine 14.
The exemplary controller shown in
For example, as shown in
According to some embodiments, during the estimation routine, the commanded air-fuel ratio is swept (e.g., adjusted through a range of air-fuel ratio settings) to compare to correlate the air-fuel ratios with actual exhaust gas temperatures determined by the exhaust gas temperature sensor. The data points generated from the estimation routine can be used to generate an air-fuel ratio vs. exhaust gas temperature curve, as explained in more detail with respect to
Exemplary operation of the estimation routine is explained below in the context of general aviation. In an airplane, a pilot may manually set the air-fuel ratio by first determining the peak of the exhaust gas temperature profile during steady-state flight conditions. Once the peak EGT is determined, the AFR may be adjusted up or down to set for lean operation of the engine 14, for example, based on a known offset from the peak EGT that may be provided by, for example, the engine manufacturer.
The exemplary system 12 may operate to automate the pilot's actions. For example, the system 12 may include a steady-state detection function that identifies steady-state flight conditions and initiates the estimation routine, which adjusts the air-fuel ratio through a range of different air-fuel ratios, so that the estimation routine can determine the peak exhaust gas temperature and the air-fuel ratio (“the peak air-fuel ratio”) that corresponds to the peak exhaust gas temperature. The estimation routine determines where the peak EGT and peak air-fuel ratio occurs and stores them in two-dimensional look-up tables (e.g., in the EGT correction tables). According to some embodiments, the estimation routine is repeated for one or more cylinders (e.g., for each cylinder) of the engine 14 in a coordinated, sequential manner.
For example, during operation, the system 12 may first determine whether steady-state conditions exist. When steady-state conditions are detected, the estimation routine is performed on a first cylinder of engine 14. Once the estimation routine has been completed for the first cylinder, the estimation routine is preformed on a second cylinder of engine 14, and this sequence is repeated for a number of cylinders of the engine 14 (e.g., all of the cylinders of engine 14).
Once the estimation routine has been performed on the cylinders, the results of the estimation routine may be clipped based on the mean and variance of the results for the cylinders to ensure that consistent corrections across all of the cylinders, and all of the EGT correction tables may be updated to reflect a change in air-fuel ratio between the initially commanded air-fuel ratio from the feed-forward tables.
While still at the same operating condition of engine 14, the estimation routine may be performed again, beginning with a cylinder other than the first cylinder on which the estimation routine was initially performed. At this performance of the estimation routine, the target air-fuel ratio is adjusted by the change in air-fuel ratio determined and stored during the performance of the previous estimation routine. This results in a new commanded air-fuel ratio, and the sequence described above may be repeated for all the cylinders subjected to the estimation routine.
According to some embodiments, the performance of estimation routine is suspended if the system determines that the engine 14 is no longer operating at steady-state conditions. If the estimation routine is suspended, the system continues to store the correction factors in the EGT correction tables, and the corrected air-fuel ratio commands are used during operation of the engine 14 whenever the estimation routine is inactive. According to some embodiments, the estimation routine is performed with a slow slew rate on the feed-forward correction to prevent a step change in the air-fuel ratio command when the estimation routine is suspended.
According to some embodiments, the system 12 is configured to determine whether the engine 14 is operating at steady-state based on one or more of throttle position, air-mass-per-charge, exhaust gas temperature, and engine speed. Because exhaust gas temperature is expected to change during the estimation routine and feedback control, settled exhaust gas temperature may be used as a condition to enter steady-state, but not to leave it. According to some embodiments, steady-state is determined only at operating conditions where the air-fuel ratio to exhaust gas temperature responsiveness is sufficient for the estimation routine to work. Such conditions may be stored in a tables, and once steady state conditions are detected, they may be maintained for 15 seconds before steady-steady is conformed for commencement of the estimation routine.
According to some embodiments, a pilot may disable the estimation routine by changing the throttle position, which will change the operating condition. Following suspension of steady-state, a predetermined time lapse (e.g., 10 seconds) may be required prior to a determination of a new steady-state condition.
During a cylinder test of the estimation routine, the air-fuel ratio for the tested cylinder is commanded using a series of steps (e.g., seven steps) at different air-fuel ratio levels. For each air-fuel ratio step, the commanded air-fuel ratio is held long enough for the associated exhaust gas temperature to settle for accurate measurement. The duration of each step may be based on the operating condition of the engine 14 and may vary. For example, the duration of the step may vary between about 12 and 18 seconds. The detected exhaust gas temperature at each step may be used to construct an air-fuel ratio vs. exhaust gas temperature curve for the estimation of the peak exhaust gas temperature and associated peak air-fuel ratio.
