Process and engine system

Abstract

Procedure, comprehensive: Monitoring a periodic waveform output of a fuel control system (202) during closed-loop fuel control over several cycles; Estimating an exhaust pressure based on at least one waveform feature, wherein the at least one waveform feature comprises one or more of the frequency, standard deviation, and amplitude of the periodic waveform output, while maintaining a desired stoichiometric air-fuel ratio of an engine (10); and Setting at least one engine operating parameter based on the estimated exhaust pressure.

Description

AREA

[0001] The present description generally relates to a method and an engine system for estimating the exhaust pressure in an internal combustion engine. BACKGROUND / SUMMARY

[0002] Measurements and / or estimates of exhaust pressure from an exhaust stream flowing through an internal combustion engine's exhaust manifold can be used as inputs in various vehicle control strategies to manage engine operation. For example, engines may incorporate a dedicated, standalone pressure sensor positioned upstream of a catalytic converter in the engine's exhaust manifold to measure exhaust pressure. Thus, accurate exhaust pressure measurements can be crucial for controlling the operation of various vehicle control strategies.

[0003] Additionally, excessive exhaust pressure in an engine can lead to increased pump losses and fuel consumption. Exhaust flow restrictions, such as those imposed by particulate filters, can amplify exhaust pressure spikes. For example, a particulate filter restricts the exhaust flow and increases exhaust pressure as it becomes overloaded with soot. Particulate filters can be regenerated periodically to remove accumulated particles. However, these regeneration events can negatively impact fuel consumption. Consequently, accurate exhaust pressure estimates are necessary to determine the particulate filter's load state and schedule regeneration at optimal times to minimize fuel consumption. Furthermore, accurate exhaust pressure estimates are crucial for avoiding and / or minimizing exhaust pressure spikes.

[0004] However, some engines cannot include an exhaust pressure sensor. Dedicated exhaust pressure sensors can increase engine system costs and the complexity of engine control. In these examples, exhaust pressure can be modeled based on alternating engine operating conditions, such as intake air mass flow, and / or on sensor measurements.

[0005] Devices and methods for estimating exhaust pressure are known from the prior art, e.g., from patents JP 2006 - 161 626 A and DE 102016 103 633 A1, in which the exhaust pressure is determined as a function of a relationship between the air-fuel ratio and the output signal of an exhaust gas sensor, whereby the slope of the sensor signal is recognized as pressure-dependent. However, the inventors here have recognized that these exhaust pressure models can have errors that can cascade into additional models that use the modeled exhaust pressure. For example, approaches that aim to measure the exhaust pressure based on the intake air mass flow rate can have reduced accuracy because they do not take into account the effects of exhaust restrictions, such as particulate filters, on the exhaust pressure.Additionally, certain models can be limited by a window in which exhaust pressure can only be modeled under specific engine operating conditions. As a result, engine control may have reduced accuracy based on exhaust pressure estimates during operation outside this window.

[0006] The object of the present invention is therefore to provide an improved method and motor system.

[0007] This problem is solved by the subject matter of the independent claims. Preferred embodiments of the present invention are the subject matter of the dependent claims.

[0008] In one example, the problems described above can be addressed by a method for monitoring periodic waveform outputs from an exhaust air / fuel ratio (AFR) sensor during closed-loop fuel control. This method estimates an exhaust pressure based on one or more cycles of periodic waveform outputs, determined by a standard deviation and mean frequency, and adjusts at least one engine operating parameter based on the estimated exhaust pressure. In this way, an existing engine sensor (e.g., an exhaust AFR sensor) can be used to more accurately estimate the engine exhaust pressure, thereby improving the accuracy of engine control based on exhaust pressure estimates.

[0009] As an example, the AFR sensor can include an exhaust gas lambda sensor and can be designed to measure the partial pressure of oxygen in the exhaust gas. A control unit can adjust the amount of fuel injected into one or more engine cylinders based on the outputs received from the AFR sensor. Thus, fuel injection can be feedback-controlled based on the AFR sensor. However, since the lambda sensor measures the partial pressure of oxygen in the exhaust gas sample, the amount of oxygen measured by the sensor increases with increases in exhaust gas pressure and therefore exhaust gas density. Thus, fluctuations in the AFR sensor output can be used to infer changes in exhaust gas pressure. The AFR sensor output can, in particular, include a periodic waveform signal resulting from a continuous oscillation of substoichiometric and superstoichiometric fuel injection commands.One or more of the frequency, amplitude, and / or standard deviation of the periodic waveform signal from the AFR sensor can fluctuate in relation to changes in exhaust pressure. Thus, changes in the characteristics of the AFR sensor's waveform output can indicate changes in exhaust pressure. A control unit can then adjust engine operation based on these specific changes in exhaust pressure.

[0010] In another description, a method includes monitoring periodic waveform outputs of a fuel control system during closed-loop fuel control, estimating an exhaust pressure based on the waveform outputs of the control system, and setting at least one engine operating parameter based on the estimated exhaust pressure.

[0011] In yet another representation, an engine system comprises an exhaust gas lambda sensor, one or more fuel injectors, and a controller with computer-readable instructions stored in non-volatile memory for: determining a commanded quantity of fuel to be injected by the one or more fuel injectors based on outputs from the exhaust gas lambda sensor, adjusting the one or more fuel injectors to inject the commanded quantity of fuel, and estimating an exhaust pressure based on one or more of the outputs from the exhaust gas lambda sensor and changes in the commanded quantity of fuel over a period of time.

[0012] This allows for more accurate estimates of exhaust pressure, taking into account flow restrictions in the exhaust gas. As a result, engine control can be improved based on these exhaust pressure estimates. Furthermore, the cost of the engine system can be reduced by using an existing engine sensor to estimate exhaust pressure instead of a dedicated pressure sensor.

[0013] It is understood that the foregoing summary is provided to introduce, in a simplified manner, a selection of concepts that are further described in the full description. It is not intended to identify important or decisive features of the claimed subject matter, the scope of which is defined solely in the claims following the full description. Furthermore, the claimed subject matter is not limited to implementations that overcome the disadvantages mentioned above or noted in any part of this disclosure. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 shows a schematic representation of an exemplary engine system comprising a sensor for the air-fuel ratio of the exhaust gas in accordance with an embodiment of the present disclosure. Fig. Figure 2 shows a schematic representation of an exemplary fuel control system for regulating fuel injection into an internal combustion engine based on outputs from an exhaust gas air-fuel ratio sensor, such as the exemplary engine system and air-fuel ratio sensor as in Fig. 1 shown, in accordance with an embodiment of the present invention. Fig. Figure 3 shows a flowchart of an exemplary procedure for estimating exhaust pressure based on outputs from an exhaust air-fuel ratio sensor, such as the exemplary air-fuel ratio sensor as shown in Fig. 1 shown, in accordance with an embodiment of the present invention. Fig. Figure 4A shows a first graph illustrating changes in sensor outputs for the exhaust air-fuel ratio and the commanded fuel injection quantities from a fuel control system under varying exhaust pressures. Fig. Figure 4B shows a second graph illustrating exemplary changes in sensor outputs for the exhaust air-fuel ratio and the commanded fuel injection quantities from a fuel control system under varying exhaust pressures. Fig. Figure 4C shows a third graph illustrating exemplary changes in sensor outputs for the exhaust air-fuel ratio and the commanded fuel injection quantities from a fuel control system under varying exhaust pressures. Fig. 4D shows a fourth graph illustrating exemplary changes in sensor outputs for the exhaust air-fuel ratio and the commanded fuel injection quantities from a fuel control system under varying exhaust pressures. Fig. Figure 5 shows a graph illustrating exemplary settings for various engine actuators under varying exhaust pressures. DETAILED DESCRIPTION

[0014] The following description concerns systems and methods for estimating exhaust pressure in an internal combustion engine, such as the one described in Fig. Figure 1 shows an exemplary engine system. The exhaust pressure can be estimated, in particular, based on outputs from an exhaust air-fuel ratio sensor, such as an exhaust gas lambda sensor. Outputs from the exhaust air-fuel ratio sensor can be used to determine how much fuel to inject into the internal combustion engine (for example, in combination with a desired air-fuel ratio). For example, a fuel control system, such as the one shown in Figure 1, can be used to determine the amount of fuel to be injected into the combustion engine. Fig. 2. The fuel control system shown adjusts the amount of fuel injected into the engine based on the outputs from the exhaust gas air-fuel ratio sensor to maintain a desired air-fuel ratio. Additionally, outputs from the air-fuel ratio sensor can be used to estimate changes in exhaust pressure, as in the example routine from Fig. 3 shown. For example, the Fig. 4A-4D provide exemplary curves illustrating how outputs from the air-fuel ratio sensor can change under varying exhaust pressures over time. In response to changes in exhaust pressure, determined by the air-fuel ratio sensor outputs, an engine control unit, such as the fuel control unit, can adjust one or more engine actuators.

[0015] Now, with reference to Fig. Figure 1 shows a schematic diagram 100 depicting a cylinder of the multi-cylinder engine 10, which may be incorporated into the drive system of an automobile. The engine 10 can be controlled, at least partially, by a control system, including the controller 12, and by input from a driver 132 via an input device 130. In this example, the input device 130 comprises an accelerator pedal and a pedal position sensor 134 for generating a proportional pedal position signal PP. The proportional pedal position signal represents a driver-requested torque, which is a quantity of torque requested by the driver 132. Thus, the driver 132 can request more or less torque by adjusting the position of the input device 130.In one example, the operator can request more torque by pressing input device 130 and request less torque by releasing input device 130.

[0016] The combustion chamber (i.e., the cylinder) 30 of the engine 10 can comprise the combustion chamber walls 32, with the piston 36 positioned therein. The piston 36 can be coupled to the crankshaft 40, so that a reciprocating motion of the piston is translated into a rotational motion of the crankshaft. The crankshaft 40 can be coupled to at least one drive wheel of a vehicle via an intermediate transmission system. Furthermore, a starter motor can be coupled to the crankshaft 40 via a flywheel to enable a starting process of the engine 10.

