Patent ID: 12188403

DETAILED DESCRIPTION

FIG.1shows an internal combustion engine1according to the present disclosure, in which a fuel mass flow W_F is converted into mechanical power P_mech. For this purpose, a crankcase2of internal combustion engine1includes multiple combustion chambers3in which the fuel is combusted in a known manner. In the present case, internal combustion engine1includes four combustion chambers3.

Internal combustion engine1includes an intake duct4via which individual combustion chambers3are supplied with fresh air for the combustion of the fuel. In the area of an intake manifold5, intake duct4branches from a central duct into four individual streams, each of which is connected to a combustion chamber3.

A compressor18of an exhaust gas turbocharger17is situated in intake duct4. Charge air from the surroundings, at atmospheric pressure P_0and ambient temperature T_0, is drawn in and compressed via compressor18. Atmospheric pressure P_0is measured via an atmospheric pressure sensor, and ambient temperature T_0is measured via an ambient temperature sensor. Directly downstream from compressor18, the pressure of the charge air assumes value P_18, and the temperature of the charge air assumes value T_18.

Also situated in intake duct4, downstream from compressor18, is a charge air cooler7, with the aid of which the charge air may be cooled in a known manner.

In the area directly upstream from intake manifold5, intake duct4includes a measuring point6at which charge pressure P_6is ascertained with the aid of a charge pressure sensor, and charge air temperature T_6is ascertained with the aid of a charge air temperature sensor. Intake manifold5is supplied with a fresh air mass flow W_in.

Combustion chamber [sic]1also includes an exhaust duct8via which exhaust gas mass flow W_out, which results from the combustion of fuel in combustion chamber3, may be discharged. Provided in exhaust duct8is an exhaust manifold9in which individual streams, each connected to a combustion chamber3, are combined into a central duct.

In the area directly downstream from exhaust manifold9, exhaust duct8includes a measuring point10in the central duct, at which exhaust gas pressure P_10is ascertained with the aid of a first exhaust gas pressure sensor, and exhaust gas temperature T_10is ascertained with the aid of a first exhaust gas temperature sensor. Exhaust gas pressure P_10may also be referred to as the exhaust gas back pressure. Alternatively, exhaust gas temperature T_10may be ascertained indirectly with the aid of a state observer, using further measured values.

Downstream from measuring point10, exhaust duct8branches into a turbine duct11and a bypass duct12. Exhaust gas mass flow W_out is accordingly divided between turbine duct11and bypass duct12, an exhaust gas mass flow W_T flowing through turbine duct11, and an exhaust gas mass flow W_WG flowing through bypass duct12.

A turbine19of exhaust gas turbocharger17is situated in turbine duct11. Turbine19is connected to compressor18via a shaft20. Turbine19withdraws energy from exhaust gas mass flow W_out in a known manner in order to drive compressor18via shaft20. Rotational speed n_17of shaft20may be simulated via a state observer, or measured with the aid of a rotational speed sensor.

Directly downstream from turbine19, the pressure of exhaust gas mass flow W_T flowing through turbine duct11assumes value P_19, and the temperature of exhaust gas mass flow W_T flowing through turbine duct11assumes value T_19.

A bypass valve13is situated in bypass duct12. Bypass valve13may also be referred to as a wastegate. Bypass valve13may be infinitely adjusted between a closed position in which bypass valve13is maximally closed, and which may also be referred to as a minimum operating manipulated variable, and an open position in which bypass valve13is maximally open, and which may also be referred to as a maximum operating manipulated variable. The particular manipulated variable of bypass valve13is referred to as bypass valve positionξ_WG. Exhaust gas mass flow W_WG flowing through bypass duct12may be adjusted by opening or closing bypass valve13. In other words, the portion of exhaust gas mass flow W_out flowing through bypass duct12may be adjusted by opening or closing bypass valve13. Bypass valve position WG is measured by a bypass valve position sensor, for example a rotation angle sensor.

Directly downstream from bypass valve13, the pressure of exhaust gas mass flow W_WG flowing through bypass duct12assumes value P_13, and the temperature of exhaust gas mass flow W_WG flowing through bypass duct12assumes value T_13.

