Control unit for a combustion engine

Abstract

A control configuration for a combustion engine includes a control unit which has a function that determines a reference variable by taking into account an operating state information, an upper limit and a cumulative actual variable. The reference variable influences an operating state of the combustion engine such that a plurality of actual variables are adjusted so that, in an operating time period with a combination of arbitrary different operating states of the combustion engine that are set in a random order, cumulative actual variables do not exceed upper limits in this operating time period, wherein a target function is minimized by selecting the reference variable from Pareto-optimal alternatives through use of an indifference curve. A combustion engine and a vehicle are also provided.

Claims

1. A control configuration for a combustion engine, comprising: a control unit programmed to: determine a reference variable defined by at least one of an EGR rate, an EGR distribution, a cylinder filling parameter, a charging pressure, a fuel rail pressure, an injection point in time, and an ignition point in time by taking into account engine operating state information and upper limits of cumulative actual emission variables, wherein said cumulative actual emission variables comprise a plurality of respective actual emission variables that are accumulated over an operating time period during real driving operations of the combustion engine; select said reference variable from Pareto-optimal alternatives through use of an indifference curve by taking into account distances of said cumulative actual emission variables from said upper limits to thereby minimize a target function; and control an operating state of the combustion engine in accordance with the selected reference variable, such that said plurality of respective actual emission variables are adjusted in real-time so that, in said operating time period with a combination of arbitrary different operating states of the combustion engine that are set in a random order, said cumulative actual emission variables do not exceed said upper limits in said operating time period.

2. The control configuration according to claim 1, wherein said target function includes at least one variable selected from the group consisting of an actual emission variable, a fuel consumption and a CO.sub.2 emission.

3. The control configuration according to claim 1, wherein said engine operating state information includes a revolution rate and a setpoint torque.

4. The control configuration according to claim 1, wherein said operating time period and different operating states of a trip are known.

5. The control configuration according to claim 1, wherein said actual emission variables include at least two variables selected from the group consisting of a NOx emission, a HC emission, a CO emission, a CO.sub.2 emission, a combined HO and NOx emission, a carbon black emission, and an AdBlue consumption.

6. The control configuration according to claim 1, wherein at least two actual emission variables are considered.

7. The control configuration according to claim 6, wherein said at least two actual emission variables include a NOx emission and a carbon black emission.

8. A combustion engine comprising: a control unit programmed to: determine a reference variable defined by at least one of an EGR rate, an EGR distribution, a cylinder filling parameter, a charging pressure, a fuel rail pressure, an injection point in time, and an ignition point in time by taking into account engine operating state information and upper limits of cumulative actual emission variables, wherein said cumulative actual emission variables comprise a plurality of respective actual emission variables that are accumulated over an operating time period during real driving operations of the combustion engine; select said reference variable from Pareto-optimal alternatives through use of an indifference curve by taking into account distances of said cumulative actual emission variables from said upper limits to thereby minimize a target function; and control an operating state of the combustion engine in accordance with the selected reference variable, such that said plurality of respective actual emission variables are adjusted in real-time so that, in said operating time period with a combination of arbitrary different operating states of the combustion engine that are set in a random order, said cumulative actual emission variables do not exceed said upper limits in said operating time period.

9. A vehicle including a combustion engine, comprising: a control unit programmed to: determine a reference variable defined by at least one of an EGR rate, an EGR distribution, a cylinder filling parameter, a charging pressure, a fuel rail pressure, an injection point in time, and an ignition point in time by taking into account engine operating state information and upper limits of cumulative actual emission variables, wherein said cumulative actual emission variables comprise a plurality of respective actual emission variables that are accumulated over an operating time period during real driving operations of the combustion engine; select said reference variable from Pareto-optimal alternatives through use of an indifference curve by taking into account distances of said cumulative actual emission variables from said upper limits to thereby minimize a target function; and control an operating state of the combustion engine in accordance with the selected reference variable, such that said plurality of respective actual emission variables are adjusted in real-time so that, in said operating time period with a combination of arbitrary different operating states of the combustion engine that are set in a random order, said cumulative actual emission variables do not exceed said upper limits in said operating time period.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

(1) FIG. 1 is a diagrammatic view of an engine system with a control unit according to the invention;

(2) FIG. 2 shows a schematic representation of input and output variables, as well as the information processing of a control unit according to the invention;

(3) FIG. 3 is a diagram illustrating carbon black and NOx emissions represented as a function of the EGR rate in accordance with the invention;

(4) FIG. 4 is a diagram illustrating Pareto-optimal working points for which a certain carbon black emission and a certain NOx emission apply in accordance with the invention;