[0017] The combustion chamber 30 can draw in intake air from the intake manifold 44 via the intake port 42 and discharge combustion gases to the exhaust manifold 48 via the exhaust port 80. The intake manifold 44 and the exhaust manifold 48 can be selectively connected to the combustion chamber 30 via the corresponding intake valve 52 and exhaust valve 54. In some embodiments, the combustion chamber 30 can include two or more intake valves and / or two or more exhaust valves.

[0018] In the example from Fig. 1. The inlet valve 52 and the exhaust valve 54 can be controlled by cam actuation via the cam actuation system 51 and 53, respectively. The cam actuation systems 51 and 53 can each include one or more cams and use one or more of the following systems: cam profile adjustment (CPS), variable cam actuation (VCT), variable valve actuation (VVT), and / or variable valve lift (VVL) systems, which can be operated by the control unit 12 to vary the valve operation. The position of the inlet valve 52 and the exhaust valve 54 can be determined by the position sensors 55 and 57, respectively. In alternative embodiments, the inlet valve 52 and / or the exhaust valve 54 can be controlled by an electric valve actuator.For example, cylinder 30 may alternatively include an inlet valve controlled by an electric valve actuation system and an exhaust valve controlled by cam actuation systems, including CPS and / or VCT systems.

[0019] In some embodiments, each cylinder of the engine 10 can be equipped with one or more injection devices for supplying fuel to it. As a non-limiting example, cylinder 30 is shown to include an injection device 66, which is supplied with fuel from the fuel system 172. The injection device 66 is shown to be directly coupled to cylinder 30 in order to inject fuel directly into it in proportion to the pulse width of a signal FPW received by the controller 12 via the electronic driver 68. In this way, the injection device 66 provides so-called direct injection (hereinafter also referred to as "DI") of fuel into the combustion cylinder 30.

[0020] It is understood that, in an alternative embodiment, the injection device 66 can be an injection device with one nozzle per intake port, which supplies fuel to the intake port upstream of the cylinder 30. It is further understood that the cylinder 30 can receive fuel from a plurality of injection devices, such as a plurality of injection devices with one nozzle per intake port, a plurality of direct injection devices, or a combination thereof.

[0021] Continue at Fig. 1. The intake duct 42 can include a throttle 62 with a throttle plate 64. In this particular example, the position of the throttle plate 64 can be varied by the controller 12 via a signal provided to an electric motor or actuator included in the throttle 62, a design commonly referred to as an electronic throttle control (ETC). For example, the controller 12 can contain a lookup table that relates positions of the input device 130 to specific throttle positions. Thus, based on the position of the input device 130, the controller 12 can command the actuator of the throttle 62 to adjust the throttle plate 64 to the desired position. In this way, the throttle 62 can be operated to vary the amount of intake air supplied to the combustion chamber 30 of the engine's other cylinders.Thus, the throttle plate 64 can be adjusted to regulate the amount of air supplied to the engine 10 based on the position of the input device 130. In particular, the throttle plate 64 can be set to a more open position relative to the amount of actuation of the input device 130. Thus, when the operator 130 actsuates the accelerator pedal of the input device 130, the throttle plate 64 can be set to a more open position to increase the amount of air flowing to the engine cylinder 30. In the description of the throttle plate 64 and any other valves or adjustable openings herein, setting the valve to a more open position includes enlarging an opening formed by the valve, thereby enabling greater fluid mass flow rates through the valve.

[0022] Furthermore, the valves described herein may be one or more binary valves (e.g., two-way valves) or continuously variable valves. Binary valves can be set to either a fully open or a fully closed (blocked) position. A fully open position is a position in which the valve essentially imposes no flow restrictions, and a fully closed position of a valve is a position in which the valve restricts all flow, so that no current can pass through the valve. In contrast, continuously variable valves can be partially opened to varying degrees. Thus, continuously variable valves can be opened to the open and closed positions and additionally to one or more positions between the open and closed positions.Thus, the cross-sectional flow area of ​​continuously adjustable valves can be adjusted to different sizes by setting the valve between the open and closed positions, whereby the opening or cross-sectional flow area formed by the valve increases with increasing deformation towards the open position and away from the closed position.

[0023] It should be noted that in some examples, the controller 12 can adjust the position of the throttle 62 based on both the position of the input device 130 and additional engine operating conditions. For example, the controller 12 can adjust the throttle plate 64 to a more open position in response to increases in auxiliary loads, such as increases in the demand for air conditioning and thus in electrical power supplied to an air conditioning compressor. As another example, the controller 12 can adjust the throttle plate 64 based on the amount of boost provided by a turbocharger or mechanical supercharger of the engine 10. In yet another example, the controller 12 can adjust the throttle plate 64 based on exhaust pressure.For example, the controller 12 can send signals to the actuator of the throttle 62 to adjust the throttle plate 64 to a more closed position in response to exhaust pressures rising above a threshold. The throttle plate 64 can be adjusted to a more closed position than would normally be commanded by the controller 12 during ETC if only the input from the operator 130 via the input device 132 were considered. Closing the throttle 62 can reduce the exhaust pressure.

[0024] Furthermore, the control unit 12 can adjust the amount of fuel injected into cylinder 30 by the injection device 66 based on the position of the throttle valve 64 and the amount of air flowing to the engine cylinder 30, in order to achieve a desired air-fuel ratio. For example, in some cases the desired air-fuel ratio may be stoichiometric (e.g., an air-fuel ratio of 14.7:1).

[0025] The position of the throttle valve 64 can be transmitted to the control unit 12 via the throttle position signal TP, which is provided by a throttle position sensor 65. This sensor can be physically coupled to the throttle plate 62 to measure the position of the throttle plate 64. The intake duct 42 can include an air mass flow sensor 120 to provide a measurement of the amount of air flowing to the cylinder 30. In some examples, the air mass flow sensor 120 can be positioned in the intake duct 42, as in the example from Fig. Figure 1 shows the mass airflow sensor 120. In other examples, however, the mass airflow sensor 120 can be positioned in the intake manifold 44. A manifold air pressure sensor 122 can be positioned in the intake manifold 44 to provide a display of the manifold air pressure (MAP).

[0026] In some examples, engine system 10 may include a turbocharger and / or a mechanical supercharger. In the example from Fig. Figure 1 shows the engine system 10 including a turbocharger. The turbocharger comprises a compressor 90, positioned in the intake duct 42, coupled to a turbine 94, positioned in the exhaust duct 80. Exhaust gases flowing through the exhaust duct 80 can rotate the turbine 94, which may be coupled to the compressor 90 via a shaft 96 or other mechanical connection. As the turbine 94 rotates, it causes the compressor 90 to rotate, and the rotating compressor 90 compresses intake air supplied to the throttle 62. Thus, the compressor 90 can compress the air received from the intake duct 42 to a pressure higher than atmospheric pressure (AT). The amount of pressure added to the intake air can be referred to here as boost pressure.A quantity of charging provided by the compressor 90 can be adjusted via a wastegate valve 168, which is positioned in a bypass channel 166 of the turbine 94.

[0027] The bypass channel 166 can be coupled at opposite ends to the exhaust channel 80 and around the turbine 94, thus providing a route for exhaust gases to flow around the turbine 94. The wastegate valve 168 can be positioned in the bypass channel 166 to regulate the amount of gas flowing through the bypass channel 166 and thus through the turbine 94. The wastegate valve 168 can be set to a more open position to increase the amount of gas flowing through the bypass channel 166 and decrease the amount of gas flowing through the turbine 94. Conversely, the wastegate valve 168 can be set to a more closed or more open position to increase the amount of gas flowing through the turbine 94 and to decrease the amount of gas flowing through the bypass channel 166.Thus, opening the wastegate valve 168 can reduce the rotational speed of the turbine 94 and therefore reduce the amount of boost provided by the compressor 90. Conversely, closing the wastegate valve 168 can increase the rotational speed of the turbine 94 and increase the amount of boost provided by the compressor 90. The controller 12 can be electrically coupled to an actuator of the wastegate valve 168. This allows the actuator to adjust the position of the wastegate valve 168 based on signals received from the controller 12.

[0028] In one example, the controller 12 can adjust the wastegate valve 168 to a more open position to reduce the exhaust pressure in the exhaust channel 80. Specifically, in response to the exhaust pressure exceeding a threshold, the controller 12 can adjust the wastegate valve 168 to a more open position to reduce the exhaust pressure.

[0029] The ignition system 88 can provide a spark to the combustion chamber 30 via the spark plug 92 in response to a pre-ignition signal SA from the control unit 12 under selected operating modes. Although spark ignition components are shown, the combustion chamber 30 or one or more other combustion chambers of the engine 10 can be operated in a compression ignition mode with or without a spark plug. In yet other examples, the engine 10 can be configured as a diesel engine and may not include a spark plug 92.

[0030] An upstream first sensor 126 for the air-fuel ratio (AFR) is shown coupled to the exhaust duct 80 upstream of the emission control device 70. The upstream first AFR sensor 126 can be any suitable sensor for providing an indication of the exhaust gas air-fuel ratio, such as a lambda sensor. For example, the AFR sensor 126 can be a lambda sensor such as a linear wideband lambda sensor or a UEGO (Universal or Wide-Range Exhaust Gas Oxygen). Thus, the upstream first AFR sensor 126 can also be referred to herein as the upstream first lambda sensor 126. In other examples, the AFR sensor 126 can be one or more of a dual-state narrowband lambda sensor or an EGO, a HEGO (heated EGO), a NOx, HC, or CO sensor.In embodiments where the AFR sensor 126 is a lambda sensor, such as a UEGO sensor, the AFR sensor 126 is designed to provide an output, such as a voltage signal, that is proportional to the amount of oxygen contained in the exhaust gas. The controller 12 uses the output to determine the air-fuel ratio of the exhaust gas.

[0031] In particular, the partial pressure of oxygen in the exhaust gas, detected by the AFR sensor 126, can be inversely proportional to the voltage generated by the sensor 126 and transmitted to the controller 12. This means that the voltage output by the sensor 126 can decrease monotonically as the amount of oxygen in the exhaust gas increases. Thus, the voltage output by the sensor 126 can be higher for air-fuel ratios richer than stoichiometry (e.g., an air-fuel ratio of 14.7:1) and lower for air-fuel ratios leaner than stoichiometry.