Downstream from turbine19and downstream from bypass valve13, turbine duct11and bypass duct12are combined into a collection point14. An exhaust gas flap15is situated in exhaust duct8, downstream from collection point14. Exhaust gas flap15may be infinitely adjusted between a closed position in which exhaust gas flap15is maximally closed, and which may also be referred to as a maximum operating manipulated variable, and an open position in which exhaust gas flap15is maximally open, and which may also be referred to as a minimum operating manipulated variable. The particular manipulated variable of exhaust gas flap15is referred to as exhaust gas flap positionξ_AK. Exhaust gas flap positionξ_AK is measured by an exhaust gas flap position sensor, for example a rotation angle sensor.

In the area directly in front of (upstream from) exhaust gas flap15, the exhaust gas mass flow has a pressure having value P_15′, which is ascertained by a second exhaust gas pressure sensor or simulated by a state observer, and a temperature having value T_15′, which is ascertained by a second exhaust gas temperature sensor.

In the area directly behind (downstream from) exhaust gas flap15, the exhaust gas mass flow has a pressure having value P_15, which is ascertained by a third exhaust gas pressure sensor or simulated by a state observer, and a temperature having value T_15, which is ascertained by a third exhaust gas temperature sensor.

The second exhaust gas pressure sensor and the third exhaust gas pressure sensor may be used in combination, or as alternatives. The second exhaust gas temperature sensor and the third exhaust gas temperature sensor may be used in combination, or as alternatives.

In the present case, an exhaust aftertreatment system16is situated downstream from exhaust gas flap15. Exhaust aftertreatment system16includes a particulate filter24that removes particles, in particular soot particles, from the exhaust gas mass flow in a known manner. Temperature T_24of particulate filter24is measured by a particulate filter temperature sensor or simulated by a suitable temperature model.

Exhaust aftertreatment system16also includes an SCR catalytic converter26that removes nitrogen oxides from the exhaust gas mass flow in a known manner via selective catalytic reduction. Temperature T_26of SCR catalytic converter26is measured by a catalytic converter temperature sensor or simulated by a suitable temperature model.

Situated between particulate filter24and SCR catalytic converter26is an SCR metering system25, with the aid of which ammonia, for example in the form of urea, may be metered into exhaust duct8or into SCR catalytic converter26. Temperature T_25of SCR metering system25is measured by a metering system temperature sensor or simulated by a suitable temperature model.

Internal combustion engine1includes a control unit21, which may also be referred to as a computer, with the aid of which internal combustion engine1is controllable. Control unit21is designed to detect a state vector {circumflex over (x)} of internal combustion engine1. State vector {circumflex over (x)} may encompass, for example, one or multiple values of the power requirement of the internal combustion engine, the fuel mass flow, crankshaft rotational speed n_mot, exhaust gas turbocharger rotational speed n_17, bypass valve positionξ_WG, exhaust gas flap position ξ_AK, fuel-air ratio2, ambient pressure P_0, ambient temperature T_0, pressure of charge air P_18, charge pressure P_6, exhaust gas pressure P_10, temperature of charge air T_18, charge air temperature T_6, exhaust gas temperature T_10, temperature T_19of the exhaust gas mass flow flowing through turbine duct11, temperature T_13of the exhaust gas mass flow flowing through bypass duct12, particulate filter temperature T_24, the temporal profile of the soot mass flow in particulate filter24, the particle loading of particulate filter24, and the nitrogen oxides loading of SCR catalytic converter26.

Control unit21may be designed in such a way that one or multiple values of state vector {circumflex over (x)} may be simulated as a function of further values of state vector {circumflex over (x)}, based on state observers. In addition, control unit21is switched off [sic] to simultaneously regulate exhaust gas temperature T_15and charge pressure P_6. Control unit21is also switched off [sic] to set bypass valve positionξ_WG and exhaust gas flap positionξ_AK.

FIG.2illustrates one embodiment of a method according to the present disclosure for simultaneously regulating the exhaust gas temperature and the charge pressure of an internal combustion engine, with reference to a flowchart. In the present case, the method is explained for the internal combustion engine described above.

Actual charge pressure P_6_actual is ascertained at actual point in time to in a method step V10. Actual charge pressure P_6_actual is measured by the charge pressure sensor. Alternatively, actual charge pressure P_6_actual may be ascertained as a function of actual exhaust gas turbocharger rotational speed n_17_actual, using a state observer.