(5) FIG. 5 is a diagram illustrating the selection of a reference variable by an indifference curve based on the relationship of carbon black emissions and NOx emissions for a certain (increased) cumulative NOx emission in accordance with the invention;

(6) FIG. 6 is a diagram illustrating the selection represented in FIG. 5 for a lower cumulative NOx emission in accordance with the invention;

(7) FIG. 7 is a diagram illustrating the selection represented in FIG. 5 for an excessive cumulative NOx emission in accordance with the invention;

(8) FIG. 8 is a diagram illustrating the selection represented in FIG. 5 based on the relationship of CO.sub.2 and NOx emissions in accordance with the invention; and

(9) FIG. 9 is a diagram illustrating the selection represented in FIG. 5 by a non-linear indifference curve in accordance with the invention.

DETAILED DESCRIPTION OF THE INVENTION

(10) Referring now to the figures of the drawing in detail and first, particularly, to FIG. 1 thereof, there is shown an engine schematic that is regulated or controlled through the use of a control unit 1 according to the invention. A combustion engine implemented as a reciprocating piston engine 2 (diesel or Otto-cycle engine) is represented, which is filled via valves 3 and via a charging air tract 4 and that is evacuated via an exhaust tract 5. The input air passes through an air filter 6 and an exhaust gas turbocharger 7 with variable turbine geometry, through an intercooler 8 via an inlet valve 3 into the cylinder, where fuel may be injected through the use of an injection system. Following the compression and combustion of the air-fuel mixture, the resulting exhaust gas is discharged through an exhaust valve 3 via the exhaust tract.

(11) During this, the compressed exhaust gas passes through the exhaust gas turbocharger 7, drives the exhaust gas turbocharger and thus compresses the charging air. It then passes through an oxides of nitrogen storage catalytic converter 10 and a diesel particle filter 11 and finally passes through an exhaust flap 12 into the exhaust pipe 13.

(12) The valves 3 are driven via a variable camshaft 14. The adjustment is carried out via a camshaft adjuster 15 that can be actuated by the control unit 1.

(13) Some of the exhaust gas can be fed into the charging air tract 4 via a high-pressure exhaust gas recirculation valve 16. An exhaust gas treated partial flow can be fed via a suitable exhaust gas cooler 17 and an exhaust gas recirculation low pressure valve 18 into the charging air tract 4 in the low-pressure region after the exhaust gas turbocharger 7. The turbine geometry of the exhaust gas turbocharger 7 is adjustable through the use of an actuator 19. The charging air feed (Gas) is regulated through the use of the main throttle flap 20.

(14) Inter alia, the exhaust gas recirculation low pressure valve 18, the actuator 19, the main throttle flap 20, the exhaust gas recirculation high pressure valve 16, the camshaft adjuster 15 and the exhaust flap 12 can be actuated (solid lines) via the control unit 1.

(15) Furthermore, the control unit 1 is supplied with temperature information (intercooler 8, exhaust gas cooler 17) through the use of sensors and setpoint generators for example, and with actual emission values (for example from a sensor or physical/empirical model).

(16) Yet more operating state information can be used for this purpose: accelerator pedal position, choke flap position, air mass, battery voltage, engine temperature, crankshaft revolution rate and top dead center, selected gear and the speed of the vehicle.

(17) There is thus a complex control and regulating system that will adjust, regulate and optimize as far as possible the engine operation in respect of different target variables (command variables) in diverse operating states.

(18) The following exemplary embodiments relate to the control and regulation of emission values depending on predetermined upper emission limits and cumulative actual values.

(19) Such a basic system is represented in FIG. 2. In this case, the control unit 1 determines one or more reference variables x(t) that are necessary and effective for influencing the emissions.

(20) From the reference variables, control variables are derived, which, in the combustion engine 2 or the components thereof (for example position of the main throttle flap 20, camshaft setting, the setting of the turbine geometry of the exhaust gas turbocharger 7, the setting of the exhaust flap 12, etc.), influence the emissions (for example NOx, HC, CO, carbon black) of the combustion engine. The emissions are detected as mass flows (emission rates) Em.sup.DS (for example mass per unit time [mg/s]). From these emissions, cumulative actual values Em.sup.K of the emissions are derived (integration of the emission rates over time).

(21) The reference variable(s) x(t) are determined in the control unit 1 from the cumulative actual values Em.sup.K, together with the elapsed operating time t or the distance covered s, known or predetermined upper emission limits Em.sup.G and information about the driver's intentions FW (for example acceleration: a.sup.Soll; torque: M.sup.Soll) and other operating conditions SB (for example speed: v; revolution rate: n) of the combustion engine 2.