[0032] An emission control device 70 is shown downstream of the AFR sensor 126 along the exhaust duct 80. The device 70 can be a three-way catalytic converter (TWC) designed to reduce NOx and oxidize CO and unburned hydrocarbons. In some embodiments, the device 70 can be a NOx trap, various other emission control devices, or combinations thereof.

[0033] A particulate filter 82 can be located downstream of and / or within the emission control device 70. The particulate filter 82 can trap particles such as soot. The particulate filter 82 can be one or more diesel particulate filters (DPF) and / or gasoline particulate filters (GPF). As soot accumulates on the filter 82, the exhaust pressure can increase. Therefore, the filter 82 can include a heater 84 for periodically regenerating the filter 82. The heater 84 can be electrically coupled to the controller 12 and can be switched on based on signals received from the controller 12. For example, in response to the exhaust pressure exceeding a threshold, the controller 12 can send signals to the heater 84 to switch it on and burn off the particles trapped within the filter 82.Thus, the heater 84 can be switched on to burn off particles that have accumulated on the filter 82, thereby regenerating the filter 82. In some examples, the filter 82 can be regenerated at regular intervals, such as after a threshold value for duration, number of engine cycles, etc., and / or based on engine operating conditions such as exhaust pressure.

[0034] A second, downstream AFR sensor 128 is shown coupled to the exhaust gas duct 80 downstream of the emission control device 70. The downstream sensor 128 can be any suitable sensor for providing an indication of the air-fuel ratio of the exhaust gas, such as a UEGO, EGO, HEGO, etc. In one embodiment, the downstream sensor 128 is an EGO designed to indicate the relative enrichment or leaning of the exhaust gas after it has passed through the emission control device 70. Thus, the EGO can provide an output in the form of a switching point or the voltage signal at the point at which the exhaust gas changes from lean to rich.

[0035] Furthermore, in the disclosed embodiments, an exhaust gas recirculation (EGR) system can direct a desired portion of the exhaust gas from the exhaust duct 80 into the intake duct 42 and / or intake manifold 44 via the EGR channel 140. The amount of EGR provided to the intake duct 42 can be varied by the control unit 12 via the EGR valve 142. Additionally, the EGR sensor 144 can be located within the EGR channel and provide a reading of one or more values, including exhaust gas pressure, temperature, and concentration. Under certain conditions, the EGR system can also be used to regulate the temperature of the air-fuel mixture in the combustion chamber.

[0036] Control 12 is in Fig. 1 is represented as a microcomputer, comprising a microprocessor unit 102, input / output ports 104, an electronic storage medium for executable programs and calibration values, represented in this specific example as a read-only memory chip 106, random access memory 108, keep-alive memory 110, and a data bus. In addition to the signals described above, the controller 12 can receive various signals from sensors coupled to the motor 10, including the measurement of mass airflow (MAF) from a mass airflow sensor 120; engine coolant temperature (ECT) from a temperature sensor 112 coupled to a cooling sleeve 114; a profile ignition pulse (PIP) signal from a Hall-effect sensor 118 (or other type) coupled to a crankshaft 40; and a throttle position (TP) from a throttle position sensor. and an intake manifold absolute pressure (MAP) signal from sensor 122.The motor speed signal RPM can be generated from the PIP signal by the controller 12.

[0037] A read-only storage medium 106 can contain computer-readable data that represents non-volatile instructions executable by the processor 102 to perform the procedures described below, as well as other variants that are assumed and not explicitly listed. The controller 12 receives signals from the various sensors. Fig. 1 and suspends the various actuators Fig. 1 to adjust the engine operation based on the received signals and instructions stored in a memory of the control unit 12. Thus, the control unit can estimate the exhaust pressure in the exhaust channel 80 based on signals received from one or more of the AFR sensors 126 and / or 128. Based on the exhaust pressure and / or other engine operating parameters such as driver demand torque, boost pressure, engine speed, etc., the control unit 12 can adjust one or more of the wastegate valve 168, the intake throttle 62, and the heater 84 of the particulate filter 82.

[0038] As described above, shows Fig. 1 only one cylinder of a multi-cylinder engine and each cylinder can equally include its own set of inlet / outlet valves, fuel injection device, spark plugs, etc.

[0039] Continue with Fig. Figure 2 shows a schematic representation with a detailed illustration of an engine control system that can be used to control the engine's air-fuel ratio. In particular, it shows Fig. 2 a schematic representation of a fuel control system 200 comprising a control 202 which is the same as or similar to the control 12 referred to above Fig. 1, which sends electrical signals to one or more fuel injection devices 266 for adjusting the amount of fuel injected into one or more cylinders of an engine 210. The injection devices 266 may be the same as or similar to the fuel injection device 66 described above with reference to Fig. 1 is described, and the engine 210 may be the same as or similar to the engine 10 described above with reference to Fig. 1 is described, his.

[0040] The control unit 200 can adjust the amount of fuel injected by the injectors 266 based on a desired air-fuel ratio, such as stoichiometry (14.7:1), and on outputs received from an exhaust gas AFR 250. The AFR sensor 250 may also be referred to herein as the exhaust gas lambda sensor 250. The AFR sensor 250 may be the same as, or similar to, the AFR sensor 126 described above with reference to Fig. As described in section 1, the AFR sensor 250 can be one or more of a HEGO, EGO, UEGO, or other type of lambda sensor that measures a quantity (e.g., mass, moles, etc.) of oxygen in exhaust gases in the exhaust duct 251. Therefore, outputs from the AFR sensor 250 can correspond to the quantity of oxygen contained in the exhaust gases. The AFR sensor 250 can send an output voltage signal 208, corresponding to the quantity of oxygen in the exhaust gases, to the controller 202. Thus, the AFR sensor 250 can be electrically coupled to the controller 200.

[0041] Therefore, the outputs of the AFR sensor 250 can change depending on the oxygen concentration in the exhaust gases and / or the exhaust gas density. Specifically, the amount of oxygen measured by the AFR sensor 250 can increase with increases in the oxygen concentration in the exhaust gases and / or increases in the exhaust gas density. Thus, even if the oxygen concentration in the exhaust gases remains essentially the same and not zero, an increase in exhaust gas density can cause a corresponding increase in the amount of oxygen measured by the AFR sensor 250. This is due to the fact that when the exhaust gases increase in density, the absolute amount (e.g., mass) of the gases, including oxygen, per unit volume of the measured exhaust gases also increases.

[0042] In particular, a voltage output signal 208 generated by the AFR sensor 250 can increase for decreases in the amount of oxygen contained in the exhaust gases. Likewise, the voltage output by the AFR sensor 250 can decrease for increases in the amount of oxygen contained in the exhaust gases, as described in more detail below with reference to the Fig. 4A-4D described. The amount of oxygen contained in the exhaust gases can increase with increasing exhaust gas pressure. This means that the voltage output from the AFR sensor 250 can decrease with increasing exhaust gas pressure at a given air-fuel ratio and / or oxygen concentration, as described in more detail below with reference to the Fig. 4A-4D described.

[0043] However, it should be understood that the amount of oxygen measured by the AFR sensor cannot change in response to changes in exhaust gas density if there is essentially no (e.g., zero) oxygen in the exhaust gases. That is, if the exhaust gases contain no oxygen, changes in exhaust gas density cannot affect the amount of oxygen measured by the AFR sensor 250, because the amount of oxygen remains the same (zero) when the exhaust gases contain no oxygen.

[0044] A catalyst 270, which is the same as or similar to the emission control device 70 described above with reference to Fig. 1 is described, can be, is used to clean exhaust gases before they are emitted into the atmosphere, as detailed above with reference to Fig. As described in section 1. Additional sensors, generally located at 201, provide further information about engine operation to the control unit 202, such as crankshaft position, crankshaft angular velocity, throttle position, etc. The information from these sensors is used by the control unit 202 to control engine operation.

[0045] An air mass flow detector 215, positioned at the air intake of the engine 210, detects the amount of air supplied to the cylinders for combustion. The controller 202 is shown in electrical communication with the AFR sensor 250 and injection devices 266 for adjusting the fuel injection quantities based on outputs from the AFR sensor 250. The controller 202 can include one or more microcontrollers, each comprising one or more integrated circuits that include a processor, a read-only memory (ROM) that stores configuration data and the programs executed by the processor, peripheral data processing circuitry, and random-accessible read / write memory for storing dynamically changing data.These microcontrollers typically include integrated analog / digital converter capabilities, which are useful for converting analog signals from sensors and the like into digitally expressed values, as well as timing controls / counting devices for generating timed interruptions.

[0046] A microcontroller 207 can further be included in the controller 202 to implement proportional and integral (PI) closed-loop feedback control for fuel injection in order to maintain the air-fuel ratio at a desired air-fuel ratio, such as stoichiometry. The microcontroller 207 can include a proportional element 121, an integral element 122, and an adder 120 to sum the outputs of the proportional and integral elements.

[0047] The AFR sensor 250 generates voltage outputs that can be communicated to the comparator 224. The voltage outputs of the AFR sensor 250 can be raw, unfiltered outputs from the sensor 250. In some examples, an AFR sensor module 253 can be included in the fuel control system 200 and coupled to the AFR sensor 250 to modify the sensor 250's outputs. In particular, the AFR sensor module 253 can contain instructions stored in non-volatile memory to adjust the outputs from the AFR sensor 250 to compensate for changes in exhaust pressure. As explained above, changes in exhaust pressure can affect the output of the AFR sensor 250 even if the oxygen concentration in the exhaust gas remains constant. The AFR sensor module 253 can adjust the signal communicated to the comparator 224 to compensate for these pressure changes in the exhaust gas.As an example, the AFR sensor module 253 can adjust the voltage output by the AFR sensor to a higher voltage in response to an increase in exhaust pressure, which indicates a lower amount of oxygen.

