Engine operating system and method

Abstract

The present disclosure provides "engine operating systems and methods". Methods and systems are provided for estimating the maximum in-cylinder pressure of all engine cylinders while reducing the number of individual cylinders required for pressure sensing. Pressure sensing is performed on a single instrumented cylinder. For the remaining non-instrumented cylinders, a correction factor that depends on the engine speed is applied, which compensates for the variation in compression pressure between cylinders due to differences in intake valve closing.

Description

Technical Field

[0001] This specification generally relates to methods and systems for estimating maximum in-cylinder pressure in a vehicle engine to account for inter-cylinder variations in air charging dynamics and compression pressure. Background Art

[0002] Increasingly stringent engine emission standards require increasingly sophisticated engine control. One way to improve engine operation is to install pressure sensors in the engine cylinders. The pressure sensors can provide useful feedback information that can indicate engine combustion, engine performance, durability, and engine emissions in terms of combustion location, combustion quantity, and mass for each of the cylinders in which the pressure sensors are installed, as well as for the engine itself. The pressure sensors can be installed in each engine cylinder so that the controller can evaluate the manner in which the cylinders are operating. For example, if the mass fraction burn location of a single cylinder is delayed longer than desired, the engine fuel injection timing for that cylinder can be advanced to advance the crankshaft position of the mass fraction burn location during the engine cycle of a particular cylinder.

[0003] In some engine systems, the engine cost and computational power requirements for processing cylinder pressure sensor data can be reduced by relying on a single pressure sensor. For example, Fulton et al. disclose in US2017 / 0051700 an engine system in which a single pressure sensor is coupled to a single engine cylinder that provides the lowest root mean square error value. The cylinder pressure (e.g., maximum in-cylinder pressure) of a single engine cylinder is measured via the single sensor, while the corresponding pressure values of the remaining engine cylinders are inferred based on the measured pressure data using a model and the measured engine operating conditions.

[0004] However, the inventors herein have identified potential problems with the above methods. The modeled in-cylinder pressure values of the remaining engine cylinders can be error-prone. For example, the modeled values can deviate significantly from the measured cylinder pressure values (such as those obtained when a pressure sensor is installed in each cylinder). This can be mainly attributed to the inter-cylinder compression pressure variations caused by the air distribution (or dynamic charge air effect) and compression ratio differences between the instrumented cylinders and the non-instrumented cylinders. Additionally, engines typically maintain an engineering margin for peak cylinder pressure between the maximum limit and the calibration target. This engineering margin accounts for the variability between engines and between cylinders. Errors in peak cylinder pressure estimation can result in a larger margin to account for the variability between engines and between cylinders. This can in turn limit the peak torque that the engine can support.

[0005] The inventors have recognized that in a model, the in-cylinder pressure trace can be decomposed into a compression pressure component and a combustion pressure component. While the combustion pressure is related to the combustion event controlled by the fuel injection quantity and timing, the compression pressure is affected by air distribution and compression ratio. Although the combustion pressure reconstruction of an un-instrumented cylinder can be obtained by calibration via a crankshaft oscillation model that accounts for the cylinder-to-cylinder variation of the combustion event due to fuel injection quantity and timing changes, the compression pressure reconstruction cannot be achieved by similar means. For example, assuming that the compression pressure of an un-instrumented cylinder is the same as that of an instrumented cylinder, the cylinder-to-cylinder variation of air distribution and compression ratio is ignored. However, the actual cylinder-to-cylinder variation of the compression pressure varies with engine operating parameters such as engine speed. The compression pressure of each cylinder affects the subsequent pressure trace (including the combustion pressure) and ultimately the maximum in-cylinder pressure. Therefore, the model encounters errors in predicting the maximum in-cylinder pressure caused by the cylinder-to-cylinder variation of the compression pressure. In one example, if the compression pressure is not accurately known and a lower value is assumed for safety reasons, the amount of boost pressure that can be provided to the engine may be unnecessarily restricted, thereby limiting the engine torque output. On the other hand, if a pressure sensor is installed in each cylinder to reduce errors, the cost and complexity benefits of reducing component usage will be lost. Therefore, it may be difficult to balance the cost of pressure determination and the accuracy of pressure determination. SUMMARY OF THE INVENTION

[0006] In one example, the above problem can be at least partially solved by a method for an engine, the method including: measuring a maximum in-cylinder pressure in a first cylinder via a pressure sensor; and inferring a maximum in-cylinder pressure in a second cylinder based on a difference from the measured maximum cylinder pressure of the first cylinder, the difference being determined according to each of an intake valve closing timing and a cylinder identification of the second cylinder. In this way, the cylinder-to-cylinder pressure estimation variation can be reduced without the need to install a pressure sensor in each cylinder.

[0007] As an example, a multi-cylinder engine system can install a single pressure sensor in one of the engine cylinders (hereinafter referred to as the instrumented cylinder or the indicated cylinder), while the remaining engine cylinders do not include any installed sensors (hereinafter referred to as non-instrumented cylinders or non-indicated cylinders). During conditions where cylinder pressure estimation is required, such as for estimating fuel injection, boost limit, etc., the engine controller can use the output from the sensor to estimate the maximum in-cylinder pressure of the instrumented cylinder and infer the maximum in-cylinder pressure of the non-instrumented cylinders. Specifically, for a given non-instrumented cylinder, the controller can modify the measured in-cylinder pressure of the instrumented cylinder using one or more correction factors. As an example, the controller can apply a factor (e.g., α) that compensates for differences in fuel injection quantity and another factor (e.g., δ) that compensates for differences in fuel injection timing between cylinders. In addition, the controller can modify the measured in-cylinder pressure of the instrumented cylinder using yet another factor (e.g., β) that compensates for differences in air charge between cylinders based on differences in compression pressure between cylinders at intake valve closing (IVC). For a given cylinder, β can be mapped based on engine speed and torque setpoints. Additionally, β can be mapped based on the position and identification of the given non-instrumented cylinder. This is because even for two non-instrumented cylinders with the same IVC, the compression pressure can be different due to differences in ram air effects. In one example, the factor β can be mapped during a dynamic (dyno) test or while calibrating other engine parameters. Based on the mapped maximum in-cylinder pressures of the non-indicated cylinders and the indicated cylinder, the engine operating conditions can be adjusted. For example, the maximum allowable boost pressure can be adjusted to or within the maximum in-cylinder pressure. As another example, the EGR flow to the engine can be adjusted based on the maximum in-cylinder pressure.

[0008] In this way, the accuracy of maximum in-cylinder pressure estimation can be improved without the need to install additional pressure sensors in each cylinder. The technical effect of using correction factors that compensate for differences in compression pressure between cylinders is that the variation in air charge estimation between cylinders can be reduced. By more accurately estimating the maximum in-cylinder pressure of each cylinder, the boost pressure that can be provided to the engine can be determined more precisely. For example, a higher boost pressure can be provided to the engine. Similarly, a higher EGR flow can be provided. By precisely estimating the increased maximum in-cylinder pressure, the maximum torque output of the increased engine can be better supported.