(22) FIG. 3 shows by way of example the relationship between NOx emissions and carbon black emissions as a function of the exhaust gas recirculation rate (EGR), which forms a reference variable x(t) here. The diagram shows that by increasing the EGR the NOx emissions can indeed be reduced, but in doing so the carbon black emissions rise.

(23) FIG. 4 shows a diagram with combinations of reference variables of determined carbon black emissions that are plotted against determined NOx emissions. If the object is now for example to minimize/to reduce the carbon black emissions in an (arbitrary) operating state, but in doing so to conform to a (cumulative) NOx limit value, the emissions history (cumulative actual values Em.sup.G) for past operating states (possibly arbitrary different operating states set in random order) must be taken into account.

(24) Pareto-optimal target variable combinations, for which the carbon black emission can only be lowered further if the NOx emission is increased, are identified by the x points. All Pareto-optimal target variable combinations form the so-called Pareto front, which connects the x points to each other. In the case of a minimization problem, points to the left below the Pareto front (hatched region) cannot be achieved and all target variable combinations provided on the right and above are not Pareto-optimal, because in each case there are combinations (x points) that can be more favorably achieved on the Pareto front, both with respect to carbon black emissions and NOx emissions.

(25) The representation in FIG. 5 shows the selection of two target variables (NOx emissions and carbon black emissions) from Pareto-optimal target variable combinations. In the column on the right, a NOx limit value NOx-G (dashed line) is indicated as the upper emission limit Ems and the column represented below this shows the NOx emissions NOx-K.sub.1 accumulated so far in the hatched region as the cumulative actual value Em.sup.K. Because the cumulative NOx emissions NOx-K.sub.1 are already relatively close to the NOx limit value NOx-G, a relatively high exchange ratio between the target variables carbon black emissions and NOx emissions is selected here (increased carbon black emissions, benefiting low NOx), in order not to exceed the NOx limit value NOx-G. The desired exchange ratio is indicated by the indifference curve I here, which is shown decreasing relatively steeply here, and is then shifted to the nearest target variable combination, in which a certain carbon black emission and a certain NOx emission can be achieved for this operating point. The target variable combination is then assigned an EGR as a suitable Pareto-optimized reference variable x(t) using the information known from the diagram of FIG. 3.

(26) FIG. 6 shows an example in which cumulative NOx emissions (NOx-K.sub.2) lie further below the NOx limit value NOx-G. Here the exchange ratio of the indifference curve I is smaller (the straight line decreases less steeply). Here a higher NOx emission can thus be accepted without a risk of the NOx limit value NOx-G being exceeded. Thus, the carbon black emission can be kept lower. The more gently sloping straight line is shifted to the next target variable combination, at which a certain NOx emission and a corresponding carbon black emission can be achieved with an associated reference variable x(t) (here the corresponding EGR of FIG. 3).

(27) FIG. 7 shows an example in which the cumulative NOx emissions (NOx-K.sub.3) have exceeded the NOx limit value NOx-G. Here the exchange ratio of the straight lines I (vertical indifference curve) is quasi infinite. Regardless of the level of the carbon black emissions, the reference variable x(t) is selected for minimal NOx emissions.

(28) FIG. 8 shows, similarly to FIG. 5, an example in which CO.sub.2 will be minimized depending on the cumulative NOx emissions.

(29) FIG. 9 shows, similarly to FIG. 5, an example in which the indifference curve is not linear.

(30) With the approach illustrated, the emission values (target functions) can be improved during operation and depending on changing boundary conditions. In addition to the problems illustrated here, for which emission variables have been considered in pairs, the method can also be extended to multi-dimensional problems. Thus for example, it is possible to determine Pareto-optimized reference variables x(t) for multiple combinations (for example for CO.sub.2 emissions, carbon black emissions and NOx emissions). In addition to the reference variable EGR, other reference variables x(t) can be determined as Pareto-optimized for regulation (for example VTG position or rail pressure).

LIST OF REFERENCE CHARACTERS

(31) 1 control unit 2 reciprocating piston engine 2a gearbox 3 valves 4 charging air tract 5 exhaust tract 6 air filter 7 exhaust gas turbocharger 8 intercooler 9 cylinder 10 NOx storage catalytic converter 11 diesel particle filter 12 exhaust flap 13 exhaust pipe 14 camshaft 15 camshaft adjuster 16 EGR high pressure valve 17 exhaust gas cooler 18 EGR low pressure valve 19 actuator 20 main throttle flap x(t) reference variable NOx-G limit value NOx-K.sub.1 cumulative actual value FW driver's intentions SB other operating conditions EM.sup.G upper emission limit EM.sup.K cumulative emission values EM.sup.DS emission throughputs I indifference curve