The actual exhaust gas temperature at actual point in time t0is ascertained in a further method step V20. In the present case, the actual exhaust gas temperature is ascertained downstream from exhaust gas flap15and upstream from exhaust aftertreatment system16by a third exhaust gas temperature sensor. In this case, the actual exhaust gas temperature thus corresponds to value T_15_actual. Alternatively, the actual exhaust gas temperature may be ascertained directly upstream from exhaust gas flap15by the second exhaust gas temperature sensor. In this case, the actual exhaust gas temperature thus corresponds to value T_15′_actual.

A setpoint charge pressure P_6_setpoint at a point in time t0+T subsequent to actual point in time to is determined in a further method step V30. Actual point in time t0and subsequent point in time t0+T delimit a prediction horizon having duration T. Setpoint charge pressure P_6_setpoint is determined for the entire prediction horizon. This may take place as a function of crankshaft rotational speed n_mot and/or of fuel mass flow W_F.

A setpoint range of exhaust gas temperature T_15(or of exhaust gas temperature T_15′) for the prediction horizon, which may also be referred to as the setpoint exhaust gas temperature range, is determined in a further method step V40. For this purpose, a setpoint minimum exhaust gas temperature T_15_min of exhaust gas temperature range is determined.

For determining setpoint minimum exhaust gas temperature T_15_min of the setpoint exhaust gas temperature range, a minimum temperature T_24_min of particulate filter24is determined as a function of the actual soot loading of particulate filter24at actual point in time t0and/or of actual temperature T_24_actual of particulate filter24at actual point in time to.

For determining setpoint minimum exhaust gas temperature T_15_min of the setpoint exhaust gas temperature range, in addition a minimum temperature T_26_min of SCR catalytic converter26is determined as a function of the actual ammonia loading of SCR catalytic converter26at actual point in time to.

For determining setpoint minimum exhaust gas temperature T_15_min of the setpoint exhaust gas temperature range, in addition a maximum temperature T_26_max of SCR catalytic converter26is determined as a function of actual temperature T_26_actual at actual point in time t0and of a maximum allowable temperature gradient dT26_max of SCR catalytic converter26. Temperature gradient dT26_max describes the change over time of a mean temperature T_26_mean of SCR catalytic converter26.

For determining setpoint minimum exhaust gas temperature T_15_min of the setpoint exhaust gas temperature range, in addition a minimum temperature T_25_min of SCR metering system25is determined. This takes place as a function of a setpoint reducing agent mass flow of SCR metering system25for the prediction horizon.

For determining setpoint minimum exhaust gas temperature T_15_min of the setpoint exhaust gas temperature range, a comparative value is determined from the maximum value of minimum temperature T_24_min of particulate filter24, minimum temperature T_26_min of SCR catalytic converter26, and minimum temperature T_25_min of SCR metering system25.

Optionally, setpoint minimum exhaust gas temperature T_15_min of the exhaust gas temperature range may be set to the minimum value of the comparative value and maximum temperature T_26_max of SCR catalytic converter26.

Manipulated variable ξ_WG of bypass valve13and manipulated variable ξ_AK of the exhaust gas flap are simultaneously determined in a further method step V50. This takes place with the aid of a nonlinear model-predictive controller as a function of actual charge pressure P_6_actual, of actual exhaust gas temperature T_15_actual, of setpoint charge pressure P_6_setpoint, and of the setpoint exhaust gas temperature range.

The nonlinear model-predictive controller simulates charge pressure P_6_pred at one or multiple subsequent points in time in the prediction horizon as a function of manipulated variable ξ_WG of the bypass valve and of manipulated variable ξ_AK of the exhaust gas flap. The nonlinear model-predictive controller simulates exhaust gas temperature T_15_pred at one or multiple subsequent points in time in the prediction horizon as a function of manipulated variable ξ_WG of bypass valve13and of manipulated variable ξ_AK of exhaust gas flap15.

The nonlinear model-predictive controller minimizes a quality function, the quality function being a function based on the difference between setpoint charge pressure P_6_setpoint and predicted charge pressure P_6_pred at the one or multiple subsequent points in time. The quality function is also a function based on the difference between the setpoint exhaust gas temperature range and predicted exhaust gas temperature T_15_pred at the one or multiple subsequent points in time. The difference between the setpoint exhaust gas temperature range and predicted exhaust gas temperature T_15_pred is set to zero when predicted exhaust gas temperature T_15_pred is in the setpoint exhaust gas temperature range.