[0048] In other examples, however, the AFR sensor module 253 may not be included in the fuel control system 200, and the raw voltage outputs of the AFR sensor 250 may be communicated directly to the comparator without modification or adjustment. The signal provided to the comparator 224 by the AFR sensor 250 may be referred to as the LAMBDA signal 208. In examples where the AFR sensor module 253 is included in the fuel control system 200, the LAMBDA signal may be generated by the module 253 and may include the set AFR sensor output, which has been pressure compensated. However, in examples where the AFR sensor module 253 is not included in the fuel control system 200, the LAMBDA signal may be the raw voltage output of the AFR sensor and may not be pressure compensated.

[0049] The comparator 124 receives the lambda signal 208 and generates a deviation signal 231, which represents the deviation or difference between the air-fuel ratio measured via the lambda signal and the desired air-fuel ratio. The controller 202 can modify the signal 231 at an adder 223 based on the air-fuel distortion signal 245, which is generated by an air-fuel distortion signal generation function 226. Based on the deviation, the microcontroller 207 then generates proportional and integral factors at the proportional element 221 and the integral element 222, respectively. Together, the proportional and integral elements are used to generate a commanded fuel injection signal 216, referred to as LAMBSE. In some examples, LAMBSE is the commanded quantity of fuel to be injected by the injection devices.Thus, LAMBSE can be communicated directly to the fuel injections 266. In other examples, however, LAMBSE is a change in the fuel injection quantity from an actual fuel injection quantity. In such examples, such as the one in . Fig. As shown in Figure 2, LAMBSE 216 can be communicated to a summing module 228, which can adjust LAMBSE 216 based on a lambda sensor monitoring function 225. The modified LAMBSE signal can be communicated to another control module 229, which calculates a fuel supply value and provides the resulting fuel supply value signal 217 to the injection devices 266. Exemplary waveforms of the LAMBSE signal 216 and the LAMBDA signal 208 are shown below with reference to the Fig. 4A-4D shown.

[0050] In some examples, the controller 202 can also implement an air-fuel modulator function, shown at 227, a lambda sensor monitoring function, shown at 225, and an (L / K) distortion generation function, shown at 226.

[0051] In examples where the AFR sensor module 253 is included in the fuel control system 202, the LAMBDA signal 208 can be essentially unaffected by varying exhaust pressures. Thus, the LAMBSE signal, generated based on the LAMBDA signal, can remain essentially the same at constant oxygen concentrations under varying exhaust pressures. However, the controller 202 can still receive a direct raw output from the AFR sensor 250, even with the module 253 included. Therefore, the controller 202 can receive periodic waveform outputs from the sensor 250 that have not been set or modified by the module 253. Thus, the controller 202 can receive outputs directly from the sensor 250, even with the module 253 included. These outputs cannot be compensated for changes in exhaust pressure.Thus, fluctuations in these raw sensor outputs can be used by the controller 202 to estimate the exhaust pressure, even when the module 253 is included. The AFR sensor 250 can therefore be directly electrically coupled to the controller 202, even when the AFR sensor module 253 is included. The AFR sensor 250 can thus be directly electrically coupled to both the controller 202 and the module 253. The module, in turn, can also be directly electrically coupled to the controller 202. The controller 202 can, however, use the input received directly from the AFR sensor 250 to estimate the exhaust pressure and can use the set AFR sensor output received from the AFR sensor module 253 to determine the amount of fuel to be injected by the injection devices 266.

[0052] In other examples where module 253 is not included, the LAMBDA signal can vary under essentially constant oxygen concentrations when the exhaust pressure changes. Thus, the LAMBSE signal will change accordingly due to the changes in exhaust pressure. This is explained in more detail below with reference to the Fig. As explained in 3-5, the controller 202 can estimate the exhaust pressure based on the raw voltage output from the AFR sensor 250. However, in examples where the module 253 is not included, the controller 202 can additionally or alternatively estimate the exhaust pressure based on the LAMBSE signal 216.

[0053] Now, with reference to Fig. Figure 3 shows an exemplary method 300 for estimating the exhaust pressure based on outputs from an exhaust AFR sensor (e.g., the AFR sensor 126 described above in Fig. 1 is described). The instructions for carrying out procedure 300 can be issued by a controller (e.g., the controller 12 described above in Fig. 1 is described) are executed based on instructions stored in a memory of the controller and in conjunction with signals received from sensors of the motor system, such as those mentioned above in relation to Fig. 1. Sensors described. The controller can use motor actuators of the motor system to adjust motor operation according to the procedures described below.

[0054] Procedure 300 begins at 302, which involves measuring and / or estimating the engine operating conditions. The engine operating conditions may include one or more of a fuel injection quantity, a desired air-fuel ratio, a boost pressure, a position of an intake throttle (e.g., the throttle 62 described above in Fig. 1), an exhaust pressure, a load on a particulate filter (e.g. the particulate filter 82 described above in Fig. 1 is described), including an engine speed, etc.

[0055] After estimating and / or measuring the engine operating conditions, procedure 300 can be continued from 302 to 304, which includes determining whether steady-state engine conditions exist. Steady-state engine conditions may include conditions in which the engine speed and / or driver-demand torque remain substantially constant for a threshold duration. Thus, procedure 300 at 304 may include determining whether one or more of the driver-demand torque and / or engine speed remain within a threshold range for a threshold duration. The driver-demand torque may be determined based on the position of an accelerator pedal (e.g., the input device 132 described above). Fig. 1 is described), as well as by a pedal position sensor (e.g. the pedal position sensor 134, which is described above in Fig. The motor speed can be estimated by a motor speed sensor, such as a Hall-effect sensor 118, which is described above in 1. Fig. 1 is provided. If the engine speed and / or driver-demand torque fluctuate outside the threshold range, then it can be determined that steady-state conditions are not present. If steady-state engine conditions are not present, procedure 300 continues from 304 to 306, which includes a non-estimation of exhaust pressure based on LAMBSE or LAMBDA signals. As above with reference to Fig. As described in section 2, the LAMBSE signal represents a commanded fuel injection quantity, and the raw LAMBDA signal represents the voltage output from the AFR sensor, which is not compensated for pressure. Procedure 300 then returns.

[0056] Upon returning to 304, if steady-state engine conditions are determined, procedure 300 can continue from 304 to 305, which includes determining whether closed-loop fuel control is in operation. That is, at 305, procedure 300 can include determining whether the fuel control is feedback-driven by the controller based on outputs from the AFR sensor. The controller can switch between closed-loop and open-loop fuel control under varying engine operating conditions. For example, during a fuel cut-off for deceleration, the controller can switch to open-loop fuel control.During open-loop fuel control, the controller cannot adjust the fuel injection quantity based on outputs from the AFR sensor and can inject a desired amount of fuel based on the air mass flow rate and a lookup table that relates air mass flow rates to desired fuel injection quantities.

[0057] If it is determined that closed-loop fuel control is not present and that the fuel control system is operating with open-loop control, then procedure 300 from 305 to 307 can be continued, which involves estimating the exhaust pressure based on changes in the raw lambda signal. During steady-state engine operating conditions, when the mass airflow and driver-demand torque are substantially equal, the commanded fuel injection quantity can remain substantially constant during open-loop control. Thus, fluctuations in the raw lambda output from the AFR sensor can be the result of fluctuating exhaust pressures. Therefore, the exhaust pressure can be derived based on changes in the raw AFR sensor output during open-loop fuel control when the mass airflow rate in the engine intake is substantially constant.The exhaust pressure can be set to increase with increases in the amount of oxygen indicated in the raw lambda output from the AFR sensor, and to decrease with decreases in the amount of oxygen indicated in the raw lambda output from the AFR sensor. Thus, the exhaust pressure can increase for decreases in the voltage output from the AFR sensor and vice versa.

[0058] In other examples, however, procedure 300 at 307 may include not estimating the exhaust pressure and freezing exhaust pressure estimates. Thus, in some examples, the exhaust pressure can only be estimated during closed-loop air-fuel ratio control and cannot be updated or estimated during open-loop control. This means that the value of the most recent exhaust pressure estimate prior to entering open-loop air-fuel ratio control can be used as the exhaust pressure estimate for the duration of the open-loop air-fuel ratio control period. Procedure 300 then returns.

[0059] If it is determined that the fuel control system is in closed-loop fuel control mode, then procedure 300 can be continued from 305 to 308, which involves monitoring the raw LAMBDA signal and / or LAMBSE signal over a period of time. As described above, the raw LAMBDA signal corresponds to the voltage output by the AFR sensor, which represents the amount of oxygen in the exhaust gas. The raw LAMBDA signal is not pressure-compensated and therefore cannot be adjusted by an AFR sensor module that adjusts the raw LAMBDA signal based on the exhaust pressure, such as the AFR sensor module 253 described above. Fig. 2 is described, changed or created.

[0060] In some examples, the period at 308 can be any amount of time (e.g., a time interval). In another example, the period can be a number of cycles of the LAMBDA and / or LAMBSE signals. As in the Fig. As shown in Figures 4A-4D, the LAMBDA and LAMBSE signals can be periodic waveform signals. The frequency and amplitude of the LAMBDA and / or LAMBSE signals can change when the exhaust pressure fluctuates. However, the LAMBDA and LAMBSE signals can maintain a periodic waveform during closed-loop fuel control because the commanded fuel injection quantity oscillates back and forth between richer and leaner values ​​of the desired air-fuel ratio (e.g., stoichiometry). In some examples, the period can be exactly one cycle (e.g., one time interval) of the LAMBDA and / or LAMBSE signals. In another example, the period can be at least one cycle of the LAMBDA and / or LAMBSE signals. In yet another example, the period can be one switching cycle, which is half the duration of the LAMBDA and / or LAMBSE signals. In other examples, the period can be more than two LAMBDA and / or LAMBSE cycles.In yet other examples, the period can be a number of engine cycles, a number of cylinder cycles, and so on. For instance, the period can encompass a cycle of one engine cylinder. In another example, the period can encompass the cycles of two or more engine cylinders. In still other examples, the period can encompass an entire engine cycle, where all engine cylinders complete a cycle. In yet other examples, the period can encompass more than one engine cycle.

