EP3763933B1 - Method for volumetric flow based pump-synchronous, in particular cylinder-selective rail pressure control for a fuel supply system of a combustion engine with current detection and current regulation of the actuators of the rail pressure control - Google Patents

Description

The invention relates to a method for regulating a rail pressure caused by a high-pressure pump in a fuel storage for a fuel supply system of an internal combustion engine, wherein a crank angle-related or cam angle-related fixed angle difference of the internal combustion engine between a top dead center position of a cylinder piston of a cylinder of the internal combustion engine and a top dead center position Position of the pump piston of the high-pressure pump of the fuel supply system is taken into account when metering the delivery volume of the high-pressure pump.

From the publication DE 10 2016 204 386 A1 a method for regulating a rail pressure caused by a high-pressure pump in a fuel rail for an internal combustion engine is already known, in which the rail pressure is regulated synchronously with an engine speed of the internal combustion engine of the high-pressure pump. The rail pressure is therefore not regulated in the known fixed, time-synchronous calculation grid, but rather in a time-variable, engine speed-synchronous calculation grid, the respective grid interval of which is preferably from one top dead center to the next, based on a single cylinder or all cylinders of the internal combustion engine extends. The high-pressure pump provides a quantity of fuel with each pump delivery stroke. However, the sequence of pump delivery strokes of the high-pressure pump does not follow the fixed scanning pattern of the rail pressure controller, but is determined by the current operating state of the internal combustion engine.

The known fuel supply system includes a rail pressure regulator for using the proposed method. A high-pressure pump is supplied with fuel from a tank by a pre-feed pump via a low-pressure line. The high-pressure pump pumps fuel into a fuel rail via a high-pressure line. The delivery volume of the high-pressure pump is set according to a delivery volume control value that a rail pressure regulator has calculated to regulate the rail pressure in the fuel rail. The rail pressure controller is composed of a PID controller and a pilot control unit. The PID controller is given a rail pressure control deviation supplied, which has been calculated as the difference between the rail pressure setpoint calculated synchronously with the engine speed and the actual rail pressure value detected synchronously with the engine speed with a rail pressure sensor, and calculates an additive correction volume flow synchronously with the engine speed. A calculation carried out synchronously with the engine speed means that this calculation is carried out once per top dead center of the internal combustion engine.

The pilot control unit is supplied with an injection quantity calculated synchronously with the engine speed and a desired pressure change value, so that the pilot control unit calculates a pilot control value synchronously with the engine speed. The sum of the additive correction volume flow and the pilot control value is fed to the high-pressure pump as a delivery volume control value in order to specify the delivery volume of the current delivery stroke and to set the rail pressure setpoint ps in the fuel rail.

The publication is supplemented DE 10 2006 026 928 A1 referred. It describes a method for operating an injection system of an internal combustion engine, which includes a combustion chamber, an injector for injecting fuel into the combustion chamber and a high-pressure fuel pump for generating a time-dependent injection pressure, with the steps: determining an injection quantity of fuel to be injected into the combustion chamber by the injector, Determining at least one injection time window for injecting the fuel, then calculating the time-dependent injection pressure present at the injector at the beginning of the injection time window, then determining at least one injection time interval from the at least one injection time window based on the calculated one at the injector at the beginning of the Injection time window, time-dependent injection pressure applied, so that at the end of the at least one injection time interval essentially the injection quantity has been injected, and then injecting the fuel in the at least one injection time interval.

Finally, the publication reveals DE 10 2016 211 128 A1 a further method for regulating a rail pressure caused by a high-pressure pump in a fuel rail for an internal combustion engine, wherein the rail pressure regulated by a regulator is adjusted by at least one adjusting device on the fuel rail side. The at least one fuel rail-side adjusting device is set based on a volume flow value determined by the controller.

The invention is based on the object of improving the rail pressure control.

The starting point of the invention is that in a classic time-synchronous rail pressure control that works in a 10ms sampling grid, depending on the engine speed, the engine-synchronous pump event is under-sampled or over-sampled. This disadvantageously leads to pressure oscillations in the form of beats and aliasing, which cannot be completely corrected even at stationary operating points.