[0009] It should be understood that the above Summary of the Invention is provided to introduce in a simplified form selected concepts that are further described in the Detailed Description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is uniquely defined by the claims that accompany the Detailed Description. Furthermore, the claimed subject matter is not limited to implementations that solve any of the disadvantages described above or in any part of this disclosure. Description of the Drawings

[0010] Figure 1 Shows a schematic diagram of an engine system.

[0011] Figure 2 Shows an example of an engine having a single instrumented cylinder and the remaining non-instrumented cylinders.

[0012] Figure 3 Shows a high-level flowchart of an exemplary method for estimating the maximum in-cylinder pressure of non-instrumented cylinders based on the measured maximum in-cylinder pressure of an instrumented cylinder and one or more correction factors.

[0013] Figure 4 Shows an exemplary contribution of compression pressure variations to the maximum in-cylinder pressure variations between cylinders.

[0014] Figure 5 Shows an exemplary variation of the calibration of correction factor β with engine speed and torque setpoints.

[0015] Figure 6 Shows an exemplary comparison of in-cylinder pressure trace estimates with and without application of correction factor β.

[0016] Figure 7 Shows an exemplary table comparing the maximum in-cylinder pressure estimates for all non-instrumented engine cylinders with and without application of correction factor β.

[0017] Figure 8 Shows exemplary maximum in-cylinder pressure calibration and validation results.

[0018] Figure 9 Shows the exemplary validation results of the p 最大 estimation model using transient dynamic data. Detailed Description

[0019] This specification relates to improving combustion within the cylinders of an internal combustion engine by accurately estimating the maximum in-cylinder pressure. Figure 1 Shows an exemplary cylinder of an internal combustion engine. Only one engine cylinder can be instrumented with a pressure sensor, while the remaining cylinders are non-instrumented, as Figure 2 shown. The engine controller can be configured to execute control routines (such as Figure 3 the exemplary routine of) to estimate the maximum in-cylinder pressure of each of the non-instrumented cylinders based on the output of the pressure sensor coupled to the instrumented cylinder and one or more correction factors. The correction factors can include factors that compensate for variations in fuel injection quantity, timing, and variations in compression pressure contributions( Figure 4)。A correction factor β calibrated relative to engine speed and torque can be used to compensate for the compression pressure variation ( Figure 5 ) to improve the accuracy of the maximum in-cylinder pressure estimation ( Figure 6 ). Exemplary estimation results are shown in the table of Figure 7 . The results are also verified using test data, as shown in Figures 8 to 9 .

[0020] Refer to Figure 1 , the internal combustion engine 10 includes a plurality of cylinders controlled by an electronic engine controller 12, and one of the cylinders is shown in Figure 1 . The engine 10 is included in a vehicle 5 configured for propulsion on a road.

[0021] The engine 10 includes a combustion chamber 30 and a cylinder wall 32. A piston 36 is located in the cylinder wall 32 and is connected to a crankshaft 40. The combustion chamber 30 is shown to communicate with an intake manifold 44 and an exhaust manifold 48 via corresponding intake valves 52 and exhaust valves 54. Each intake valve and exhaust valve can be operated by an intake cam 51 and an exhaust cam 53. The position of the intake cam 51 can be determined by an intake cam sensor 55. The position of the exhaust cam 53 can be determined by an exhaust cam sensor 57.

[0022] The fuel injector 66 is shown positioned to inject fuel directly into the combustion chamber 30, which is direct injection known to those skilled in the art. The fuel injector 66 delivers fuel in proportion to the pulse width from the controller 12. Fuel is delivered to the fuel injector 66 through a fuel system (not shown) including a fuel tank, a fuel pump, and a fuel rail (not shown). The fuel pressure delivered through the fuel system can be adjusted by changing a position valve that regulates the flow to the fuel pump (not shown). Additionally, a metering valve can be located in or near the fuel rail for closed-loop fuel control. The pump metering valve can also regulate the fuel flow to the fuel pump, thereby reducing the fuel pumped to the high-pressure fuel pump.

[0023] The intake manifold 44 is shown in communication with an optional electronic throttle 62 that adjusts the position of a throttle plate 64 to control the airflow from the intake boost chamber 46. A compressor 162 draws air from an intake port 42 for supply to the boost chamber 46. An exhaust rotary turbine 164 is coupled to the compressor 162 via a shaft 161. An intercooler 115 cools the air compressed by the compressor 162. The compressor speed can be adjusted by adjusting the position of a variable vane control 72 or a compressor bypass valve 158. In an alternative example, a wastegate 74 can replace the variable vane control 72 or, in addition to the variable vane control 72, the wastegate 74 can be used. The variable vane control 72 adjusts the position of variable geometry turbine vanes. When the vanes are in an open position, the exhaust can supply little energy to rotate the turbine 164. When the vanes are in a closed position, the exhaust can pass through the turbine 164 and apply an increased force on the turbine 164. Alternatively, the wastegate 74 allows the exhaust to flow around the turbine 164 to reduce the amount of energy supplied to the turbine. The compressor bypass valve 158 allows compressed air at the outlet of the compressor 162 to return to the input of the compressor 162. In this way, the efficiency of the compressor 162 can be reduced in order to affect the flow of the compressor 162 and reduce the intake manifold pressure.

[0024] In the depicted example, the engine 10 is a compression ignition engine in which combustion begins in the combustion chamber 30 as the piston 36 approaches top dead center on the compression stroke and the fuel is ignited via compression ignition. For example, the engine 10 can be a diesel engine.

[0025] In some examples, a universal exhaust gas oxygen (UEGO) sensor 126 can be coupled to the exhaust manifold 48 upstream of the emission device 70. In other examples, the UEGO sensor can be located downstream of one or more exhaust aftertreatment devices. Additionally, in some examples, the UEGO sensor can be replaced by a NOx sensor having both NOx and oxygen sensing elements.

[0026] At lower engine temperatures, a glow plug 68 can convert electrical energy into heat energy to raise the temperature in the combustion chamber 30. By raising the temperature of the combustion chamber 30, it is easier to ignite the cylinder air-fuel mixture via compression. The controller 12 adjusts the current and voltage supplied to the glow plug 68. In this way, the controller 12 can adjust the amount of electrical power supplied to the glow plug 68. The glow plug 68 protrudes into the cylinder and it can also include a pressure sensor integrated with the glow plug for determining the pressure within the combustion chamber 30. In an alternative example, such as when the engine is a spark ignition engine (such as a gasoline engine), the fuel can be ignited by a spark plug located at the top of the cylinder based on a spark advance signal received from the controller 12.

[0027] In one example, emission device 70 may include a particulate filter and a catalyst brick. In another example, multiple emission control devices may be used, each with multiple bricks. In one example, emission device 70 may include an oxidation catalyst. In other examples, the emission device may include a lean NOx trap or a selective catalytic reduction (SCR) and / or a diesel particulate filter (DPF).

