DE102006022148B4 - Method for controlling the total air mass to be supplied to an internal combustion engine - Google Patents

Abstract

Method for controlling an internal combustion engine of a motor vehicle, wherein the internal combustion engine (2) has an intake tract (4) on the inlet side and an exhaust tract (6) on the outlet side, and a controllable exhaust gas turbocharger device (10) with a compressor (10b) in the intake tract (4) and a turbine (10a) in the exhaust gas tract (6) and a controllable exhaust gas recirculation device (8) for controlling an exhaust gas recirculation flow (M _EGR ) are present, with the following process steps:
- Determining a desired exhaust gas recirculation flow (M _EGR ), a turbine ( _{10 a} ) acting on the desired exhaust gas flow (M _VTG ) and a target exhaust gas pressure (P _{ENG_OUT} ) in the exhaust system in dependence
◯ a target fresh air mass (MAIR_SOLL) and a target boost pressure (p _{ENG_IN_SOLL} ) or
◯ two desired variables correlating with the desired fresh air mass (MAIR_SOLL) and the desired boost pressure (p _{ENG_IN_SOLL} );
depending on the desired exhaust gas recirculation flow (M _EGR ) and the target exhaust gas pressure (PENG_OUT), determining a first pilot control quantity (SW1) of a first control loop (RK1) using a first calculation model (M1), wherein the first control loop (RK1) has a first manipulated variable (S _EGR ) for controlling the exhaust gas recirculation device (8) generated; and
in dependence on the desired exhaust pressure (p _{ENG_OUT} ) and the desired exhaust gas flow (M _VTG ), determining a second pilot control variable (SW2) of a second control loop (RK2) using a second calculation model (M2), wherein the second control loop (RK2) generates a second manipulated variable (S _VTG ) for controlling the exhaust gas turbocharger device (10).

Description

The invention relates to a method for controlling the gas mass to be supplied to an internal combustion engine in an internal combustion engine of a motor vehicle having an exhaust gas charging device and an exhaust gas recirculation device according to the preamble of claim 1.

There are currently known motor vehicles with internal combustion engines with an exhaust gas turbocharger and an exhaust gas recirculation device, in which the control of the (to be supplied to the internal combustion engine) gas mass in two separate control circuits takes place in different operating ranges. In a first operating range, the so-called exhaust gas recirculation operating range, the regulation of the actual fresh air mass to the desired fresh air mass is effected by a first regulator controlling the valve of the exhaust gas recirculation device. In this operating range, the control of the exhaust gas turbocharger (and thus of the boost pressure) takes place (and thus essentially the gas mass which is supplied to the internal combustion engine) in accordance with a stored characteristic map. In a second operating range, outside of the exhaust gas recirculation control range, the control of the actual boost pressure (pressure in the intake tract in the region of the intake ducts or in the intake manifold / air collector) to a target boost pressure by the exhaust gas turbocharger controlling second controller, while the valve of the Exhaust gas recirculation device (and thus the fresh air mass) is controlled map-dependent or is transferred to the closed state. Such a system is implemented in the current BMW diesel vehicles with turbocharger and exhaust gas recirculation system. Under favorable conditions, it is possible with this system to regulate both setpoints fresh air mass and boost pressure in subregions by the two independent controllers. The disadvantage, however, is that the performance of the controller can not be fully utilized (artificially limited) to avoid unwanted vibrations or interactions between the two controllers.

In the publication DE 10 2005 015 609 A1 a device for controlling an internal combustion engine is described. The internal combustion engine has an exhaust gas turbocharger, which comprises an exhaust gas turbocharger actuator. It also has an exhaust gas recirculation device, which comprises an exhaust gas recirculation valve. An exhaust-gas turbocharger regulator is provided, which determines a control actuating variable exhaust backpressure as a function of the desired boost pressure and an actual boost pressure. Further, an exhaust gas recirculation controller is provided which determines a control manipulated variable exhaust gas recirculation mass flow depending on a desired air mass flow and an actual air mass flow. For each controller, a pilot control is provided in each case. Furthermore, two decoupling units are provided to decouple the two control circuits. In addition, a first conversion unit for determining an exhaust-gas turbocharger actuating signal is provided. It includes a block with an inverse physical model of the exhaust side of the charge. The model is designed so that an input signal for a block is determined by means of the sum of the pre-control manipulated variable exhaust back pressure and the control manipulated variable exhaust back pressure, the decoupling mass flow and preferably at least one further operating variable of the internal combustion engine. In addition, a second conversion unit is provided, which is designed to determine an exhaust gas recirculation valve control signal, depending on the pilot control manipulated variable exhaust gas recirculation mass flow, the control manipulated variable exhaust gas recirculation mass flow, the decoupling exhaust backpressure and preferably at least one operating variable of the internal combustion engine. The second conversion unit comprises a block comprising an inverse physical model of the exhaust gas recirculation device. By means of this inverse physical model of the exhaust gas recirculation device is a position to be set of the exhaust gas recirculation valve or to be set opening degree of the exhaust gas recirculation valve can be determined. The model is dependent on the pilot control manipulated variable exhaust gas recirculation mass flow, the control manipulated variable exhaust gas recirculation mass flow, the decoupling exhaust backpressure and preferably at least one operating variable, for example a pressure ratio of the pressure downstream and upstream of the exhaust gas recirculation valve and / or the temperature of the gas upstream of the exhaust gas recirculation valve is.