The conventional rail pressure control should also be adapted to the task to suit the newly available high-pressure pumps, which can provide a volume flow for each work cycle.

The best possible control performance should be achieved with deviations between the setpoint and actual value of less than 2% of the current setpoint. Furthermore, computing time and code memory in the control unit should be saved, the calibration and validation effort should be reduced and easy adaptation to different pump designs, pressure control valve variants and high-pressure components should be made possible.

These effects have a particularly negative impact on modern high-pressure pumps, in which the delivery volume is influenced from one delivery stroke to the next over the entire adjustment range. So far, the only solution has been an extremely low circuit gain, which means that the classic time-synchronous rail pressure controller is far inferior to the method according to the invention explained below, especially in dynamic pressure change situations.

According to the previous statements, a method for regulating a rail pressure caused by a high-pressure pump in a fuel storage for a fuel supply system of an internal combustion engine is already known, wherein a crank angle-related or cam angle-related fixed angle difference of the internal combustion engine between a top dead center position of a cylinder piston of a cylinder of the internal combustion engine and a Top dead center position of the pump piston of the high-pressure pump of the fuel supply system is taken into account when metering the delivery volume of the high-pressure pump.

Starting from this starting point, it is provided that a recurring discretization of a control deviation of the rail pressure occurs in synchronism with the pump per segment, which corresponds to one revolution of a crankshaft and thus the movement of the pump piston of the high-pressure pump from the top dead center position of the pump piston to the next top dead center position in the fuel storage and based on the discrete control deviation, a volume-related discrete volume control difference, in particular cylinder-selective, is calculated.

It is further provided that the discrete control deviation is calculated as the difference between the discretized actual rail pressure and the discretized target rail pressure, in particular cylinder-selective, by combining discretized pressure information from a rail pressure sensor of the actively detected pump-synchronous segment with the discretized target rail pressure of the Working cycle of the preceding pump-synchronous segment is compared in order to determine the discrete, in particular cylinder-selective, control difference.

According to the invention, the method is characterized in that the volume-related discrete volume control difference is supplied as an input variable to a control module for the high-pressure pump and a control module for a pressure control valve assigned to the fuel storage, the discrete volume control difference being linked to a pilot control module, whereby the pump is synchronous and in particular the manipulated variables for the high-pressure pump and the pressure control valve are calculated in an output module in a cylinder-selective manner for each segment and are fed to the actuators of the high-pressure pump and the pressure control valve for volume-based and in particular cylinder-selective adjustment of the rail pressure.

In the non-cylinder-selective approach and the cylinder-selective approach, it is preferably provided that the manipulated variables of the actuators of the components for regulating the rail pressure in the fuel storage are supplied to an output module and are calculated in the output module for volume-based adjustment of the rail pressure, with current detection and Current control of the actuators is carried out on the basis of an observer model.

In the non-cylinder-selective approach, it is preferably provided that the volume-related discrete volume control difference is supplied as an input variable to a control module for the high-pressure pump and a control module for a pressure control valve assigned to the fuel storage, the discrete volume control difference being linked to a pilot control module, whereby The control variables for the high-pressure pump and the pressure control valve are calculated in an output module in an output module and fed to the actuators of the high-pressure pump and the pressure control valve for volume-based adjustment of the rail pressure.

The non-cylinder-selective approach also provides that the discrete control deviation is calculated as the difference between the discretized actual rail pressure and the discretized target rail pressure by combining discretized pressure information from a rail pressure sensor of the actively detected pump-synchronous segment with the discretized target rail pressure a working cycle of the previous pump-synchronous segment is compared to determine the discrete control difference.