[0028] Exhaust gas recirculation (EGR) may be provided to the engine via EGR valve 80. EGR valve 80 is a three-way valve that closes or allows exhaust gas to flow from downstream of exhaust device 70 to a location in the engine intake system upstream of compressor 162. In an alternate example, EGR may flow from upstream of turbine 164 to intake manifold 44. EGR may bypass EGR cooler 85, or alternatively, EGR may be cooled by passing through EGR cooler 85. In other examples, high pressure and low pressure EGR systems may be provided.

[0029] The controller 12 Figure 1 10. Controller 12 is shown as a conventional microcomputer including: microprocessor unit 102, input / output ports 104, read-only memory 106, random access memory 108, keep alive memory 110, and conventional data buses. In addition to those signals previously discussed, controller 12 is shown receiving various signals from sensors coupled to engine 10, including: engine coolant temperature (ECT) from temperature sensor 112 coupled to cooling sleeve 114; position sensor 134 coupled to accelerator pedal 130 for detecting accelerator position adjusted by driver 132; measurement of engine manifold pressure (MAP) from pressure sensor 121 coupled to intake manifold 44; boost pressure from pressure sensor 122; exhaust oxygen concentration from oxygen sensor 126; engine position sensor from Hall effect sensor 118 sensing crankshaft 40 position; measurement of air mass entering the engine from sensor 120 (e.g., hot wire air flow meter); and measurement of throttle position from sensor 58. Barometric pressure may also be sensed (sensor not shown) for processing by controller 12. In the exemplary aspect described herein, engine position sensor 118 produces a predetermined number of equally spaced pulses every revolution of the crankshaft from which engine speed (RPM) can be determined.

[0030] The controller 12 receives the Figure 1 The signals of various sensors are used Figure 1 Various actuators are used to adjust engine operation based on the received signals and instructions stored in the memory of the controller. For example, based on the torque demand as inferred based on the input from the pedal position sensor, the fuel injection amount and the boost pressure amount can be adjusted.

[0031] As described in reference Figure 2 in detail, one engine cylinder can be instrumented with a pressure sensor. The controller can estimate the maximum in-cylinder pressure of a single engine cylinder instrumented with an in-cylinder pressure sensor and adjust the combustion parameters of a given cylinder based on the estimated maximum in-cylinder pressure. Additionally, as described in reference Figure 3 in detail, the controller can model the maximum in-cylinder pressure for each of the remaining non-instrumented engine cylinders based on the output of a single pressure sensor and also based on a plurality of correction factors. Then, the combustion parameters of the remaining cylinders are adjusted based on the modeled maximum in-cylinder pressure values. Additionally, the EGR flow rate and boost pressure settings can vary based on the maximum in-cylinder pressure value of the cylinder. For example, a higher EGR flow rate or a higher boost pressure can be achieved considering a higher maximum in-cylinder pressure value.

[0032] During operation, each cylinder within engine 10 typically undergoes a four-stroke cycle: the cycle includes an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke. During the intake stroke, generally, the exhaust valve 54 is closed and the intake valve 52 is open. Air is introduced into the combustion chamber 30 via the intake manifold 44, and the piston 36 moves to the bottom of the cylinder to increase the volume within the combustion chamber 30. The position of the piston 36 near the bottom of the cylinder and at the end of its stroke (e.g., when the combustion chamber 30 is at its maximum volume) is generally referred to by those skilled in the art as bottom dead center (BDC). During the compression stroke, the intake valve 52 and the exhaust valve 54 are closed. The piston 36 moves toward the cylinder head to compress the air within the combustion chamber 30. The position of the piston 36 at the end of its stroke and closest to the cylinder head (e.g., when the combustion chamber 30 is at its minimum volume) is generally referred to by those skilled in the art as top dead center (TDC). During a process hereinafter referred to as injection, fuel is introduced into the combustion chamber. In some examples, fuel can be injected into the cylinder multiple times during a single cylinder cycle. During a process hereinafter referred to as ignition, the injected fuel is ignited by compression ignition, resulting in combustion. During the expansion stroke, the expanding gases push the piston 36 back to BDC. The crankshaft 40 converts the piston movement into rotational torque of the rotating shaft. Finally, during the exhaust stroke, the exhaust valve 54 opens to release the combusted air-fuel mixture into the exhaust manifold 48, and the piston returns to TDC. Note that the above is described only as an example, and the opening and / or closing timing of the intake and exhaust valves can vary, such as to provide positive or negative valve overlap, delayed intake valve closing, or various other examples. Additionally, in some examples, a two-stroke cycle can be used instead of a four-stroke cycle.

[0033] In some examples, vehicle 5 can be a hybrid vehicle having multiple torque sources available for one or more wheels 155. In other examples, vehicle 5 is a conventional vehicle having only an engine, or an electric vehicle having only an electric motor. In the example shown, vehicle 5 includes engine 10 and electric motor 152. Electric motor 152 can be a motor or a motor / generator. When one or more clutches 156 are engaged, the crankshaft 40 of engine 10 and electric motor 152 are connected to wheels 155 via transmission 154. In the depicted example, a first clutch 156 is disposed between crankshaft 40 and electric motor 152, and a second clutch 156 is disposed between electric motor 152 and transmission 154. Controller 12 can send signals to the actuators of each clutch 156 to engage or disengage the clutches so as to connect or disconnect crankshaft 40 from electric motor 152 and components connected to the electric motor, and / or to connect or disconnect electric motor 152 from transmission 154 and components connected to the transmission. Transmission 154 can be a gearbox, a planetary gear system, or another type of transmission. The powertrain can be configured in various ways, including as a parallel, series, or series-parallel hybrid vehicle.

[0034] Electric motor 152 receives electrical power from traction battery 60 to provide torque to wheels 155. Electric motor 152 can also operate as a generator to provide electrical power to charge battery 60, such as during a braking operation.

[0035] Now referring to Figure 2 , an exemplary engine 10 (such as Figure 1 engine 10) is shown, which shows the location of a cylinder pressure sensor for controlling combustion in engine 10. In this example, engine 10 includes eight cylinders having combustion chambers 30, which are consecutively numbered from 1 - 8. A single pressure sensor 68 is shown mounted in an engine cylinder. In particular, the first cylinder is instrumented with pressure sensor 68. Herein, the cylinder in which the pressure sensor is installed is referred to as the indicated cylinder or the instrumented cylinder. None of the remaining engine cylinders (numbered 2 through 8) have a pressure sensor installed. These remaining cylinders are referred to herein as non-indicated or non-instrumented cylinders.

[0036] The cylinder pressure feedback provided by pressure sensor 68 located in cylinder number 1 is the basis for controlling the fuel injection timing and fuel injection quantity of cylinders 1 - 8 and for adjusting combustion at various engine speeds and loads. For example, the maximum in-cylinder pressure of cylinder 1 can be measured based on the cylinder pressure feedback provided by pressure sensor 68. This measurement value is sent to controller 12 and stored in the memory of controller 12. Then, controller 12 can be based on the maximum in-cylinder pressure of cylinder 1 and also based on a plurality of correction factors (such as Figure 3inferred or modeled for the maximum in-cylinder pressure of cylinders 2-8 (as described in detail in the location).