According to some embodiments, the estimation routine will begin with the air-fuel ratio target set equal to the commanded air-fuel ratio from the feed-forward tables. The next two steps will be in the rich direction (i.e., a smaller air-fuel ratio). If the exhaust gas temperature initially drops and thereafter increases, the first data point (i.e., the target air-fuel ratio) is dropped. This prevents the estimation routine from tracking to the lean exhaust gas peak that may typically occur between air-fuel ratio values of 1.2 and 1.3. Subsequent steps will locate the peak exhaust gas temperature by taking air-fuel ratio steps of, for example, increments of 0.1.
As the estimation routine increases the air-fuel ratio by increments, absolute air-fuel ratio limits of, for example, 0.75 minimum and 1.15 maximum are enforced along with relative air-fuel ratio limits about the previous peak estimate of the air-fuel ratio. If during the estimation routine, the commanded air-fuel ratio achieves either the minimum or maximum air-fuel ratio limits, or the estimation routine predicts that the search direction is away from the peak exhaust gas temperature, the search direction will be reversed. According to some embodiments, if the search direction is reversed, the step size is reduced to provide finer resolution in the commanded air-fuel ratio vs. exhaust gas temperature curve. This may tend to provide more data points near the peak, which permits improved estimation of the peak exhaust gas temperature and peak air-fuel ratio.
Once the sweep is completed for a given cylinder, a routine may be applied to determine the peak exhaust gas temperature and peak air-fuel ratio. According to some embodiments, a series of checks may be performed to verify the validity of the peak estimation. If the peak estimation is performed for more than one cylinder, the peak estimates may be checked for consistency. If an estimated peak for one cylinder is judged inconsistent with the peak estimate for the other cylinders, it may be clipped to be closer to the mean peak estimate of the other cylinders. Upon completion of the estimation routine, the change in peak estimate for the air-fuel ratio may be saved as a correction factor in the exhaust gas temperature correction table. Thereafter, the correction factor may be applied to the values of the feed-forward tables.
As shown in
According to the example shown in
According to some embodiments, the system 12 may be configured for fault detection. For example, exhaust gas temperature may be used to detect injector failure or sensor error. For example, based on exhaust gas temperature, one or more of the following failure modes may be detected: the EGT sensor has shorted to ground, the EGT sensor has shorted to power, the EGT sensor has shorted to wire harness, the EGT sensor has malfunctioned, the fuel injector remains open, the fuel injector remains closed, and the fuel injector provides incorrect fuel metering.
For example, EGT sensor faults/failures may be detected by monitoring the measured exhaust gas temperature. If the EGT sensor fails, the system may disable the estimation routine for the cylinder associated with the failed sensor. The EGT-based fault/failure detection for the fuel injector for the affected cylinder may also be disabled. According to some embodiments, if the sensor shorts to ground or the power supply, the EGT may immediately jump to a limit value. If the EGT falls outside minimum or maximum limits, the sensor may be identified as having failed.
According to some embodiments, the measurement function of an EGT sensor may be continuous. In such case, if the EGT change between cycles of the sensor exceeds a pre-determined limit, then the sensor may be identified as having failed.
In-range sensor failures may be detected by computing the difference of each EGT measurement from the mean of all other healthy EGT measurements. This value, or EGT offset, may be compared against several thresholds to detect sensor and/or injector failures. A cylinder may be deemed to have a healthy EGT measurement if its sensor has not failed, and that cylinder has not run any injector diagnostic tests within a predetermined time (e.g., within the past 30 seconds). According to some embodiments, one failed sensor may cause large EGT offsets for all cylinders of the engine. Thus, it may be desirable to evaluate only the healthy cylinder with the largest EGT offset. This restriction may serve to prevent one failure from triggering false alarms on other cylinders.
According to some embodiments, the EGT offset may be compared (i.e., substantially continuously) against two coarse thresholds, a maximum coarse EGT threshold and a minimum coarse EGT threshold. Exceeding the maximum coarse EGT threshold indicates a sensor failure, whereas exceeding the minimum coarse EGT threshold may indicate a sensor or injector failure.
According to some embodiments, while operating in steady state, changes to EGT offset may be compared against finer thresholds, a maximum finer threshold and a minimum finer threshold. The EGT offset of all cylinders is latched upon entering steady state, and thereafter these finer thresholds are active while no cylinder is performing the estimation routine. The latched values may also be invalidated if the failure status of any sensor or injector changes within the current steady state event. In such case, only the coarse EGT thresholds may be enforced.