In the other cylinder-selective approach that expands the basic concept, the volume-related discrete volume control difference is calculated cylinder-selective by supplying the volume-related discrete volume control difference as cylinder-selective input variables to a control module for the high-pressure pump and a control module for a pressure control valve assigned to the fuel storage, whereby the discrete volume -Control difference is linked to a pilot control module, whereby the manipulated variables for the high-pressure pump and the pressure control valve are calculated in an output module in a pump-synchronous and cylinder-selective manner for each segment and are fed to the actuators of the high-pressure pump and the pressure control valve for volume-based, cylinder-selective adjustment of the rail pressure.

In the cylinder-selective approach, it is preferably provided that the discrete control deviation is calculated cylinder-selective as the difference between the discretized actual rail pressure and the discretized target rail pressure by combining discretized pressure information from a rail pressure sensor of the actively detected pump-synchronous segment with the discretized target rail pressure, of the pump-synchronous segment preceding one working cycle is compared in order to determine the discrete cylinder-selective control difference, as is explained in detail in the description.

According to the invention, the target rail pressure is discretized at a time that is determined with a trigger start signal that is issued repeatedly at the beginning of a pump-synchronous segment. It is intended that the actual rail pressure is recorded and discretized repeatedly within the segment started by the trigger start signal.

• in dem Segment maximaler Ist-Raildruck und
• in dem Segment minimaler Ist-Raildruck und
• in dem Segment berechneter Mittelwert

diskretisiert und wahlweise mit dem diskretisierten Soll-Raildruck zur Bestimmung der diskreten, insbesondere zylinderselektiven Regelabweichung verglichen wird.It is preferably provided that the actual rail pressure, which is recorded repeatedly within the pump-synchronous segment, as

• in the segment maximum actual rail pressure and
• in the segment minimum actual rail pressure and
• Average calculated in the segment

discretized and optionally compared with the discretized target rail pressure to determine the discrete, in particular cylinder-selective, control deviation.

It is also preferred that for the control, in particular cylinder-selective control, the detected minimum discrete pressure or the detected maximum discrete pressure or the discrete mean value is used as the actual value for comparison with the discrete target rail pressure, depending on the system requirements when pressure builds up the maximum discrete pressure and, when the pressure is reduced, the minimum discrete pressure is used to reduce control oscillations, in particular cylinder-selective control oscillations, or to avoid overshoots or undershoots, in particular cylinder-selective overshoots or undershoots.

A special aspect of the invention further provides that the discrete control deviation is converted into the volume flow-based discrete volume control difference or volume flow-based discrete cylinder-selective volume control difference, with a permanent fuel leakage of the high-pressure system of the fuel supply system also being taken into account by addition.

berücksichtigt, insbesondere zylinderselektiv berücksichtigt wird.The pressure-based discretized control deviation Δp _Rail or pressure-based discretized cylinder-selective control deviation Δp _Rail is advantageously converted into a volume flow-based volume control difference ΔV _Rail or volume flow-based cylinder-selective volume control difference ΔV _Rail , the pressure- and temperature-dependent specific elasticity modulus E of the respective fuel being used during the conversion and the space volume V _H of the fuel high pressure system of the fuel supply system according to the conversion formula $$\Delta {\mathrm{v}}_{\mathrm{Rail}}=\frac{v_{\mathrm{H}}}{E\left(p,T\right)}\ast \Delta {\mathrm{p}}_{\mathrm{Rail}}$$

taken into account, in particular taken into account in a cylinder-selective manner.

1. a) die Kraftstoff-Einspritzmengen der Injektoren, insbesondere zylinderselektiv und
2. b) die Kraftstoff-Schaltleckagen der Injektoren, insbesondere zylinderselektiv und
3. c) ein Druckänderungswunsch bezüglich des Soll-Raildrucks des Kraftstoffspeichers, insbesondere zylinderselektiv berücksichtigt,
   wobei ferner
4. d) die Kraftstoff-Dauerleckage des Hochdrucksystems des Kraftstoffversorgungssystems durch eine pumpensynchrone segmentweise wiederkehrende separate Umrechnung mit einer Z-Transformation ermittelt und der volumenbezogenen diskreten Volumen-Regeldifferenz hinzugefügt wird, beziehungsweise bei zylinderselektiver Vorgehensweise, wird die Kraftstoff-Dauerleckage den volumenbezogenen diskreten zylinderselektiven Volumen-Regeldifferenzen anteilig hinzugefügt.