[0037] In this way, Figures 1 to 2 a component implements an engine system that includes: a first cylinder instrumented with an in-cylinder pressure sensor; a second non-instrumented cylinder; an engine speed sensor coupled to the engine crankshaft; and a controller having computer-readable instructions stored on a non-transitory memory for the following operations: measuring a maximum in-cylinder pressure value of the first cylinder via the pressure sensor; calculating a compression pressure correction factor based on each of the position of the second cylinder relative to the first cylinder on the engine block, the engine speed, and the intake valve closing of the second cylinder relative to the first cylinder; and inferring a maximum in-cylinder pressure value of the second cylinder based on the measured maximum in-cylinder pressure value of the first cylinder and the calculated compression pressure correction factor. Additionally or alternatively, the system may further include a compressor for providing boost air charge to the engine system, and the controller may include additional instructions for the following operation: limiting the boost pressure output by the compressor based on the inferred maximum in-cylinder pressure value, where the maximum allowable boost pressure increases as the inferred maximum in-cylinder pressure value increases. In some examples, the system may further include an EGR passage for recirculating exhaust from the exhaust port to the intake port of the engine system, the EGR passage including a valve, and the controller may include additional instructions for the following operation: limiting the EGR flow based on the inferred maximum in-cylinder pressure value, where the maximum allowable EGR flow increases as the inferred maximum in-cylinder pressure value increases. Additionally, the controller may calculate the compression pressure correction factor by estimating the ram air received in the second cylinder relative to the first cylinder based on the position of the second cylinder relative to the first cylinder on the engine block, and adjust the correction factor based on the estimated ram air difference between the second cylinder and the first cylinder. In one example, adjusting the correction factor includes increasing the correction factor as the estimated ram air difference increases. In another example, adjusting the correction factor includes decreasing the correction factor as the estimated ram air difference increases.

[0038] In this way, combustion in all engine cylinders is controlled based on cylinder pressure data observed by a single pressure sensor during the cylinder cycle. By reducing the need to install pressure sensors in each cylinder, component cost and complexity are reduced. At the same time, by relying on calibrated correction factors to use the data captured at a single instrumented cylinder to infer the pressure value of a non-instrumented cylinder, the accuracy of pressure estimation is not impaired. Therefore, cylinder combustion can be better controlled.

[0039] Now turning to Figure 3 , shows the maximum in-cylinder pressure value (p for each cylinder of the engine 最大) exemplary method 300 and adjust engine combustion accordingly. This method enables accurate determination of the p of all engine cylinders when relying on a single installed cylinder pressure sensor 最大 . The instructions for performing method 300 and the remaining methods included herein can be executed by a controller based on instructions stored in the controller's memory and in conjunction with signals received from sensors of the engine system, such as those referenced above Figure 1 and Figure 2 the sensors described. According to the methods described below, the controller can employ engine actuators of the engine system to adjust engine operation.

[0040] At 302, engine operating conditions can be estimated and / or measured. For example, engine speed, engine temperature, boost pressure, exhaust temperature, exhaust air-fuel ratio, ambient conditions (such as ambient pressure, temperature, and humidity), MAP, MAF, etc. can be measured. At 304, it can be determined whether a maximum in-cylinder pressure calibration condition has been met. For example, it can be determined whether a threshold duration or distance of vehicle (or engine) operation has elapsed since the last estimation of the maximum in-cylinder pressure of all engine cylinders. As another example, if one or more engine operating parameters, such as engine coolant temperature, fuel injection quantity, and engine speed, meet the enabling conditions for pressure measurement and / or maximum in-cylinder pressure (p 最大 ) model execution, the calibration condition can be considered to be met.

[0041] If the calibration condition is not met, then at 306, the method includes retrieving the last estimated value of the maximum in-cylinder pressure or p 最大 for each of the engine cylinders. Then, at 320, one or more engine operating parameters and their calibrations can be adjusted based on the retrieved values. For example, one or more of boost pressure limit, EGR limit, fuel injection (quantity and timing), etc. can be calculated based on the p 最大 value for each cylinder.

[0042] Returning to 304, if the calibration condition is met, then at 308, the method includes measuring the in-cylinder pressure of the indicated or instrumented cylinder via an in-cylinder pressure sensor (ICPS) installed therein. For example, sensor output can be collected. At 310, the method includes determining the p 最大 of the indicated cylinder. For example, the controller can select the maximum value in the measured in-cylinder pressure trace.

[0043] At 312, the method includes determining a correction factor α(α) for each of the remaining non-indicated or non-instrumented cylinders. The correction factor α can be a correction for compensating the fuel injection quantity. At 314, the method includes determining a correction factor δ(δ) for each of the non-indicated or non-instrumented cylinders. The correction factor δ can be a correction for compensating the fuel injection timing.

[0044] At 316, the method includes calculating a correction factor β(β) for each of the non-indicated or non-instrumented cylinders. The correction factor β can be based on the cylinder intake valve closing (IVC) timing and can account for differences in ram air effects. In particular, these differences can result in variations in the compression pressure between cylinders, which in turn affect the p 最大 value.

[0045] At 317, the method includes reconstructing the non-indicated cylinder pressure traces based on the indicated cylinder pressure traces and also based on the correction factors α, β, and δ. At 318, the method includes calculating a p 最大 for each of the non-indicated cylinders based on the reconstructed in-cylinder pressure traces.

[0046] Then, at 320, one or more engine operating parameters and their calibrations can be adjusted based on the determined values. For example, one or more of the boost pressure limit, EGR limit, fuel injection (quantity and timing), etc. can be calculated based on the p 最大 value for each cylinder. In one example, as the average maximum in-cylinder pressure value on the engine cylinders becomes larger, the boost limit can be increased and a higher boost pressure can be enabled. Similarly, the EGR limit can be increased and a higher EGR flow can be enabled. As another example, the fuel injection quantity can be increased without causing a rich air-fuel ratio shift.

[0047] When using a single ICPS to model the cylinder pressure traces to predict the in-cylinder pressure traces of other cylinders, an error between the predicted and measured in-cylinder pressure traces may be encountered. The root cause of the error is determined to be the variation in the compression pressure between cylinders due to the differences in air distribution and compression ratio between the instrumented and non-instrumented cylinders.

[0048] In this model, the in-cylinder pressure trace is decomposed into a compression pressure and a combustion pressure trace, as shown in Figure 4 reference. While the combustion pressure is related to the combustion event controlled by the fuel injection quantity and timing, the compression pressure is affected by the air distribution and compression ratio.