[0061] After monitoring the raw LAMBDA and / or LAMBSE signals over the period, procedure 300 continues from 308 to 310, which involves determining the changes in the LAMBSE signal at a switching point. This is described in more detail below with reference to the Fig. As described in 4A-4D, the switching point of the LAMBSE signal can encompass the time at which the LAMBDA signal switches from below the setpoint to above the setpoint, thus resulting in the LAMBSE signal switching from superstoichiometric to substoichiometric and vice versa. A setpoint for the LAMBDA signal can be assigned by the controller. The LAMBDA signal can be compared to this setpoint to determine the LAMBSE signal. In particular, the deviation between the actual LAMBDA signal and the setpoint can be used to generate proportional and integral factors that are used in the feedback control loop to generate the LAMBSE signal, as described above with reference to Fig. 2 described.

[0062] If the LAMBDA signal is leaner than the setpoint, the LAMBSE signal can command an increase in fuel injection to enrich the air-fuel ratio (e.g., decrease the air-fuel ratio). Conversely, if the LAMBDA signal is richer than the setpoint, the LAMBSE signal can command a decrease in fuel injection to lean the air-fuel ratio (e.g., increase the air-fuel ratio). In some examples, the setpoint may represent an approximately stoichiometric air-fuel ratio. However, in other examples, the setpoint may be adjusted to make the engine run leaner or richer than stoichiometric.

[0063] The change in LAMBSE at the switching point can include the amount by which the LAMBSE signal changes at the switching point, or, within the switching threshold time, the LAMBDA signal changes either from richer to leaner than the setpoint or from leaner to richer than the setpoint. In some examples, Procedure 300 at 310 can include determining the change in the LAMBSE signal at only one switching point during the period in which the LAMBSE signal was monitored. In another example, Procedure 300 at 312 can include calculating the change in the LAMBSE signal at two or more of the switching points included in the period over which the LAMBSE signal at 308 was monitored. In yet another example, the procedure 300 at 310 can include calculating the change in the LAMBSE signal at each of the switching points contained in the period over which the LAMBSE signal at 308 was monitored.In yet another example, the procedure 300 at 310 may include calculating the mean change of the LAMBSE signals at two or more of the switching points contained in the period over which the LAMBSE signal at 308 was monitored.

[0064] Procedure 300 can then proceed from 310 to 312, which includes determining the amplitude of the LAMBDA and / or LAMBSE signals. In some examples, procedure 300 may include determining the amplitude of the LAMBDA and / or LAMBSE signals for only one cycle of the one or more signals. In other examples, procedure 300 may include calculating the amplitude for each cycle of two or more cycles of the LAMBDA and / or LAMBSE signals contained in the period. In still other examples, procedure 300 may include averaging the amplitudes of the LAMBDA and / or LAMBSE signals over the period or for segments of the period. In yet another example, procedure 300 at 312 may include determining the magnitude of the difference between a maximum and a minimum of a cycle of the LAMBDA and / or LAMBSE signals.Further examples include averaging the magnitude of the difference between maxima and minima of two or more cycles of the LAMBDA and / or LAMBSE signals during the period. Procedure 300, as described in 312, may additionally or alternatively include calculating the standard deviation of the LAMBSE and LAMBDA signals. The standard deviation may be calculated over one or more of the entire period, a portion of the period, a single cycle, multiple cycles, or a portion of a cycle of the signals.

[0065] Procedure 300 can then proceed to 314, which involves determining the frequency and / or a time interval of the LAMBDA and / or LAMBSE signals. The time interval can be the amount of time for the LAMBDA and / or LAMBSE signal to complete a cycle. In some examples, however, procedure 300 at 314 can involve determining the frequency and / or time interval of the LAMBDA and / or LAMBSE switching cycles. As described above in 312 and 310, the frequency and / or time intervals of the LAMBDA and / or LAMBSE signals can be calculated for each cycle, segments of the cycle, multiple cycles, and / or averaged over multiple cycles, etc.

[0066] Procedure 300 can then proceed from 314 to 315, which involves filtering the LAMBDA and / or LAMBSE signals based on one or more of atmospheric pressure and altitude.

[0067] Procedure 300 can then proceed from 315 to 316, which involves determining the exhaust pressure based on changes in the LAMBDA and / or LAMBSE signals, rather than based on measurements from an exhaust pressure sensor. Thus, in some examples, the exhaust pressure can be estimated solely based on outputs from the AFR sensor. In some examples, the controller may include a lookup table that relates one or more of the frequency, duration, amplitude, etc., of the LAMBDA and / or LAMBSE signals to exhaust pressures. Thus, based on one or more of the amplitude, frequency, duration, etc., of the LAMBDA and / or LAMBSE signals, the controller can determine the exhaust pressure using the lookup table. In another example, the controller can determine the exhaust pressure based on changes in one or more of the frequency, duration, and amplitude of the LAMBDA and / or LAMBSE signals over time.For example, the exhaust pressure can increase for one or more of the following: increases in the amplitude of the LAMBDA and / or LAMBSE signals, increases in frequency, and thus decreases in the duration of the LAMBDA and / or LAMBSE signals. Therefore, the control system can search for trends in the LAMBDA and / or LAMBSE signals over time and use the relative changes in the signals to determine fluctuations in exhaust pressure.

[0068] Procedure 300 can then proceed from 316 to 318, which involves adjusting at least one engine operating parameter based on the estimated exhaust pressure. For example, at 318, procedure 300 can involve adjusting one or more of an intake throttle (e.g., the intake throttle 62 described above in Fig. 1), a wastegate valve (e.g., the wastegate valve 168 described above in Fig. 1) and a particle filter heater (e.g., the heater 84 described above in Fig. (as described in section 1). For example, the controller can adjust the wastegate valve to a more open position in response to increases in exhaust pressure. In another example, the controller can adjust the intake throttle to a more closed position in response to increases in exhaust pressure. In yet another example, the controller can initiate particulate filter regeneration and activate the heater when the exhaust pressure exceeds a threshold and the particulate filter load is greater than a threshold. Closing the intake throttle, opening the wastegate valve, and regenerating the particulate filter can reduce exhaust pressure. For example, the controller can adjust the positions of the wastegate and / or the intake throttle by setting a pulse-width modulated signal that is sent from the controller to corresponding actuators of the valves.The controller can switch on the particulate filter heater via a pulse-width modulated signal, which is sent to a power source of the heater to increase the amount of current supplied to it. Procedure 300 then returns.

[0069] Regarding the Fig. Figures 4A-4D show these four example graphs displaying raw outputs from an exhaust gas AFR sensor (e.g., the AFR sensor 126 described above in Fig. (as described in 1) under varying exhaust pressures during closed-loop fuel control. Thus, the graphs in the Fig. Figures 4A-4D show different examples of how exhaust pressure can influence the outputs of the AFR sensor during closed-loop fuel control, where a commanded quantity of fuel to be injected into one or more engine cylinders is set based on the AFR sensor output. Furthermore, the graphs in the Fig. 4A-4D Changes in a commanded fuel injection quantity (LAMBSE) during closed-loop fuel operation. The LAMBSE signal can thus be generated based on the outputs from the AFR sensor to achieve a desired air-fuel ratio. Exemplary changes in exhaust pressure are shown in curves 402, 412, 432, and 452 in graphs 400, 425, 450, and 475, respectively. Furthermore, exemplary changes in the AFR sensor output are shown in curves 404, 414, 434, and 454 in graphs 400, 425, 450, and 475, respectively. Exemplary changes in the LAMBSE signal are shown in the curves 406, 416, 436 and 456 in graphs 400, 425, 450 and 475 respectively.

[0070] The exhaust pressure AFR sensor output and the LAMBSE signal output in the Fig. Figures 4A-4D are shown along a horizontal time axis. Along the vertical axis, the voltage of the AFR sensor output can decrease with increasing oxygen levels. The LAMBSE signal can become richer with increasing fuel injection volume.

[0071] The AFR sensor setpoint, which is the point against which the AFR sensor output is compared to generate the LAMBSE signal, is represented as dotted line 405 in graphs 400, 425, 450, and 475. In examples where the desired air-fuel ratio is set to stoichiometric, the setpoint can represent an approximately stoichiometric mixture. Thus, the setpoint can represent a predicted AFR sensor output that would be expected if the actual air-fuel ratio matched the desired air-fuel ratio. If the AFR sensor output matches the setpoint, the desired air-fuel ratio can be achieved. If the AFR sensor registers more oxygen than would be present at the desired air-fuel ratio (above dotted line 405), the exhaust mixture may be leaner than desired.Conversely, if the AFR sensor registers less oxygen than would be present at the desired air-fuel ratio (below the dotted line 405), the exhaust mixture may be richer than desired.

[0072] Furthermore, the amount of fuel that would be commanded to achieve the desired air-fuel ratio is represented as dotted line 407 in graphs 400, 425, 450, and 475. If the AFR sensor detects a mixture that is leaner than desired, the LAMBSE signal can command a fuel injection quantity that is richer than desired to bring the air-fuel ratio closer to the desired ratio. Thus, the LAMBSE signal can be richer than stoichiometric (above dotted line 407) if the AFR sensor detects a mixture that is leaner than desired. If the air-fuel ratio is richer than desired, the LAMBSE signal can command less fuel to be injected to bring the air-fuel ratio closer to the desired ratio.Thus, the LAMBSE signal can be leaner than stoichiometric (below the dotted line 407) if the AFR sensor registers a mixture richer than desired. This is shown in the graphs in the [reference]. Fig. As shown in 4A-4D, the LAMBDA and LAMBSE signals can move cyclically back and forth between leanness and enrichment in a periodic waveform.

[0073] As in the Fig. As shown in Figures 4A-4D, the AFR sensor output and the LAMBSE signals can exhibit periodic waveforms during closed-loop fuel control. Each cycle of the AFR sensor output signal includes a peak (a maximum value representing maximum enrichment) and a trough (a minimum value of the signal representing maximum leanness). The peaks and troughs for different AFR sensor cycles can vary depending on the exhaust pressure. The duration of an example single cycle is represented by λ. S represented. Thus, λ denotes S the time interval or wavelength of the AFR sensor output signal. Furthermore, the amplitude of the signal is determined by A. sThe amplitude can be defined as half the difference or half the distance between successive vertices and troughs. The deviation can be defined as the total difference or total distance between successive vertices and troughs, or twice the amplitude.