During the pump-synchronous, segment-wise recurring conversion of the pressure-based discrete control deviation, in particular cylinder-selective control deviation, into the volume-related discrete volume control difference, in particular cylinder-selective volume control difference,

1. a) the fuel injection quantities of the injectors, in particular cylinder-selective and
2. b) the fuel switching leaks of the injectors, especially cylinder-selective and
3. c) a pressure change request with regard to the target rail pressure of the fuel storage, in particular taken into account in a cylinder-selective manner,
   whereby further
4. d) the permanent fuel leakage of the high-pressure system of the fuel supply system is determined by a pump-synchronous, segment-wise recurring, separate conversion with a Z transformation and is added to the volume-related discrete volume control difference, or in the case of a cylinder-selective approach, the permanent fuel leakage is the volume-related discrete cylinder-selective volume control differences added proportionately.

Specific cylinder-selective approach:

According to the invention, it is provided that the injectors receive the same quantity setpoints from cylinder to cylinder in stationary operation, which are compared cylinder-selective with the quantity decreases from the rail, with injection quantity errors being determined cylinder-selectively, which are assigned to the injectors, with a type of quantity deviations being determined Error groups are assigned. The injection quantity errors are advantageously grouped depending on the cause, in particular depending on the level of the injection quantity error resulting from the target/actual comparison, the injectors being in operation in an error group with an injector defect, an error group with an aging-related injector drift or an error group with a changing Switching leakage quantity are assigned, the injection quantity errors being determined within the cylinder-selective control in the controller and advantageously corrected in the injection system and/or leading to a replacement of the respective injector(s).

A correction in the injection system can be made in various ways. In a preferred embodiment, the correction takes place by changing the injector activation duration.

The non-cylinder-selective fuel supply system (basic concept) and the cylinder-selective fuel supply system (extension of the basic concept) differ in terms of the building blocks, as will become clear below.

• einen Sollwertvorgabe-Baustein des Raildrucks und eine zugehörigen Sollwert-Diskretisierungs-Baustein und
• einen Istwert-Signalerfassungs-Baustein des Raildrucks und einen Istwert-Diskretisierungs-Baustein,
• sowie einen Regelfehler-Berechnungs-Baustein und
• einen Umrechnungs-Baustein umfasst, der aus einer druckbasierten diskretisieren Regeldifferenz eine Umrechnung in eine volumenstrombasierte Regeldifferenz vornimmt,
• wobei der Umrechnungs-Baustein mit einer Regler-Zustandsmaschine verknüpft ist, welche die diskrete Eingangsgröße für den Regler-Baustein der Hochdruckpumpe und die diskreten Eingangsgröße für den Regler-Baustein des Druckregelventils ausgibt,
• wobei die Regler-Bausteine mit einem Vorsteuer-Baustein verknüpft sind, wodurch mittels des Vorsteuer-Bausteins und der aufgeschalteten Regler-Bausteine pumpensynchron je Segment die Stellgrößen für die Hochdruckpumpe und das Druckregelventil einem Ausgabe-Baustein zugeführt und berechnet werden, und den Stellgliedern der Hochdruckpumpe und des Druckregelventils zur volumenbasierten Einstellung des Raildrucks zugeführt werden.

The fuel supply system associated with the method is set up to carry out the method, the fuel supply system in the basic concept (without cylinder-selective rail pressure control) being used to determine a discrete input variable for a controller module for the high-pressure pump and to determine a discrete input variable for a regulator module for a pressure control valve assigned to the fuel storage comprising the following further modules,

• a setpoint specification module for the rail pressure and an associated setpoint discretization module and
• an actual value signal acquisition module for the rail pressure and an actual value discretization module,
• as well as a control error calculation module and
• comprises a conversion module that converts a pressure-based discretized control difference into a volume flow-based control difference,
• wherein the conversion module is linked to a controller state machine, which outputs the discrete input variable for the controller module of the high-pressure pump and the discrete input variable for the controller module of the pressure control valve,
• whereby the controller modules are linked to a pilot control module, whereby the control variables for the high-pressure pump and the pressure control valve are fed and calculated to an output module and calculated in pump synchronization per segment by means of the pilot control module and the connected controller modules, and to the actuators of the high-pressure pump and the pressure control valve for volume-based adjustment of the rail pressure.