[0049] Briefly turning to Figure 4, the map 400 depicts at curve 402 the trace of the total in-cylinder pressure of all engine cylinders instrumented with corresponding pressure sensors. Then, the total in-cylinder pressure is decomposed into a component combustion pressure (cmb) trace at curve 406 and a compression pressure (cmp) trace at curve 404. For a given cylinder, the measured in-cylinder pressure trace (p cyl (θ)) can be determined as:

[0050] p cyl (θ) = p cmp (θ) + p cmb (θ), where θ is the crank angle.

[0051] As can be seen from Figure 4 , the variation in maximum in-cylinder pressure among cylinders is maintained due to changes in compression pressure rather than combustion pressure. The combustion pressure is controlled by combustion related to fuel injection quantity and timing. At a given engine operating point, the variation in fuel injection among cylinders is less than the variation in air charge that affects the compression pressure change.

[0052] For the reconstruction of the combustion pressure of non-indicating cylinders, it is assumed that the shape of the combustion pressure will be the same as that of the indicating cylinders, and the combustion pressure can be corrected by a crankshaft oscillation model to account for the cylinder-to-cylinder variation in combustion events due to fuel injection quantity and timing changes. Initially, it is assumed that the compression pressure of non-indicating cylinders is the same as that of indicating cylinders, ignoring the cylinder-to-cylinder variation in air distribution and compression ratio.

[0053] However, the actual cylinder-to-cylinder variation in compression pressure increases with increasing engine speed, as indicated at Figure 5 . The compression pressure of each cylinder affects the subsequent pressure trace (combustion pressure), and ultimately affects the maximum in-cylinder pressure. Therefore, if the model does not account for the cylinder-to-cylinder variation in compression pressure, the model will encounter errors in predicting the maximum in-cylinder pressure.

[0054] In one example, with the compression pressure change ignored, the error can have a magnitude of up to 2 bar RMSE (root mean square error) across the full range in the low engine speed range and up to 9 bar across the full range at higher engine speeds. An error of this magnitude may prevent the use of cylinder pressure trace estimation to predict the maximum cylinder pressure.

[0055] As described above, the main sources of variation in in-cylinder pressure among cylinders are attributed to timing (δ), fuel quantity (α), and pressure at intake valve closure (β), as indicated by the following equation:

[0056]

[0057] where p cmp,0 and pcmb,0 Refer to the compression pressure and combustion pressure respectively, and are known based on the ICPS measurements in the indicated cylinder.

[0058] The correction factor δ (δ i ) for a given cylinder is determined as

[0059] δ i = CA50 i - CA500

[0060] where CA500 is the ICPS measurement in the indicated cylinder, and CA50 i is the output of the crankshaft oscillation model.

[0061] The correction factor α (α i ) for a given cylinder is determined by the following equation:

[0062] trq Inr，i = ∫p cyl，i dV = ∫p cmp，0 dV + α i ∫p cmb，0 (θ - δ i )dV

[0063] where trq Inr，i is a known value output from the crankshaft oscillation model, p cmp,0 and p cmb,0 are known values from the ICPS measurements of the indicated cylinder, δ is determined by CA50 i - CA500, and dV is a given value. Thus, α can be calculated.

[0064] The correction factor β (β i ) for a given cylinder is then determined as:

[0065]

[0066] Then, the maximum in-cylinder pressure of a given cylinder is determined as:

[0067]

[0068] Specifically, the pressure trace of each non-indicated cylinder can be reconstructed based on the indicated cylinder pressure trace and also based on the correction factors α, β, and δ. Then, the maximum in-cylinder pressure of the non-indicated cylinder can be predicted based on the reconstructed pressure trace.

[0069] A single ICPS measurement and a crankshaft oscillation model can be used to calculate factors α and δ. Additionally, factor β can be applied to account for differences in air charge between cylinders. β is primarily a function of engine speed and engine load and is calibrated for the engine family. The addition of factor β improves the estimation of the maximum in-cylinder pressure from approximately 5 bar to approximately 1.5 bar.

[0070] Reference Figure 5 Curves 500 - 506 of Figure 5 show an exemplary β calibration. In particular, Figure 5 at curves 500 - 506, β patterns are shown for four different engine speeds and various torque set points per cylinder. As Figure 5 shown, β varies with engine speed and torque set point, and the β value increases as the engine speed increases. Thus, β can be approximated as a function of engine speed and torque set point. In each case, the correction factor β, which compensates for errors encountered due to compression ratio and air distribution effects, can be defined as the ratio of the maximum compression pressure of an indicated cylinder to the maximum compression pressure of a non-indicated cylinder.

[0071] In a further example, β can be estimated in real time based on engine operating conditions such as intake manifold pressure. The engine controller can map the factor β for each cylinder based on engine speed (or engine speed and torque set point). This correction is then referred to as β i , where the subscript i refers to the cylinder number.

[0072] After analyzing the data, it was found that the inter-cylinder variation in compression pressure increases with increasing engine speed, and even with a fixed commanded fuel injection quantity and timing under a given engine operating condition, the maximum in-cylinder pressure variation is mainly affected by the compression pressure variation. Since the fuel injection quantity and timing variations are relatively small compared to the compression pressure variation under normal conditions, the combustion pressure traces of each cylinder have similar magnitudes and phases to each other under a given engine operating condition.

[0073] The air distribution variation, which is the root cause of the in-cylinder pressure variation between cylinders during compression, is mainly caused by the ram air effect (air path dynamics), and the ram air effect is highly correlated with the engine geometry. For example, the amount of ram air ingested into a given cylinder can be a function of the cylinder's position along the engine block, and further reference is made to the intake flow path, intake port, or intake plenum position. Once the engine geometry design is fixed, the ram air effect will have a pattern that depends on the engine speed (or engine speed and torque setpoint), which means that the correction factor β can be configured as a map according to the engine speed (or engine speed and torque setpoint). When a single pressure sensor is installed in the indicated cylinder, the corresponding β value of the non-indicated cylinder (the ratio of the maximum compression pressure of the indicated cylinder to the maximum compression pressure of the non-indicated cylinder) can also be predefined through calibration using typical dynamic mapping data. Additionally, after a simple calibration process, this correction factor can be easily applied to different engines.

[0074] In this way, the controller can measure the maximum in-cylinder pressure in the first cylinder via the pressure sensor; then infer the maximum in-cylinder pressure in the second cylinder based on the difference from the measured maximum cylinder pressure of the first cylinder. This difference is determined according to each of the intake valve closing timing and cylinder identification of the second cylinder. In one example, the difference determined according to the cylinder identification includes the difference determined according to one or more of the cylinder's position on the engine block, the cylinder's position relative to the intake plenum or intake flow path, and the engine firing order. For example, it can be determined whether the cylinder is closer to or farther from the intake plenum, such that the ram air effect on the first cylinder can be better estimated and considered relative to the ram air effect on the second cylinder. Therefore, the difference determined according to the cylinder identification is used to infer the difference caused by the ram air effect on the second cylinder relative to the first cylinder. In this example, the pressure sensor is installed in the first cylinder (also referred to as the instrumented cylinder or indicated cylinder) and not in the second cylinder (also referred to as the non-instrumented cylinder or non-indicated cylinder). The difference determined according to the intake valve closing timing can also include applying a correction factor based on the engine speed variation. This is because the difference determined according to the intake valve closing (IVC) timing includes the difference in compression pressure between the second cylinder and the first cylinder caused by the difference in IVC timing. This inference can also be based on the difference in combustion pressure between the second cylinder and the first cylinder, which is estimated according to the fuel injection amount and fuel injection timing.