[0074] Similarly, each LAMBSE signal cycle can include a minimum (a minimum value) and a maximum (a maximum value). The minima and maxima for different AFR sensor cycles can change depending on the exhaust pressure. The duration of an exemplary single LAMBSE signal cycle is denoted by λ. L2 represented. Thus, λ denotes L2the time interval or wavelength of the LAMBSE signal. As defined above, the LAMBSE signal changes from superstoichiometric to substoichiometric, or vice versa, when the AFR sensor output crosses the setpoint. Specifically, when the AFR sensor output changes from leaner than setpoint to richer than setpoint, the LAMBSE signal switches from superstoichiometric to substoichiometric. Conversely, the LAMBSE signal switches from substoichiometric to superstoichiometric when the AFR sensor output changes from richer than setpoint to leaner exhaust gas than setpoint. Fig. Figure 4A shows two exemplary, consecutive switching points. The time interval between two consecutive switching points can be interpreted here as the switching time interval λ. L1The switching frequency can be defined. Thus, the switching frequency can be used to define the rate at which the Lambse signal switches between substoichiometric and superstoichiometric. In other words, the switching frequency can be used to define the number of switching points that occur within a unit of time, with increases in the switching frequency corresponding to increases in the number of switching points that occur within a unit of time.

[0075] Furthermore, the Lambse signal at the switching point can exceed the stoichiometry by a preset amount. The amount by which the Lambse signal exceeds the stoichiometry can be referred to as the fuel offset. Thus, the fuel offset can be the difference between the stoichiometry and the Lambse signal at the end of the switching point, as in Fig. 4A is marked. A first amplitude of the LAMBSE signal is given by A L1The first amplitude can be the difference or distance between a maximum and / or a minimum and a dotted line 407 (e.g., stoichiometry). A second amplitude of the Lambse signal is represented by A L2 The second amplitude of the Lambse signal can be the difference or distance between a maximum or minimum and the subsequent fuel offset at the switching point. Thus, at a switching point, the Lambse signal can transition either from a minimum (maximum lean value) to a superstoichiometric value by an amount defined by the fuel offset, or from a maximum (maximum rich value) to a substoichiometric value by an amount defined by the fuel offset. Furthermore, the variation in one cycle of the Lambse signal can be defined as the total difference or distance between successive minima and maxima.

[0076] Furthermore, the standard deviation of the LAMBSE and AFR sensor output signals can be defined as the amount of signal deviation. Thus, as the standard deviation of the signals increases, the amplitude or deviation of the signal cycles can also increase. This means that the distribution between minimum and maximum values ​​for each signal cycle can increase with increasing standard deviation. In this way, the standard deviation of several LAMBSE and / or AFR sensor output cycles can be used to determine the mean signal distribution across the sample cycles. Additionally, one or more of the standard deviation, amplitude, frequency, time interval, wavelength, etc., from a single or multiple AFR sensor output cycle can be compared with other single or multiple AFR sensor output cycles to determine changes in exhaust pressure.Similarly, one or more of the standard deviation, amplitude, frequency, time span, wavelength, etc. of a single cycle or multiple cycles of the LAMBSE signal can be compared with other single or multiple cycles of the LAMBSE signal to determine changes in exhaust pressure.

[0077] For example, if first Fig. Figure 4A shows a first embodiment of how the AFR sensor outputs and / or the LAMBSE signal can be affected under varying exhaust pressures. In particular, it shows Fig. 4A, how the standard deviation or amplitude of the AFR sensor output and / or the LAMBSE signals can be affected under varying exhaust pressures. The standard deviation and / or amplitude of the AFR sensor output increases with increasing exhaust pressure. That is, the peaks and / or troughs can increase in distance from the setpoint 405 as the exhaust pressure increases. Thus, the exhaust pressure can be derived based on the standard deviation and / or amplitude of the AFR sensor output. For example, a controller (e.g., the controller 12 described above in Fig. (as described in section 1) monitor the AFR sensor output before t1 until after t4. In one example, the controller can calculate the standard deviation of the AFR sensor output before t1 if the exhaust pressure is essentially constant. Then, the exhaust pressure may begin to increase at t1. The controller can then proceed to compare the standard deviation of one or more cycles of the AFR sensor output after t1 to determine the amount of the increase in exhaust pressure. As described above with reference to Fig. As described in section 3, the controller can immediately and continuously update exhaust pressure estimates based on the most recent AFR sensor output. However, in other examples, the controller can update exhaust pressure estimates after a period of time, such as the number of cycles of the AFR sensor output signal, based on the output received during that period.

[0078] Similarly, the standard deviation of the LAMBSE signal can increase with increases in exhaust pressure. Therefore, the control unit can estimate the exhaust pressure based on changes in the standard deviation of the LAMBSE signal in a manner similar to that described above for the AFR sensor output signal. Additionally, the control unit can estimate the exhaust pressure based on changes in one or more of the first amplitude (A). L1 ), the second amplitude (A L2 ) and the deviation of the LAMBSE signal. As the exhaust pressure increases, the first amplitude, the second amplitude, and the deviation of the LAMBSE signal can increase as shown in Fig. 4A is shown.

[0079] If Fig. Figure 4B shows a second embodiment of how the AFR sensor output and / or the LAMBSE signal can be affected under varying exhaust pressures. In the example of Fig. 4B The standard deviation, and therefore the amplitude, of the AFR sensor output and the LAMBSE signal can increase with increases in exhaust pressure. In the example from Fig. 4B However, the AFR sensor output may be skewed towards higher oxygen levels. This means that the amplitude of the peaks and maxima may be larger than that of the troughs and minima. In other words, the AFR sensor output may be shifted towards leaner (more oxygen) values ​​at higher exhaust pressures. Thus, the mean value of the AFR sensor output signal at higher exhaust pressures may be shifted towards a higher oxygen value than the mean value of the AFR sensor output signal at lower exhaust pressures. As in Fig. As shown in Figure 4B, the mean value of the AFR sensor output signal between t2 and t3 is at a lower voltage (registers more oxygen) than the mean value of the AFR sensor output signal before t1.

[0080] Similarly, the mean value of the LAMBSE signal can shift towards a richer value (more fuel) at higher exhaust pressures than the mean value of the LAMBSE signal at lower exhaust pressures. As in Fig. As shown in Figure 4B, the mean value of the LAMBSE signal between t2 and t3 can be richer than the mean value of the LAMBSE signal before t1.

[0081] It should be understood that the AFR sensor output in other examples may be skewed towards lower oxygen levels. Thus, the amplitude of the peaks and maxima may be smaller than that of the troughs and minima. In other words, the AFR sensor output may be shifted towards richer (less oxygen) values ​​at higher exhaust pressures. Therefore, the mean value of the AFR sensor output signal at higher exhaust pressures may be shifted towards a lower oxygen value than the mean value of the AFR sensor output signal at lower exhaust pressures. Similarly, if the AFR sensor output signal is skewed towards lower oxygen values ​​at higher exhaust pressures, the LAMBSE signal may be shifted towards a leaner (less fuel) value than the mean value of the LAMBSE signal at lower exhaust pressures.

[0082] Fig. Figure 4C shows a third embodiment of how the AFR sensor output and / or the LAMBSE signal can be affected under varying exhaust pressures. In the example of Fig. 4C The frequency of the AFR sensor output and the LAMBSE signals can increase with increasing exhaust pressure. Conversely, the wavelength and / or the time interval of the AFR sensor output and the LAMBSE signals can decrease with increasing exhaust pressure. In the example of Fig. However, the amplitude of the AFR sensor output cannot change under varying exhaust pressures. In the example of Fig. 4C The AFR sensor can be a narrowband lambda sensor such as an EGO or HEGO. Therefore, the AFR sensor can become saturated at low exhaust pressures (reaching the peaks and troughs). Conversely, at higher exhaust pressures, the AFR sensor can reach the peaks and troughs more quickly, thus increasing the frequency of the lambda sensor switching cycles. As can be seen between t2 and t3, where the exhaust pressure is higher than before t1, the frequency of the AFR sensor output signal is higher than before t1. However, the amplitude of the AFR sensor output signal may remain approximately the same.

[0083] The Lambse signal can increase in frequency with increasing exhaust pressure and can also increase in standard deviation and / or amplitude with increasing exhaust pressure. As shown in graph 436, the Lambse signal has a higher frequency and a larger standard deviation between t2 and t3 than before t1. Therefore, the first and second amplitudes between t2 and t3 can also be larger than before t1.

[0084] If now Fig. Considered in 4D, this shows a fourth embodiment of how the AFR sensor output and / or the LAMBSE signal can be affected under varying exhaust pressures. In the example of Fig. 4D, the frequency and standard deviation / amplitude of the AFR sensor output and the LAMBSE signals can increase with increases in exhaust pressure. In the example of Fig. 4D, as in the Fig. 4A and Fig. 4B, the AFR sensor can be a broadband lambda sensor such as a UEGO and thus operate in a wider range of oxygen levels than the AFR sensor made of Fig. 4C measures. Thus, the amplitude and / or standard deviation of the AFR sensor outputs can be greater at higher exhaust pressures, such as between t2 and t3, than at lower exhaust pressures, such as before t1. Furthermore, the frequency of the AFR sensor output signal and the LAMBSE signal can increase with increasing exhaust pressure. Thus, the switching frequency of the LAMBSE signal can increase with increasing exhaust pressure. Thus, λ L2 decrease with increases in exhaust pressure.

[0085] If now Fig. Figure 5, which is considered here, shows a graph 500 illustrating exemplary settings for various engine actuators under varying exhaust pressures. For example, in response to increases in exhaust pressure, one or more particulate filter regenerations may be initiated, an intake throttle valve may be set to a more closed position, and / or a wastegate valve may be set to a more open position. Furthermore, graph 500 shows how changes in exhaust pressure can affect the outputs of an AFR sensor, as detailed above with reference to the Fig. 4A-4D described.