The prior art is further referred to the document "charge detection for supercharged diesel engines", H.-G. Nitzke, T. Rebol, in VDI Reports, No. 1672, 2002, p 317 directed.

The invention has for its object to provide a method for controlling the gas to be supplied to an internal combustion engine and the composition of the supplied gas (engine filling: amount and composition of exhaust gas and fresh air) in an internal combustion engine with exhaust gas charger device and exhaust gas recirculation device, in which improves the performance is. In particular, the described disadvantages are to be eliminated and a control in a wider operating range of the internal combustion engine without interference be enabled.

According to the invention the object is achieved by the totality of the features of claim 1, while in the dependent claims preferred embodiments of the invention are given.

• - Bestimmen eines Soll-Abgasrückführstromes, eines die Turbine beaufschlagenden Soll-Abgasstromes und eines Soll-Abgasdrucks im Abgastrakt in Abhängigkeit einer Soll-Frischluftmasse und eines Soll-Ladedrucks oder im Fall einer alternativen Ausgestaltung in Abhängigkeit zweier mit der Soll-Frischluftmasse und dem Soll-Ladedruck korrelierender Soll-Größen;
• - in Abhängigkeit des Soll-Abgasrückführstromes und des Soll-Abgasdrucks, Bestimmen einer ersten Vorsteuergröße eines ersten Regelkreises unter Verwendung eines ersten Berechnungsmodells, wobei der erste Regelkreis eine erste Stellgröße zur Steuerung der Abgasrückführeinrichtung erzeugt; und
• - in Abhängigkeit des Soll-Abgasdrucks und des Soll-Abgasstromes, Bestimmen einer zweiten Vorsteuergröße eines zweiten Regelkreises unter Verwendung eines zweiten Berechnungsmodells, wobei der zweite Regelkreis eine zweite Stellgröße zur Steuerung der Abgasturboladereinrichtung erzeugt.

In the method according to the invention for controlling an internal combustion engine of a motor vehicle, it is assumed that the internal combustion engine has an intake tract on the intake side and an exhaust tract on the exhaust side, and a controllable exhaust gas turbocharger device with a compressor in the intake tract and a turbine in the exhaust gas tract and a controllable exhaust gas recirculation system for controlling an exhaust gas recirculation flow. The method comprises the following method steps:

• Determining a desired exhaust gas recirculation flow, a desired exhaust gas flow acting on the turbine and a desired exhaust gas pressure in the exhaust gas tract as a function of a desired fresh air mass and a desired boost pressure or in the case of an alternative embodiment as a function of two with the desired fresh air mass and the desired Boost pressure of correlated desired quantities;
• in dependence on the desired exhaust gas recirculation flow and the desired exhaust gas pressure, determining a first pilot control variable of a first control loop using a first calculation model, the first control loop generating a first control variable for controlling the exhaust gas recirculation device; and
• in dependence on the desired exhaust gas pressure and the desired exhaust gas flow, determining a second pilot control variable of a second control loop using a second calculation model, the second control loop generating a second control variable for controlling the exhaust gas turbocharger device.

It is advantageous if the first manipulated variable and the second manipulated variable are each determined from a manipulated variable of a regulator of the first control loop or second control loop and the first pilot control variable or second pilot control variable. Alternatively, the respective manipulated variable of a regulator of the first control loop or second control loop can be switched as an additional input variable to the input of the first calculation model or second calculation model.

• 1: in schematischer Darstellung den Aufbau einer Brennkraftmaschine mit Abgasladereinrichtung und Abgasrückführeinrichtung nebst entsprechender Logikeinheit zur Durchführung des erfindungsgemäßen Verfahrens, und
• 2: ein Blockschaltbild zur Veranschaulichung des erfindungsgemäßen Verfahrens bzw. zur Veranschaulichung der Arbeitsweise der Logikeinheit gemäß 1.