[0075] In some examples, the controller may also adjust the operating parameters of the second cylinder to maintain the actual cylinder pressure at or below the maximum in-cylinder pressure of the second cylinder. For example, the controller may retard the spark timing to the limit based on the maximum in-cylinder pressure. As another example, the controller may limit the boost pressure based on the maximum in-cylinder pressure, thereby allowing a higher absolute boost pressure and a higher engine output. As yet another example, the controller may limit the exhaust gas recirculation flow based on the maximum in-cylinder pressure, thereby allowing a higher absolute amount of EGR flow to be provided.

[0076] Figure 6 An exemplary comparison of in-cylinder pressure traces with and without β correction is shown. As shown at the map 600, the comparison of curve 604 (modeled value without β correction) and curve 602 (modeled value with β correction) shows a significant variation 608, corresponding to β herein. Additionally, the β-corrected modeled pressure trace of curve 602 better aligns with the actual measured pressure trace curve 606 of the corresponding cylinder equipped with a pressure sensor. In other words, with β correction, the reconstructed pressure trace will predict p with higher accuracy and reliability. 最大 。

[0077] The model with the correction factor β is also validated using various steady-state and transient dynamic data sets. As Figures 7 to 9 shown, the modeling method is capable of predicting the minimum in-cylinder pressure with an RMSE of less than 2.5 bar over the full engine operating range.

[0078] Figure 7 An exemplary p 最大 estimation comparison between the data collected with (Table 702) and without (Table 700) β correction using fuel sweep and main injection timing (phiMI) sweep data is shown. As shown, β correction improves the p 最大 estimation, especially at higher engine speed conditions. The p 最大 estimation accuracy improves from an RMSE of 3.1 bar to an RMSE of 1.8 bar when using fuel sweep data, and from an RMSE of 5.1 bar to an RMSE of 1.8 bar when using phiMI sweep data.

[0079] For the fuel and phiMI sweep tests, the fuel quantity or main injection timing deviation of one cylinder is 4 different values compared to the baseline condition at a given engine operating point, and the fuel quantity and injection timing of the remaining cylinders remain the same as the baseline condition. In Figure 7 the data set shown, the eight-cylinder fuel and phiMI sweep tests are performed at 42 different engine operating points.

[0080] Figure 8The validation results using the steady-state data set are depicted in Tables 800, 802. The model was validated using various data sets, and the p 最大 estimation accuracy has an RMSE of less than 2.5 bar over the full engine operating range. For the EGR sweep test, the EGR level was changed to 3 or 5 offset levels compared to the baseline condition at each engine operating point. In the Figure 8 data set shown, 120 engine operating points were used for the EGR sweep.

[0081] Figure 9 The validation results using the transient dynamic test data are depicted in Curves 900 - 905. The model was also validated using transient dynamic test data, which is the HDDT (Heavy-Duty Diesel Truck) cycle. The model predicts p 最大 .

[0082] In one example, the controller may measure the in-cylinder pressure indicative of a cylinder and then determine the maximum in-cylinder pressure of non-indicated cylinders based on calculations using a look-up table, where the inputs to the look-up table are the in-cylinder pressure of the indicated cylinder and the current engine speed and load. The generated output includes different correction factors. These factors are then used in calculations, models, equations, or algorithms to determine the maximum in-cylinder pressure for each of the non-indicated cylinders. For example, the controller may measure the cylinder pressure of a cylinder instrumented with a pressure sensor; then, for each of the remaining non-instrumented cylinders, the controller may model the cylinder pressure based on the measured cylinder pressure and the differences from the measured cylinder pressure, which are determined based on each of the changes in compression pressure and ram air between the cylinders. Thereafter, the controller may adjust the engine boost pressure based on the modeled cylinder pressures. The controller may also estimate the change in compression pressure by applying a correction factor that depends on engine speed to the measured cylinder pressure. Additionally, the controller may estimate the change in ram air between the engine cylinders based on the intake valve closing timing of each of the remaining non-instrumented cylinders relative to the instrumented cylinder. The change in ram air may be further estimated based on the position of the cylinder along the engine block and the firing order. This accounts for the change in compression pressure. The modeled cylinder pressure may also be based on the change in combustion pressure, which is estimated based on the fuel injection quantity and fuel injection timing of each of the remaining non-instrumented cylinders relative to the instrumented cylinder. In this way, air charge estimation is improved while reducing the number of pressure sensors required and without compromising accuracy. By sensing the maximum in-cylinder pressure in one cylinder and inferring values in the remaining cylinders by applying various correction factors, the contributions of the differences in combustion pressure and compression pressure between the cylinders can be better accounted for. By considering the differences in IVC timing between the cylinders, the differences in compression pressure between the cylinders can be accurately estimated. By considering the differences in cylinder positions, the different ram air effects experienced in each cylinder can be better estimated. By accurately estimating the maximum in-cylinder pressure for each cylinder, the engine pressure limits can be updated, allowing for more optimized scheduling of boost and EGR. Therefore, engine performance can be improved while supporting higher engine output.

[0083] An exemplary method includes: measuring a maximum in-cylinder pressure in a first cylinder via a pressure sensor; and inferring a maximum in-cylinder pressure in a second cylinder based on a difference from the measured maximum cylinder pressure of the first cylinder, the difference being determined according to each of an intake valve closing timing of the second cylinder and a cylinder identification. In the foregoing example, additionally or alternatively, the difference determined according to the cylinder identification includes a difference determined according to one or more of a position of the cylinder on an engine block, a position of the cylinder relative to an intake chamber or an intake flow passage, and an engine ignition order. In any or all of the foregoing examples, additionally or alternatively, the difference determined according to the cylinder identification includes a difference caused by a ram air effect on the second cylinder relative to the first cylinder. In any or all of the foregoing examples, additionally or alternatively, the pressure sensor is installed in the first cylinder and not in the second cylinder. In any or all of the foregoing examples, additionally or alternatively, the difference determined according to the intake valve closing timing includes applying a correction factor based on an engine speed change. In any or all of the foregoing examples, additionally or alternatively, the difference determined according to the intake valve closing timing includes a difference in compression pressure between the second cylinder and the first cylinder. In any or all of the foregoing examples, additionally or alternatively, the inference is further based on a difference in combustion pressure between the second cylinder and the first cylinder, the difference in combustion pressure being estimated according to a fuel injection amount and a fuel injection timing. In any or all of the foregoing examples, additionally or alternatively, the method further includes adjusting an operating parameter of the second cylinder to maintain an actual cylinder pressure at or below the maximum in-cylinder pressure of the second cylinder. In any or all of the foregoing examples, additionally or alternatively, the adjustment includes one or more of the following: retarding spark timing to a limit based on the maximum in-cylinder pressure, limiting boost pressure based on the maximum in-cylinder pressure, and limiting exhaust gas recirculation flow based on the maximum in-cylinder pressure.