• einen Sollwertvorgabe-Baustein des Raildrucks und eine zugehörigen Sollwert-Diskretisierungs-Baustein und
• einen Istwert-Signalerfassungs-Baustein des Raildruck und einen Istwert-Diskretisierungs-Baustein,
• sowie einen Regelfehler-Berechnungs-Baustein und
• einen Umrechnungs-Baustein umfasst, der aus einer druckbasierten diskretisieren zylinderselektiven Regeldifferenz eine Umrechnung in eine volumenstrombasierte zylinderselektive Regeldifferenz vornimmt,
• wobei der Umrechnungs-Baustein mit einer Regler-Zustandsmaschine verknüpft ist, welche zylinderselektiv die diskrete Eingangsgröße dem jeweiligen Regler-Baustein der Hochdruckpumpe und zylinderselektiv die diskreten Eingangsgröße dem jeweiligen Regler-Baustein des Druckregelventils ausgibt,
• wobei die Regler-Bausteine jeweils zylinderselektiv mit einem Vorsteuer-Baustein verknüpft sind, wodurch mittels des Vorsteuer-Bausteins und der aufgeschalteten zylinderselektiven Regler-Bausteine pumpensynchron je Segment die Stellgrößen für die Hochdruckpumpe und das Druckregelventil einem Ausgabe-Baustein zugeführt und berechnet werden, und den Stellgliedern der Hochdruckpumpe und des Druckregelventils zur volumenbasierten zylinderselektiven Einstellung des Raildrucks zugeführt werden.

The fuel supply system associated with the method is expanded from the basic concept, namely with cylinder-selective rail pressure control for carrying out the method, with the fuel supply system having several cylinder-selective regulator modules for the high-pressure pump to determine the respective discrete input variable of the respective cylinder and to determine a discrete input variable of the respective cylinder, a plurality of regulator modules for a pressure control valve assigned to the fuel storage cylinder, comprising the following further modules,

• a setpoint specification module for the rail pressure and an associated setpoint discretization module and
• an actual value signal acquisition module for the rail pressure and an actual value discretization module,
• as well as a control error calculation module and
• comprises a conversion module which converts a pressure-based discretized cylinder-selective control difference into a volume flow-based cylinder-selective control difference,
• whereby the conversion module is linked to a controller state machine, which selectively assigns the discrete input variable to the respective controller module High-pressure pump and cylinder-selective outputs the discrete input variable to the respective controller module of the pressure control valve,
• wherein the controller modules are each linked to a pilot control module in a cylinder-selective manner, whereby the manipulated variables for the high-pressure pump and the pressure control valve are fed and calculated to an output module in a pump-synchronous manner per segment using the pilot control module and the connected cylinder-selective controller modules, and the Actuators of the high-pressure pump and the pressure control valve are supplied for volume-based, cylinder-selective adjustment of the rail pressure.

Yet another aspect of the invention is that the fuel supply system includes an observer module that observes a signal processing chain for current detection and current control of the actuators of the fuel supply system, as is also detailed in the description.

The internal combustion engine is advantageously operated with any liquid fuel or fuel mixture, whereby the linearization of the conversion of pressure difference into volume flow difference can be advantageously adapted to the respective fuel by means of a physically different elasticity modulus. As a result, the method explained and the design of the fuel supply system can be applied and used not only for diesel engines, which are designed in particular as common-rail diesel engines, but also for gasoline engines that use a gasoline engine - spark-ignited - combustion process.