An embodiment of the invention is illustrated in the drawing and will be described in more detail below. Show it:

• 1 in a schematic representation of the structure of an internal combustion engine with exhaust gas charger device and exhaust gas recirculation device together with a corresponding logic unit for carrying out the method according to the invention, and
• 2 : a block diagram for illustrating the method according to the invention or for illustrating the mode of operation of the logic unit according to FIG 1 ,

1 shows an internal combustion engine 2 with an inlet-side intake tract 4 , an exhaust-side exhaust tract 6 , one the exhaust tract 6 with the intake tract 4 connecting exhaust gas recirculation device 8th with a controllable exhaust gas recirculation valve 8a , a controllable exhaust gas charger device 10 and a logic unit 12 for controlling the exhaust gas recirculation device 8th and the exhaust gas charger 10 ,

The arrangement shows only the schematic structure of an internal combustion engine 2 with the essential components for the explanation of the invention. Other components, such as a throttle, a charge air cooler, an exhaust gas recirculation cooler, a catalyst or a particulate filter have been omitted for clarity. A fuel supply device in the form of an injection system or the like is not shown for these reasons - taking into account the effects of the components not shown, in particular the cooling of the air and exhaust gas masses and the injected fuel mass always considered when considering the mass ratios in the control processes.

According to the invention, the control of the internal combustion engine takes place 2 supplied gas mass M _{ENG_IN} as well as the composition of these from fresh air M _HFM and recirculated exhaust gas M _EGR in that, in a first control loop, the composition of the gas mass M _{ENG_IN} depending on the fresh air mass supplied on the intake side (and detected via a hot film sensor HFM) M _HFM by controlling the exhaust gas recirculation valve 8a is set or adjusted to a predetermined desired value. As a result, a change in the exhaust gas recirculation flow inevitably occurs M _EGR , which in turn inevitably causes the turbine 10a the exhaust gas charger device 10 driving exhaust mass M _VTG and with it on the turbine 10a acting exhaust pressure p _{ENG_OUT} is changed. According to the invention, the boost pressure is in a second control loop P _{ENG_IN} depending on the turbine 10a acting exhaust gas mass M _VTG or the turbine 10a acting exhaust gas pressure p _{eng_out} by controlling the exhaust gas charger device 10 adjusted such that one due to the change in the exhaust gas recirculation flow M _EGR occurring change in the boost pressure p _{ENG_IN} in the intake tract 4 is compensated. That is, one, due to the control of the exhaust gas recirculation valve 8a Induced change in boost pressure p _{ENG_IN} (or a change in the supplied gas mass M _{ENG_IN} ) in the intake tract 4 , by a timely or even a time-anticipatory control of the exhaust gas charger device 10 is compensated - virtually at the same time or preventively (in advance) a counter-rule action takes place. Also leads a changing control signal to the Abgasladereinrichung 10 to a change in the exhaust pressure p _{ENG_OUT} , resulting in a change of fresh air mass M _HFM , Boost pressure p _{ENG_IN} as well as gas mass M _{ENG_IN} results. There is therefore at the same time a control intervention of the exhaust gas recirculation device 8th depending on exhaust pressure p _{ENG_OUT} , boost pressure p _{ENG_IN} and fresh air mass M _HFM to change the composition of the gas mass M _{ENG_IN} compensate.

The exhaust gas charger device 10 can by adjusting the turbine blades of the turbine 10a and / or by controlling by-pass valves of the turbine 10a and / or the compressor 10b be controlled in their capacity, while the control of the exhaust gas recirculation device 10 by the adjustment of the example formed as an electromagnetic or pneumatic control valve exhaust gas recirculation valve 8a he follows.

In a particularly preferred embodiment of the invention, the control of the internal combustion engine takes place 2 supplied gas mass M _{ENG_IN} (or the regulation of their composition) according to a so-called flatness-based control. For the realization of the control method of the flatness-based control, two conference papers ( 1. M. Fliess, J. L'evine, Ph. Martin, F. Ollivier, P. Rouchon - controlling nonlinear systems by flatness - in CI Byrnes, editor, Systems and Control in the Twenty-Firts Century, page 137-154, Boston, 1997; 2 , Martin, RM Murray, P. Rouchon - Flat Systems - G. Bastin and M. Gevers, editors, Plenary Lectures and Minicourses - Proc. ECC 97, page 211-264, Brussels, 1997 ), which in this respect are fully included in the disclosure of this application. The flatness-based control method is a nonlinear control method. Systems to be controlled by the flatness-based control method must meet certain criteria in order for such a scheme to be feasible at all. By a corresponding reduction of the physical model of the internal combustion engine described above 2 In addition to components, the system requirements were met. In particular, the system has been reduced for this to the following minimum (state) sizes: loader state (speed or an equivalent size) and boost pressure (or an equivalent size eg mass in the intake tract). In order to achieve the best possible control result (but at the same time to comply with the required for the application of the flatness-based control method reduction of the system) are preferably other sizes to consider: pressure losses in the air filter, the exhaust gas cooler, in the intercooler, in the catalyst and / or in the particulate filter. Temperatures or temperature changes in the exhaust gas cooler, in the intercooler and / or in the air collector.