[0084] Another exemplary engine method includes: measuring the cylinder pressure of a cylinder instrumented with a pressure sensor; for each of the remaining non-instrumented cylinders, modeling the cylinder pressure based on the measured cylinder pressure and a difference from the measured cylinder pressure, the difference being determined based on each of the compression pressure and ram air variations between cylinders; and adjusting the engine boost pressure based on the modeled cylinder pressures. In the foregoing example, additionally or alternatively, the method further includes estimating a change in compression pressure by applying a correction factor dependent on engine speed to the measured cylinder pressure. In any or all of the foregoing examples, additionally or alternatively, the method further includes estimating a change in ram air based on the intake valve closing timing of each of the remaining non-instrumented cylinders relative to the instrumented cylinder. In any or all of the foregoing examples, additionally or alternatively, the estimated change in ram air is further based on the position of the cylinder along the engine block and the firing order. In any or all of the foregoing examples, additionally or alternatively, the modeled cylinder pressure may further be based on a change in combustion pressure, the change in combustion pressure being estimated based on the fuel injection quantity and fuel injection timing of each of the remaining non-instrumented cylinders relative to the instrumented cylinder.

[0085] Another exemplary engine system includes: a first cylinder instrumented with an in-cylinder pressure sensor; a second non-instrumented cylinder; an engine speed sensor coupled to the engine crankshaft; and a controller having computer-readable instructions stored on a non-transitory memory for the following operations: measuring a maximum in-cylinder pressure value of the first cylinder via the pressure sensor; calculating a compression pressure correction factor based on each of the position of the second cylinder relative to the first cylinder on the engine block, the engine speed, and the intake valve closing of the second cylinder relative to the first cylinder; and inferring a maximum in-cylinder pressure value of the second cylinder based on the measured maximum in-cylinder pressure value of the first cylinder and the calculated compression pressure correction factor. In the foregoing example, additionally or alternatively, the system further includes a compressor for providing boosted air charge to the engine system, and the controller includes additional instructions for the following operation: limiting the boost pressure output by the compressor based on the inferred maximum in-cylinder pressure value, where the maximum allowable boost pressure increases as the inferred maximum in-cylinder pressure value increases. In any or all of the foregoing examples, additionally or alternatively, the system further includes an EGR passage for recirculating exhaust from an exhaust port to an intake port of the engine system, the EGR passage including a valve, and the controller includes additional instructions for the following operation: limiting the EGR flow based on the inferred maximum in-cylinder pressure value, where the maximum allowable EGR flow increases as the inferred maximum in-cylinder pressure value increases. In any or all of the foregoing examples, additionally or alternatively, calculating the compression pressure correction factor includes estimating ram air received in the second cylinder relative to the first cylinder based on the position of the second cylinder relative to the first cylinder on the engine block, and adjusting the correction factor based on the estimated ram air difference between the second cylinder and the first cylinder. In any or all of the foregoing examples, additionally or alternatively, adjusting the correction factor includes increasing the correction factor as the estimated ram air difference increases. In any or all of the foregoing examples, additionally or alternatively, adjusting the correction factor includes decreasing the correction factor as the estimated ram air difference increases.

[0086] In another representation, the engine system is coupled in a hybrid vehicle system. In yet another representation, the engine system is coupled in an autonomous vehicle system.

[0087] Note that the exemplary control and estimation routines included herein can be used with a variety of engine and / or vehicle system configurations. The control methods and routines disclosed herein can be stored as executable instructions in a non-transitory memory and can be executed by a control system including a controller in conjunction with various sensors, actuators, and other engine hardware. The specific routines described herein can represent one or more of any number of processing strategies, such as event-driven, interrupt-driven, multitasking, multithreaded, etc. Accordingly, the various acts, operations, and / or functions shown can be executed in the order shown, executed in parallel, or omitted in some cases. Similarly, the order of processing is not necessarily required to achieve the features and advantages of the exemplary embodiments described herein, but is provided for ease of illustration and description. One or more of the acts, operations, and / or functions shown can be repeatedly executed according to the particular strategy used. Further, the acts, operations, and / or functions described can graphically represent code to be programmed into the non-transitory memory of a computer-readable storage medium for an engine control system, where the described acts are executed by executing the instructions in a system including various engine hardware components in conjunction with an electronic controller.

[0088] It should be understood that the configurations and routines disclosed herein are exemplary in nature and these specific embodiments should not be considered limiting in any sense as many variations are possible. For example, the above techniques can be applied to V-6, I-4, I-6, V-12, opposed 4, and other engine types. The subject matter of the present disclosure includes all novel and non-obvious combinations and sub-combinations of the various systems and configurations and other features, functions, and / or properties disclosed herein.

[0089] The appended claims particularly point out certain combinations and sub-combinations regarded as novel and non-obvious. These claims can refer to "a" element or "a first" element or the equivalent thereof. These claims are to be understood to include the combination of one or more such elements, neither requiring nor precluding the combination of two or more such elements. Other combinations and sub-combinations of the disclosed features, functions, elements, and / or properties can be claimed by modifying the present claims or presenting new claims in this or a related application. These claims, whether broader, narrower, the same, or different in scope from the original claims, are also regarded as included within the subject matter of the present disclosure.

[0090] According to the present invention, a method includes: measuring a maximum in-cylinder pressure in a first cylinder via a pressure sensor; and inferring a maximum in-cylinder pressure in a second cylinder based on a difference from the measured maximum cylinder pressure of the first cylinder, the difference being determined based on each of an intake valve closing timing and a cylinder identification of the second cylinder.

[0091] According to one embodiment, the differences determined according to the cylinder identification include differences determined according to one or more of the position of the cylinder on the engine block, the position of the cylinder relative to the intake chamber or the intake air flow passage, and the engine ignition sequence.

[0092] According to one embodiment, the differences determined according to the cylinder identification include differences caused by the ram air effect on the second cylinder relative to the first cylinder.

[0093] According to one embodiment, a pressure sensor is installed in the first cylinder and not in the second cylinder.

[0094] According to one embodiment, the differences determined according to the intake valve closing timing include applying a correction factor based on the change in engine speed.

[0095] According to one embodiment, the differences determined according to the intake valve closing timing include the difference in compression pressure between the second cylinder and the first cylinder.

[0096] According to one embodiment, the inference is further based on the difference in combustion pressure between the second cylinder and the first cylinder, and the difference in combustion pressure is estimated according to the fuel injection amount and the fuel injection timing.

[0097] According to one embodiment, the present invention is further characterized in that: adjusting the operating parameters of the second cylinder to maintain the actual cylinder pressure at or below the maximum in-cylinder pressure of the second cylinder.