[0086] The curve 502 shows changes in a driver-demand torque based on input from a driver via an accelerator pedal (e.g., input device 132, which Fig. (as described in 1) can be estimated. The graph 504 shows changes in exhaust pressure that can be estimated based on one or more of the outputs from an AFR sensor (e.g., the AFR sensor 126, described above in Fig. 1) and / or a fuel injection quantity commanded by a fuel control unit (LAMBSE signal) can be estimated. The threshold value 505 represents a threshold exhaust pressure above which a control unit (e.g., the control unit 12, which is described in Fig. (as described in 1) adjusts various engine actuators to reduce exhaust backpressure. Trace 506 shows changes in the outputs from the AFR sensor, and trace 508 shows changes in the LAMBSE signal. As described above in Fig. As described in section 2, the LAMBSE signal can represent a commanded fuel injection quantity or a desired change in the commanded fuel injection quantity. The dotted line 509 can represent a fuel injection setpoint corresponding to a desired air-fuel ratio (e.g., stoichiometry). Thus, LAMBSE values ​​above the dotted line 509 can correspond to a superstoichiometric mixture, and LAMBSE values ​​below the dotted line 509 can correspond to a substoichiometric mixture.

[0087] The curve 510 shows a load on a particulate filter (e.g., the particulate filter 82, which is shown above in Fig. (as described in Figure 1). The load can correspond to the amount of particles that have accumulated on the filter. The particulate filter load can be estimated based on the amount of time since the last filter regeneration and / or based on a pressure drop across the filter. In other examples, the particulate filter load can be estimated based on the estimated exhaust pressure, which can be estimated based on outputs from the AFR sensor. In particular, as the particulate filter becomes increasingly loaded with particles, the flow through the filter may become more restricted, increasing the exhaust pressure upstream of the filter. Thus, the filter load can increase with increases in exhaust pressure. Graph 512 shows changes in filter regeneration. As above in Fig. As described in Figure 1, the filter can be regenerated by switching on a heater and burning off the particles that have accumulated on the filter. The threshold value 511 can represent a load level of the particulate filter above which filter regeneration can be initiated. The curve 514 shows changes in the position of a wastegate valve (e.g., the wastegate valve 168, which was described above in Figure 1). Fig. 1 is described) and the curve 516 shows changes in the position of an intake throttle (e.g. the intake throttle 62, which is described above in Fig. 1 is described).

[0088] Starting from t1, the driver demand torque may be essentially low. For example, the driver may not depress the accelerator pedal before t1, and the vehicle may be in a fuel-saving mode for deceleration. Thus, no fuel may be injected into the engine before t1. The fuel control may be in open-loop mode before t1. This means that the LAMBSE signal may be generated based on a preset fuel supply quantity (e.g., zero) and may not be based on the output from the AFR sensor. Thus, the intake throttle may be essentially closed, and the mass airflow to the engine may be essentially constant (e.g., zero). In other examples, however, the intake throttle may be set to an open position to reduce pumping losses. Thus, the LAMBSE signal may command no fuel injection. However, the exhaust pressure may increase before t1.Due to the increase in exhaust pressure, the partial pressure of oxygen can increase, and thus the amount of oxygen registered by the AFR sensor can increase. Therefore, the exhaust pressure can be derived based on changes in the AFR sensor output during open-loop fuel control and during steady-state engine operating conditions. As above with reference to... Fig.As explained in section 3, the air mass flow rates and fuel injection rates can remain essentially the same during open-loop fuel control and steady-state engine operating conditions. Thus, changes in the AFR sensor output can be related to changes in exhaust backpressure. However, in further examples, it should be understood that the exhaust backpressure estimate may be frozen and cannot be updated when the control system switches to open-loop air-fuel ratio control. As seen before t1, the AFR sensor output may register more oxygen (e.g., leaner exhaust mixtures) as the exhaust backpressure increases. Due to the DFSO conditions before t1, the wastegate valve may remain open, so the turbocharger remains off. The particulate filter load may be below the threshold of 511, and therefore particulate filter regeneration may be disabled.

[0089] At t1, the driver-demand torque can increase, and the DFSO mode can be deactivated. The intake throttle can be opened, and the wastegate valve can be adjusted to a more closed position to increase the amount of boost provided by the turbocharger. Additionally, at t1, the fuel control can be switched to closed-loop fuel control. From t1 to t8, the exhaust backpressure can be estimated based on the AFR sensor output and / or the LAMBSE signal. Furthermore, from t1 to t8, the engine control unit adjusts engine operating parameters, such as the position of the wastegate and / or intake throttle and particulate filter regeneration, based on the estimated exhaust backpressure. For example, at t3, the control unit actuates an intake throttle actuator to reduce the throttle opening in response to the previous increase in the estimated exhaust backpressure.As a result, the exhaust pressure decreases between t3 and t4. As another example, at t5, the control unit activates particulate filter regeneration in response to the particulate filter load exceeding threshold 511 and the exhaust pressure exceeding threshold 505. In one example, the control unit can activate particulate filter regeneration by activating a particulate filter heater. Once the particulate filter is regenerated, the exhaust pressure decreases. As yet another example, at t7, the control unit increases the wastegate opening in response to the rising exhaust pressure, thereby reducing the exhaust pressure between t7 and t8.

[0090] In this way, exhaust pressure can be estimated based on outputs from an AFR sensor, such as the exhaust gas lambda sensor. Specifically, exhaust pressure can be estimated based on features of the periodic waveform signal output by the AFR sensor during closed-loop fuel control, where the waveform signal features can include one or more of the standard deviation, frequency, and amplitude of the periodic waveform. The waveform signal features can be calculated over a period of time. In some examples, the period can encompass a single cycle of the waveform signal, and in others, it can encompass multiple cycles. Thus, in some examples, the frequency, amplitude, and standard deviation can be calculated for each cycle of the waveform signal, and in others, they can be averaged over multiple cycles.

[0091] The exhaust pressure can then be estimated for the period over which the waveform features were calculated, based on a lookup table that relates one or more of the signal's standard deviation, frequency, and amplitude to the exhaust pressures. In further examples, the exhaust pressure can be estimated based on changes in the waveform features over multiple time periods. That is, the waveform features can be calculated at regular binning intervals, and then the calculated waveform features for each binning interval can be compared to determine changes in the exhaust pressure. The exhaust pressure can increase monotonically with increasing frequency, standard deviation, and amplitude of the waveform signal.

[0092] In some examples, when the commanded fuel injection quantity, calculated during closed-loop fuel control, is based on the raw output from the AFR sensor rather than the pressure-compensated output of the AFR sensor generated by an AFR monitoring module, the exhaust pressure can be estimated additionally or alternatively based on the commanded fuel injection signal (LAMBSE). The exhaust pressure can increase monotonically with increasing switching frequency of the LAMBSE signal. Additionally, the exhaust pressure can increase monotonically with increasing magnitude of change in the LAMBSE signal at a switching point. Furthermore, the exhaust pressure can increase monotonically with increasing deviation or difference between successive minimum and maximum values ​​of the LAMBSE signal.

[0093] A technical cost reduction is achieved by estimating exhaust backpressure based on outputs from an AFR sensor instead of a pressure sensor. Thus, by deriving exhaust backpressure from fluctuations in the AFR sensor outputs, an exhaust backpressure sensor can be omitted from the engine system, reducing both cost and complexity. Furthermore, exhaust backpressure estimates based on AFR sensor outputs can be more accurate than estimates derived from mass airflow, as these estimates account for exhaust constraints such as particulate filter loading.

[0094] In one embodiment, a method comprises monitoring periodic waveform outputs from a fuel controller during closed-loop fuel control; estimating an exhaust pressure based on the controller's waveform outputs; and adjusting at least one engine operating parameter based on the estimated exhaust pressure. In a first example of the method, the controller's waveform outputs include a commanded fuel injection quantity, wherein the waveform outputs are generated by the controller based on feedback from an exhaust gas lambda sensor. A second example of the method optionally includes the first example and further includes, wherein the feedback from the exhaust gas lambda sensor is received directly by the controller from the exhaust gas lambda sensor and comprises a raw output from the exhaust gas lambda sensor that has not been adjusted for pressure by a control module.A third example of the method optionally includes one or more of the first and second examples and further includes, wherein estimating the exhaust pressure based on the waveform outputs comprises estimating the exhaust pressure based on a frequency of the waveform outputs. A fourth example of the method optionally includes one or more of the first to third examples and further includes, wherein the estimated exhaust pressure increases monotonically with increasing frequency of the waveform outputs. A fifth example of the method optionally includes one or more of the first to fourth examples and further includes, wherein estimating the exhaust pressure based on the waveform outputs comprises estimating the exhaust pressure based on a magnitude of change in the waveform outputs at a switching point, and wherein the estimated exhaust pressure increases monotonically with increasing magnitude of change in the waveform outputs at the switching point.A sixth example of the method optionally includes one or more of the first to fifth examples and further includes, wherein estimating the exhaust pressure based on the waveform outputs comprises estimating the exhaust pressure based on a difference between a minimum and a maximum value of a single cycle of the periodic waveform outputs, and wherein the estimated exhaust pressure increases monotonically with increasing differences between the minimum and the maximum values. A seventh example of the method optionally includes one or more of the first to sixth examples and further includes, wherein adjusting the at least one engine operating parameter comprises opening a wastegate valve in response to the exhaust pressure rising above a threshold.An eighth example of the method optionally includes one or more of the first to seventh examples and further includes, wherein the adjustment of the at least one engine operating parameter comprises closing an intake throttle in response to the exhaust pressure rising above a threshold. A ninth example of the method optionally includes one or more of the first to eighth examples and further includes, wherein the adjustment of the at least one engine operating parameter comprises regenerating a particulate filter in response to the exhaust pressure rising above a threshold. A tenth example of the method optionally includes one or more of the first to ninth examples and further includes, wherein the estimation of the exhaust pressure is based on the waveform outputs of the control unit during at least one threshold period, wherein an intake air mass flow remains within a threshold range.