According to some embodiments, each fuel injector may be supplied with fuel via two injector lanes. For such embodiments, during normal operation, the two injector lanes share control of the fuel metering, such that each of the two injector lanes inject about half of the fuel during a combustion cycle. However, the system 12 may be configured to alter this distribution of fuel in response to injector failures, or to facilitate identification of injector failures.
According to some embodiments, if no injector failures are detected, the system operates according to a default fuel distribution for the two injector lanes. If, however, an injector lane failure occurs, then the system 12 may alter the fuel distribution such that the non-failed injector lane supplies all of the fuel for the affected cylinder. According to some embodiments, even though only a single injector lane is operational, the estimation routine may still be performed based on whether the system detects steady-state operation of the engine 14. According to some embodiments, the system 12 may be configured to cut-off fuel supply to a cylinder when neither injector lane is operational.
As noted above, an EGT offset below the minimum coarse EGT threshold may indicate either a failed sensor or a failed injector. To identify the failed subsystem, the controller 30 may trigger an injector lane test. For example, if on any cylinder, the change in peak air-fuel ratio differs by more than a predetermined amount from the mean values of other cylinders, then an injector lane test may be preformed for that cylinder. As with the check on EGT offset, only the cylinder with the largest EGT offset may fail. This behavior is based on the assumption that only one cylinder will fail at a time, and that the one failed cylinder could induce false-positives when comparing the results of other cylinders to a mean value.
A low exhaust gas temperature measurement identifies either a sensor or fuel injector failure. According to some embodiments, the system 12 may be configured to identify the failed subsystem by commanding fuel from each injector lane independently, while monitoring exhaust gas temperature. If measured exhaust gas temperature is much higher when using a single injector, then the other injector is failed, while the high-EGT injector and EGT sensor are healthy. If, on the other hand, there is no exhaust gas temperature differential when switching between lanes, or the exhaust gas temperature is low for both injectors, then a failed EGT sensor may be the cause. A failed-open injector may also trigger this response, and therefore, be labeled as a sensor failure. As the system 12 may not have the ability to rectify a failed-open injector, this behavior is acceptable.
The mode of operation of the system 12 during an injector lane test may be dependent upon the triggering event. For example, if low-exhaust gas temperature is detected while the estimation routine is inactive, then the system 12 may operate each injector lane independently for a short time period. The EGT offset may be saved at the end of the time period, and thereafter the two offset values may be compared to determine which lane is operating properly. If exhaust gas temperature is significantly higher when using a single injector, then the other injector is identified as having failed. If there is a negligible exhaust gas temperature difference between injector lanes, then the sensor is identified as having failed.
If low exhaust gas temperature is detected during performance of the estimation routine, then each injector lane is commanded to sweep through the full range of air-fuel ratios. The minimum EGT offset for each injector lane may be determined, beginning a predetermined time into the sweep (e.g., several seconds into the sweep). These values for each injector lane may thereafter be compared to determine which injector lane is healthy. The controller 30 will identify the sensor as having failed if there is a negligible exhaust gas temperature difference between the two injector lanes.
According to some embodiments, an out-of-range change in air-fuel ratio peak result on any given cylinder may also trigger the diagnostic air-fuel ratio sweep. For example, if during an estimation routine the change in air-fuel ratio peak for a cylinder is significantly different than the change in air-fuel ratio peak for other cylinders, the diagnostic air-fuel ratio sweep may be performed. It may be assumed that if an injector has a large enough fuel-metering bias to trigger this test, then it will cause the cylinder to misfire at some point within the sweep. Thus, the injector lane with a lower minimum EGT offset during the sweep may be identified as having failed. Unlike the lane tests triggered by a low exhaust gas temperature, an inconclusive lane test due to out-of-range air-fuel ratio peak does not result in identifying an EGT sensor failure.
It will be apparent to those skilled in the art that various modifications and variations can be made to the structures and methodologies described herein. Thus, it should be understood that the invention is not limited to the subject matter discussed in the specification. Rather, the present invention is intended to cover modifications and variations.
This application is a U.S. national stage entry under 35 U.S.C. §371 from PCT International Application No. PCT/US2011/044650, filed Jul. 20, 2011, which claims priority to and the benefit of the filing date of U.S. Provisional Application No. 61/365,983, filed Jul. 20, 2010, to both of which this application claims the benefit of priority, and the entirety of the subject matter of both of which is incorporated herein by reference.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/US2011/044650 | 7/20/2011 | WO | 00 | 5/28/2013 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2012/012511 | 1/26/2012 | WO | A |
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