[0098] According to one embodiment, the adjustment includes one or more of the following: retarding the spark timing to the limit based on the maximum in-cylinder pressure, limiting the boost pressure based on the maximum in-cylinder pressure, and limiting the exhaust gas recirculation flow based on the maximum in-cylinder pressure.

[0099] According to the present invention, an engine method includes: measuring the cylinder pressure of a cylinder instrumented with a pressure sensor; for each of the remaining non-instrumented cylinders, modeling the cylinder pressure based on the measured cylinder pressure and the difference from the measured cylinder pressure, the difference being determined based on each of the change in compression pressure and ram air between the cylinders; and adjusting the engine boost pressure based on the modeled cylinder pressure.

[0100] According to one embodiment, the present invention is further characterized in that: estimating the change in compression pressure by applying a correction factor dependent on the engine speed to the measured cylinder pressure.

[0101] According to one embodiment, the present invention is further characterized in that: estimating the change in ram air based on the intake valve closing timing of each of the remaining non-instrumented cylinders relative to the instrumented cylinder.

[0102] According to one embodiment, the estimation of the ram air variation is also based on the position of the cylinder along the engine block and the firing order.

[0103] According to one embodiment, the modeled cylinder pressure can also be based on a variation in combustion pressure, which is estimated based on the fuel injection quantity and fuel injection timing of each of the remaining non-instrumented cylinders relative to the instrumented cylinder.

[0104] According to the present invention, there is provided an engine system having: a first cylinder instrumented with an in-cylinder pressure sensor; a second non-instrumented cylinder; an engine speed sensor coupled to the engine crankshaft; and a controller having computer-readable instructions stored on a non-transitory memory for: measuring, via the pressure sensor, a maximum in-cylinder pressure value of the first cylinder; calculating a compression pressure correction factor based on the position of the second cylinder on the engine block relative to the first cylinder, the engine speed, and the intake valve closing of the second cylinder relative to the first cylinder; and inferring a maximum in-cylinder pressure value of the second cylinder based on the measured maximum in-cylinder pressure value of the first cylinder and the calculated compression pressure correction factor.

[0105] According to one embodiment, the present invention is further characterized by: a compressor for supplying boost air charge to the engine system, wherein the controller includes additional instructions for: limiting the boost pressure output by the compressor based on the inferred maximum in-cylinder pressure value, and the maximum allowable boost pressure increases as the inferred maximum in-cylinder pressure value increases.

[0106] According to one embodiment, the present invention is further characterized by: an EGR passage for recirculating exhaust from an exhaust port to an intake port of the engine system, the EGR passage including a valve, wherein the controller includes additional instructions for: limiting the EGR flow based on the inferred maximum in-cylinder pressure value, and the maximum allowable EGR flow increases as the inferred maximum in-cylinder pressure value increases.

[0107] According to one embodiment, calculating the compression pressure correction factor includes estimating the ram air received by the second cylinder relative to the first cylinder based on the position of the second cylinder on the engine block relative to the first cylinder, and adjusting the correction factor based on the estimated ram air difference between the second cylinder and the first cylinder.

[0108] According to one embodiment, adjusting the correction factor includes increasing the correction factor as the estimated ram air difference increases.

[0109] According to one embodiment, adjusting the correction factor includes decreasing the correction factor as the estimated ram air difference increases.

Claims

1. A method for an engine, comprising: Measuring a maximum in-cylinder pressure in a first cylinder via a pressure sensor; And Inferring a maximum in-cylinder pressure in the second cylinder based on a difference between the first cylinder and the second cylinder and the measured maximum cylinder pressure of the first cylinder, the difference being determined according to each of an intake valve closing timing and a cylinder identification of the second cylinder.

2. The method according to claim 1, wherein the difference determined according to the cylinder identification includes the difference determined according to one or more of a position of the cylinder on an engine block, a position of the cylinder relative to an intake chamber or an intake flow passage, and an engine ignition order.

3. The method according to claim 1, wherein the difference determined according to the cylinder identification includes a difference caused by a ram air effect on the second cylinder relative to the first cylinder, wherein the ram air effect is related to a geometry of the engine.

4. The method according to claim 1, wherein the pressure sensor is installed in the first cylinder and not in the second cylinder.

5. The method according to claim 1, wherein the difference determined according to the intake valve closing timing includes applying a correction factor based on a change in engine speed.

6. The method according to claim 1, wherein the difference determined according to the intake valve closing timing includes a difference in compression pressure between the second cylinder and the first cylinder.

7. The method according to claim 1, wherein the inference is further based on a difference in combustion pressure between the second cylinder and the first cylinder, the difference in combustion pressure being estimated according to a fuel injection amount and a fuel injection timing.

8. The method according to claim 1, further comprising: Adjusting an operating parameter of the second cylinder to maintain an actual cylinder pressure at or below the maximum in-cylinder pressure of the second cylinder.

9. The method according to claim 8, wherein the adjustment includes one or more of the following: retarding a spark timing to a limit based on the maximum in-cylinder pressure, limiting a boost pressure based on the maximum in-cylinder pressure, and limiting an exhaust gas recirculation flow based on the maximum in-cylinder pressure.

10. An engine system, comprising: A first cylinder instrumented with an in-cylinder pressure sensor; A non-instrumented second cylinder; An engine speed sensor coupled to an engine crankshaft; And A controller having computer-readable instructions stored on a non-transitory memory for the following operations: Measuring a maximum in-cylinder pressure value of the first cylinder via the pressure sensor; Calculating a compression pressure correction factor based on each of a position of the second cylinder on an engine block relative to the first cylinder, an engine speed, and an intake valve closing of the second cylinder relative to the first cylinder; and Inferring a maximum in-cylinder pressure value of the second cylinder based on the measured maximum in-cylinder pressure value of the first cylinder and the calculated compression pressure correction factor.

11. The system according to claim 10, further comprising a compressor for supplying boost air charge to the engine system, wherein the controller further includes instructions for the following operations: The boost pressure output by the compressor is limited based on the inferred maximum in-cylinder pressure value, and the maximum allowable boost pressure increases as the inferred maximum in-cylinder pressure value increases.

12. The system according to claim 10, further comprising an EGR passage for recirculating exhaust gas from an exhaust port to an intake port of the engine system, the EGR passage including a valve, wherein the controller includes additional instructions for: limiting the EGR flow rate based on the inferred maximum in-cylinder pressure value, and the maximum allowable EGR flow rate increases as the inferred maximum in-cylinder pressure value increases.

13. The system according to claim 10, wherein calculating the compression pressure correction factor comprises: estimating the ram air received in the second cylinder relative to the first cylinder based on the position of the second cylinder on the engine block relative to the first cylinder, and adjusting the correction factor based on the estimated ram air difference between the second cylinder and the first cylinder.

14. The system according to claim 13, wherein adjusting the correction factor includes increasing the correction factor as the estimated ram air difference increases.

15. The system according to claim 13, wherein adjusting the correction factor includes decreasing the correction factor as the estimated ram air difference increases.

Images