The nonlinear model-predictive controller minimizes the quality function, taking the following constraints into account.

Rotational speed n_17of exhaust gas turbocharger17must not exceed maximum rotational speed n_17_max of exhaust gas turbocharger17.

Exhaust gas pressure P_10must not exceed maximum exhaust gas back pressure P_10_max.

Exhaust gas temperature T_10at measuring point10must not exceed maximum exhaust gas temperature T10_max in exhaust duct8.

Exhaust gas temperature T_19directly downstream from turbine19of exhaust gas turbocharger17must not exceed a maximum exhaust gas temperature T_19_max at turbine19of exhaust gas turbocharger17.

Fuel-air ratio λ in combustion chamber3must not fall below minimum fuel-air ratio λ_min.

Manipulated variable ξ_AK of exhaust gas flap15must not exceed a maximum manipulated variable ξ_AK_max. Maximum manipulated variable ξ_AK_max of exhaust gas flap15is determined as a function of predicted exhaust gas temperature T_15_pred. Maximum manipulated variable ξ_AK_max of exhaust gas flap15is set to a maximum operating manipulated variable ξ_AK_1for which exhaust gas flap15is maximally closed, when predicted exhaust gas temperature T_15_pred is below the setpoint exhaust gas temperature range.

In addition, maximum manipulated variable ξ_AK_max of exhaust gas flap15is set to a minimum operating manipulated variable ξ_AK_0for which the exhaust gas flap is maximally open, when the predicted exhaust gas temperature is in the setpoint exhaust gas temperature range or thereabove, as illustrated by the dashed line inFIG.3. Alternatively, as illustrated by the solid line inFIG.3, maximum manipulated variable ξ_AK_max of exhaust gas flap15may be set to a value between maximum operating manipulated variable ξ_AK_1and minimum operating manipulated variable ξ_AK_0when the predicted exhaust gas temperature is in the setpoint exhaust gas temperature range or thereabove. The value continuously decreases in the direction of the minimum operating manipulated variable with an increasing difference between predicted exhaust gas temperature T_15_pred and setpoint minimum exhaust gas temperature T_15_min.

Manipulated variable ξ_WG of bypass valve13is set via a first actuator, and manipulated variable ξ_AK of exhaust gas flap15is set via a second actuator, in a further method step V60.

The method according to the present disclosure is implemented on control unit21.

The method is described in a simplified form inFIG.4with reference to a control loop. Setpoint minimum exhaust gas temperature T_15_min is determined from state vector {circumflex over (x)} of internal combustion engine1, based on above-described ascertainment23of the setpoint exhaust gas temperature range, and is transferred to model-predictive controller MPC. In addition, setpoint charge pressure P_6_setpoint is determined from state vector {circumflex over (x)} of internal combustion engine1, based on above-described ascertainment23′ of setpoint charge pressure P_6_setpoint, and is transferred to the model-predictive controller.

Actual charge pressure P_6_actual and actual exhaust gas temperature T_15_actual are ascertained and transferred to model-predictive controller MPC. Model-predictive controller MPC simultaneously determines manipulated variable ξ_WG of bypass valve13and manipulated variable ξ_AK of exhaust gas flap15as a function of actual charge pressure P_6_actual, of actual exhaust gas temperature T_15_actual, of setpoint charge pressure P_6_setpoint, and the setpoint exhaust gas temperature range having setpoint minimum exhaust gas temperature T_15_min.

Via controlled system22, new values for charge pressure P_6and exhaust gas temperature T_15once again result for a subsequent point in time.

LIST OF REFERENCE NUMERALS

1internal combustion engine2crankcase3combustion chambers4intake duct5intake manifold6measuring point7charge air cooler8exhaust duct9exhaust manifold10measuring point11turbine duct12bypass duct13bypass valve14collection point15exhaust gas flap16exhaust aftertreatment system17exhaust gas turbocharger18compressor19turbine20shaft21control unit22controlled system23ascertainment23[sic] ascertainment24particulate filter25SCR metering system26SCR catalytic converterT_temperatureP_pressure{circumflex over (x)} state vector of the internal combustion engine