[0095] In a further embodiment, a method for an engine comprises: monitoring periodic waveform outputs from an exhaust air-fuel ratio (AFR) sensor during closed-loop fuel control; estimating an exhaust pressure based on one or more standard deviations and mean frequency of cycles of the periodic waveform outputs; and adjusting at least one engine operating parameter based on the estimated exhaust pressure. In a first example of the method, the method further comprises freezing the estimated exhaust pressure during open-loop fuel control and not updating the estimated exhaust pressure based on one or more standard deviations and the mean frequency of cycles of the periodic waveform outputs.A second example of the method may include the first example and further includes monitoring outputs from the AFR sensor during open-loop fuel control when an intake air mass flow rate is substantially constant; and estimating the exhaust pressure during open-loop fuel control when the intake air mass flow rate is substantially constant, based on changes in an amount of oxygen measured by the AFR sensor, wherein the exhaust pressure increases monotonically with increases in the amount of oxygen measured by the AFR sensor.A third example of the method optionally includes one or more of the first and second examples and further includes estimating the exhaust pressure based on periodic waveform outputs from a fuel controller during closed-loop fuel control, wherein the periodic waveform outputs of the fuel controller are generated based on the periodic waveform outputs from the AFR sensor and not from pressure-compensated outputs from the AFR sensor. A fourth example of the method optionally includes one or more of the first through third examples and further includes, wherein the outputs of the AFR sensor include voltages representing a partial pressure of oxygen in exhaust gases as detected by the AFR sensor, and wherein the outputs of the AFR sensor are direct outputs from the AFR sensor and are not modified or adjusted by a control circuit or module.A fifth example of the procedure may include one or more of the first to fourth examples and further includes, wherein the estimated exhaust pressure increases monotonically with increases of one or more of the standard deviation and the frequency of the cycles of the periodic waveform outputs.

[0096] In yet another embodiment, an engine system comprises: an exhaust gas lambda sensor; one or more fuel injectors; and a controller with computer-readable instructions stored in non-volatile memory for: determining a commanded quantity of fuel to be injected by the one or more fuel injectors based on outputs from the exhaust gas lambda sensor; adjusting the one or more fuel injectors to inject the commanded quantity of fuel; and estimating an exhaust pressure based on one or more of the outputs from the exhaust gas lambda sensor and changes in the commanded quantity of fuel over a period of time.In a first example of the engine system, the engine system further comprises a lambda sensor monitoring module in electrical communication with the lambda sensor and the control unit, wherein the module includes instructions stored in non-volatile memory for adjusting the lambda sensor outputs in response to fluctuations in exhaust pressure, and wherein the commanded quantity of fuel to be injected is determined based on the adjusted lambda sensor outputs generated by the module. A second example of the engine system optionally includes the first example and further comprises, wherein the control unit further includes instructions for estimating the exhaust pressure based only on the lambda sensor outputs and not based on the adjusted lambda sensor outputs generated by the lambda sensor monitoring module.

[0097] It is noted that the exemplary control and estimation routines included herein can be used with various engine and / or vehicle system designs.

[0098] The control procedures and routines disclosed herein can be stored as executable instructions in non-volatile memory and executed by the control system, including the controller in combination with the various sensors, actuators, and other motor hardware. The specific routines described herein can represent one or more of any number of processing strategies, such as event-driven, interrupt-driven, multi-tasking, multi-threading, and the like. Therefore, various illustrated actions, operations, and / or functions can be performed in the illustrated sequence or in parallel, or in some cases, omitted. Likewise, the processing sequence is not strictly necessary to achieve the features and benefits of the exemplary embodiments described herein, but is provided for the convenience of illustration and description.One or more of the illustrated actions, processes, and / or functions can be performed repeatedly, depending on the specific strategy employed. Furthermore, the described actions, processes, and / or functions can graphically represent code that is to be programmed into non-volatile memory of the computer-readable storage medium within the engine control system. The described actions are then executed by carrying out the instructions within a system that includes the various engine hardware components in combination with the electronic control unit.

[0099] It is understood that the interpretations and routines disclosed herein are exemplary and that these specific embodiments are not to be interpreted in a limiting sense, as numerous variations are possible. For example, the foregoing technology can be applied to V6, I4, I6, V12, 4-cylinder boxer, and other engine types. The subject matter of this disclosure includes all novel and non-obvious combinations and sub-combinations of the various systems and interpretations and other features, functions, and / or properties disclosed herein.

[0100] The following claims describe, in particular, certain combinations and subcombinations that are considered novel and not obvious. These claims may refer to "one" element, "a first" element, or the equivalent thereof. Such claims are to be understood as including one or more such elements and neither requiring nor excluding two or more such elements. Further combinations and subcombinations of the disclosed features, functions, elements, and / or properties may be claimed by amending the present claims or by filing new claims in this or a related application.Such patent claims are, moreover, considered to be included in the subject matter of the present disclosure, irrespective of whether they have a broader, narrower, the same or different scope of protection compared to the original claims.

Claims

[1] Procedure, encompassing: Monitoring a periodic waveform output of a fuel control system (202) during closed-loop fuel control over several cycles; Estimating an exhaust pressure based on at least one waveform feature, wherein the at least one waveform feature comprises one or more of the frequency, standard deviation, and amplitude of the periodic waveform output, while maintaining a desired stoichiometric air-fuel ratio of an engine (10); and Setting at least one engine operating parameter based on the estimated exhaust pressure. [2] Method according to claim 1, wherein the periodic waveform output of the fuel control includes a commanded fuel injection quantity (216), and wherein the periodic waveform output is generated by the control (202) based on feedback from an exhaust gas lambda sensor (250), and wherein the periodic waveform output of the fuel control oscillates back and forth between richer and leaner values ​​of the desired stoichiometric air-fuel ratio. [3] Method according to claim 2, wherein the feedback from the exhaust gas lambda sensor (250) is received directly by the fuel control (202) and comprises a raw output provided by the exhaust gas lambda sensor and not pressure-compensated or modified by a control module, wherein the raw output represents a partial pressure of oxygen in the exhaust gases detected by the exhaust gas lambda sensor. [4] Method according to claim 1, wherein estimating the exhaust pressure based on the periodic waveform output comprises estimating the exhaust pressure based on a frequency of the periodic waveform output. [5] Method according to claim 4, wherein the estimated exhaust pressure increases monotonically with increases in the frequency of the periodic waveform output. [6] Method according to claim 1, wherein the estimation of the exhaust pressure based on the periodic waveform output comprises estimating the exhaust pressure based on the magnitude of a change in the periodic waveform output at a switching point, and wherein the estimated exhaust pressure increases monotonically with increases in the magnitude of the change in the periodic waveform output at the switching point. [7] Method according to claim 1, wherein the estimation of the exhaust pressure based on the periodic waveform output comprises estimating the exhaust pressure based on a difference between a minimum value and a maximum value of a single cycle of the periodic waveform output, and wherein the estimated exhaust pressure increases monotonically with increases in the difference between the minimum and the maximum value. [8] Method according to claim 1, wherein the adjustment of the at least one engine operating parameter comprises opening a wastegate valve (168) in response to the exhaust pressure rising above a threshold value. [9] Method according to claim 1, wherein the adjustment of the at least one engine operating parameter comprises closing an intake throttle (62) in response to the exhaust pressure rising above a threshold value. [10] Method according to claim 1, wherein the setting of the at least one engine operating parameter comprises regenerating a particulate filter (82) in response to the exhaust pressure rising above a threshold value. [11] Method according to claim 1, wherein the estimation of the exhaust pressure is based on the periodic waveform output of the fuel control (202) during at least one threshold period, wherein an intake air mass flow (120) remains within a threshold range. [12] Method according to claim 1, wherein estimating the exhaust pressure based on the waveform output comprises estimating the exhaust pressure based on one or more standard deviations and mean frequency of cycles of the periodic waveform outputs, and wherein the method further comprises freezing the estimated exhaust pressure during open-loop fuel control and not updating the estimated exhaust pressure based on one or more standard deviations and frequency of cycles of the periodic waveform outputs. [13] Engine system, comprising: an exhaust gas lambda sensor (126); one or more fuel injection devices (66); and a controller (12) with computer-readable instructions stored in non-volatile memory for the following: Determining a commanded quantity of fuel to be injected by one or more fuel injection devices (66) to maintain a desired stoichiometric air-fuel ratio of the engine system, based on several cycles of a periodic waveform output from the exhaust lambda sensor (126), wherein the periodic waveform output oscillates back and forth over time around a stoichiometric setpoint; Adjusting the one or more fuel injection devices (66) to inject the commanded quantity of fuel; and while maintaining the desired stoichiometric air-fuel mixture, estimating an exhaust pressure based on one or more of the periodic waveform outputs of the exhaust lambda sensor and changes in the commanded amount of fuel over a period of time, wherein the commanded amount of fuel has a periodic waveform and changes in the commanded amount of fuel over the period of time are determined based on a waveform feature of the periodic waveform. [14] Engine system according to claim 13, further comprising a lambda sensor monitoring module (253) which is in electrical communication with the exhaust gas lambda sensor (126) and the control unit (12), wherein the module comprises instructions stored in non-volatile memory for setting the periodic waveform outputs of the exhaust gas lambda sensor in response to fluctuations in exhaust gas pressure, wherein the commanded fuel quantity is determined based on the periodic waveform outputs of the exhaust gas lambda sensor set by the module, and wherein the estimation of the exhaust gas pressure based on one or more of the periodic waveform outputs of the exhaust gas lambda sensor and changes in the commanded fuel quantity are the estimation of the exhaust gas pressure based on the waveform feature which comprises one or more of the following properties: amplitude,Frequency and wavelength of the periodic waveform outputs of the exhaust gas lambda sensor and / or the periodic waveform of the commanded fuel quantity. [15] Engine system according to claim 14, wherein the control (12) further includes instructions for estimating the exhaust pressure only based on the periodic waveform outputs of the exhaust lambda sensor (126) and not based on the set periodic waveform outputs of the exhaust lambda sensor generated by the lambda sensor monitoring module (253).

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