By applying the flatness-based control method, it is now possible from a desired course of setpoints (here: boost pressure p _{ENG_IN} ' and fresh air mass M _{AIR_SOLL} ' ) the required actuating signals (control signal S _EGR for the exhaust gas recirculation device 8th and control signal S _VTG for the exhaust gas charger device 10 ) to calculate.

The inventive method, and thus the operation of the logic unit 12 , are described below by means of 2 explained. According to 2 includes a possible system for controlling the internal combustion engine 2 supplied gas mass M _{ENG_IN} (actual mass or composition of the gas mass) a first control loop RK1 for regulating the composition of the gas mass M _{ENG_IN} , and a second control loop RK2 for regulating the boost pressure p _{ENG_IN} (Where the control circuits interact with each other and combine to form a closed loop) and thus to control the actual gas mass and composition of the supplied gas stream.

The first control loop RK1 includes a regulator R1 for generating a controller manipulated variable S _R1 and a calculation model M1 for determining a pre-tax amount SW1 , The controller control variable S _R1 becomes dependent on a fresh air mass setpoint M _{AIR_soll} and a fresh air mass actual value M _HFM determined. Parallel to this is the calculation model M1 a pre-tax value SW1 depending on the over the exhaust gas recirculation device 8th recycled exhaust air mass M _EGR and in the exhaust tract 6 or in the exhaust gas recirculation channel of the exhaust gas recirculation device 8th (seen in the flow direction) in front of the exhaust gas recirculation valve 8a prevailing exhaust pressure p _{ENG_OUT} determined. As further input variable for the calculation of the pre-control value SW1 is with advantage still the exhaust gas temperature T _{ENG_OUT} in the exhaust tract 6 and / or the boost pressure p _{ENG_IN} in the intake tract 4 used. From the controller control variable S _R1 and the pilot tax quantity SW1 becomes a resulting manipulated variable S _EGR for controlling the exhaust gas recirculation device 8th educated.

The second control circuit RK2 includes another regulator R2 for generating a controller manipulated variable S _R2 and another calculation model M2 for determining a pre-tax amount SW2 , The controller control variable S _R2 is dependent on a boost pressure setpoint p _{ENG_IN_Soll '} and a boost pressure actual value p _{ENG_IN} determined. Parallel to this is the calculation model M2 a pre-tax value SW2 depending on the turbine 10a acting exhaust gas mass M _VTG and the predetermined exhaust pressure setpoint p _{ENG_OUT} determined. As further input variable for the calculation of the pre-control value SW2 is with advantage still the exhaust gas temperature T _{ENG_OUT} and / or the pressure p ₄₀ at the exit of the turbine 10a used. From the controller control variable S _R2 and the pilot tax quantity SW2 becomes a resulting manipulated variable S _VTG for controlling the exhaust gas charging device 10 educated.

Alternatively to the described embodiment, in which the manipulated variables S _EGR and S _VTG can be determined in each case from parallel determined controller control variable and pilot control variable, the determination of the pilot control variables can also be done by the controller control variable is not merged with the output value of the parallel calculation model, but rather is switched as an additional input to the input of the respective calculation model. The manipulated variable to be formed is then directly the output signal of the respective calculation model. This alternative method is illustrated by the dotted connection of the controller output to the respective input of the assigned calculation model.

In the present embodiment of the invention, the inputs to the controllers R1 . R2 as well as the input variables for the calculation models M1 . M2 determined by a calculation model for calculating setpoint curves.

This calculation model comprises a nominal value input SWV, via which, depending on a load signal (driver request) from characteristic maps and correction tables, nominal values for the fresh air mass M _{AIR_SOLL} and the boost pressure p _{ENG_IN_SOLL} be specified. As an alternative to these setpoints, there may be two other setpoints associated with the gas mass M _{ENG_IN_SOLL} M _{AIR_SOLL} or the boost pressure p _{ENG_IN_SOLL} be correlated to be specified (eg: boost pressure and exhaust gas recirculation rate or boost pressure and oxygen concentration in the air collector or boost pressure and oxygen concentration in the exhaust system or the like).

The setpoints of the setpoint input SWV become a setpoint shaping SWF where, if necessary, they are limited in their maximum values. The setpoint calculation determines physically possible setpoint value curves from the specified setpoint values. After a physical model is present, this can take into account boundary conditions (eg maximum supercharger speed, maximum exhaust back pressure (pressure p _{ENG_OUT} in the exhaust tract 6 ), ...) respectively. The maximum value limitation can be easily by simple filter elements (eg PT1 Filter).

The possibly limited or unlimited nominal values of fresh air mass M _{AIR_SOLL} 'and boost pressure p _{ENG_IN_SOLL} 'become a mathematical calculation model SGT (in the form of a manipulated variable transformation). In addition to the setpoint specifications, the manipulated variable transformation SGT via a model calculation MB other necessary variables such as pressure losses, pressure conditions and / or supplied total air mass (or total gas mass) provided. The model calculation determines these variables from actual values of the internal combustion engine (measured or calculated). The actual values to be considered here are in particular the following: boost pressure p _{ENG_IN} , supplied fresh air mass M _HFM , current engine speed, amount of fuel supplied M _B , Boost pressure p _{ENG_IN} (or pressure p ₂₀ after a possibly existing compressor) and temperature T _{ENG_IN} the supplied gas mass (or temperature T ₂₀ the air mass after a possibly existing intercooler) the compressed and cooled fresh air mass M _HFM ' , print p _{ENG_OUT} and temperature T _{ENG_OUT} the exhaust gas mass flow M _{ENG_OUT} (Sizes are measured or calculated). By means of the manipulated variable transformation SGT, the input variables already described above for the two controllers R1 . R2 and the two calculation models M1 . M2 to calculate the pilot control values. About the manipulated variable transformation SGT are from the setpoint curves of fresh air mass M _{AIR_SOLL} ' and boost pressure p _{ENG_IN_SOLL} 'using the flatness-based control method setpoint curves for the exhaust gas recirculation flow M _EGR and the turbine 10a acting exhaust gas flow M _VTG and a setpoint curve for the exhaust tract 6 prevailing exhaust pressure p _{ENG_OUT} generated.

Claims (3)

Method for controlling an internal combustion engine of a motor vehicle, wherein the internal combustion engine (2) has an intake tract (4) on the inlet side and an exhaust tract (6) on the outlet side, and a controllable exhaust gas turbocharger device (10) with a compressor (10b) in the intake tract (4) and a turbine (10a) in the exhaust gas tract (6) and a controllable exhaust gas recirculation device (8) for controlling an exhaust gas recirculation flow (M _EGR ) are present, with the following method steps: - Determining a target exhaust gas recirculation flow (M _EGR ), the turbine (10 a) acting on target Exhaust gas flow (M _VTG ) and a desired exhaust gas pressure (P _{ENG_OUT} ) in the exhaust tract in dependence ◯ a desired fresh air mass (MAIR_SOLL) and a desired boost pressure (p _{ENG_IN_SOLL} ) or ◯ two with the desired fresh air mass (MAIR_SOLL) and the target _Boost pressure (p _{ENG_IN_SOLL} ) of correlating nominal quantities; depending on the desired exhaust gas recirculation flow (M _EGR ) and the target exhaust gas pressure (PENG_OUT), determining a first pilot control quantity (SW1) of a first control loop (RK1) using a first calculation model (M1), wherein the first control loop (RK1) has a first manipulated variable (S _EGR ) for controlling the exhaust gas recirculation device (8) generated; and - depending on the desired exhaust gas pressure (p _{ENG_OUT} ) and the desired exhaust gas flow (M _VTG ), determining a second pilot control variable (SW2) of a second control loop (RK2) using a second calculation model (M2), wherein the second control loop (RK2) a second manipulated variable (S _VTG ) for controlling the exhaust gas turbocharger device (10) generated. Method according to Claim 1 , wherein the first manipulated variable (S _EGR ) and the second manipulated variable (S _VTG ) in each case from a manipulated variable of a controller (R1, R2) of the first control loop (RK1) or second control loop (RK2) and the first pilot control variable (SW1) or second pilot control variable (SW2) are determined. Method according to Claim 1 , Wherein the respective manipulated variable of a regulator of the first control loop (RK1) or second control loop (RK2) is connected as an additional input variable to the input of the first calculation model (M1) or second calculation model (M2).

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