Figur 1

eine schematische Darstellung eines Kraftstoffversorgungssystems, das mit einer volumenstrombasierten pumpensynchronen Regelstruktur, insbesondere volumenstrombasierten pumpensynchronen und zylinderselektiven Regelstruktur zur Raildruckregelung gemäß dem erfindungsgemäßen Verfahren betrieben wird;

Figur 2A

die volumenstrombasierte pumpensynchrone Regelstruktur zur Raildruckregelung, die in einem elektronischen Steuergerät mit einem Mikroprozessor abgelegt und zur Ausführung des erfindungsgemäßen Verfahrens eingerichtet ist;

Figur 2B

die volumenstrombasierte pumpensynchrone und zylinderselektive Regelstruktur zur Raildruckregelung, die in einem elektronischen Steuergerät mit einem Mikroprozessor abgelegt und zur Ausführung des erfindungsgemäßen Verfahrens eingerichtet ist;

Figur 3

die erfindungsgemäße volumenstrombasierte pumpensynchrone Regelstruktur zur Raildruckregelung gemäß Figur 2A oder die erfindungsgemäße volumenstrombasierte pumpensynchrone und zylinderselektive Regelstruktur zur Raildruckregelung gemäß Figur 2B mit Stromerfassung und Stromregelung der Stellglieder der Raildruckregelung weiter erfindungsgemäß auf der Basis eines Beobachter-Modells.

The invention is explained below with reference to the associated drawings. Show it:

Figure 1

a schematic representation of a fuel supply system that is operated with a volume flow-based pump-synchronous control structure, in particular volume flow-based pump-synchronous and cylinder-selective control structure for rail pressure control according to the method according to the invention;

Figure 2A

the volume flow-based pump-synchronous control structure for rail pressure control, which is stored in an electronic control device with a microprocessor and is set up to carry out the method according to the invention;

Figure 2B

the volume flow-based pump-synchronous and cylinder-selective control structure for rail pressure control, which is stored in an electronic control device with a microprocessor and is set up to carry out the method according to the invention;

Figure 3

the volume flow-based pump-synchronous control structure for rail pressure control according to the invention Figure 2A or the volume flow-based pump-synchronous and cylinder-selective control structure according to the invention for rail pressure control Figure 2B with current detection and current control of the actuators of the rail pressure control further according to the invention on the basis of an observer model.

The Figure 1 shows a fuel supply system 100, which has a volume flow-based pump-synchronous, in particular cylinder-selective rail pressure control according to Figure 2A and 2 B is operated.

A high-pressure pump 1 is supplied with fuel from a fuel tank 3 by a pre-feed pump 2 via a low-pressure line 2.1. A filter unit 5 and a duo sensor 6, which measures pressure p6 and temperature T6 in front of the high-pressure pump 1 in the low-pressure line 2.1, are arranged in the low-pressure line 2.1.

The high-pressure pump 1 pumps fuel into a fuel reservoir, in particular into a fuel rail 4, via a high-pressure line 1.4. The fuel rail 4 includes a rail pressure sensor 7, which detects the rail pressure p7 in the fuel rail 4.

The fuel rail 4 further comprises a pressure control valve 8, which within the method controls a predeterminable volume flow V8 from the fuel rail 4 via a return line 8.2.1 into the low-pressure line 2.1.

Between the fuel rail 4 and the injectors 9n; (n = 1, 2, 3...) 91, 92, 93, 94 show the injector lines 4.9, via which the injectors 9n are supplied with fuel.

The injectors 9n have leakage lines which open into a common return line 9.3. The return line 9.3 opens into a high-pressure pump return line 1.3 of the high-pressure pump 1, which leads back to the fuel tank 3.

A control unit S1, in particular an engine control unit, is connected via control lines (without reference numbers) directly to the duo sensor 6, the high-pressure pump 1, the pressure control valve 8, the rail pressure sensor 7 and the injectors 91, 92, 93, 94 and, in the exemplary embodiment, indirectly via a control unit S2 is connected to the pre-feed pump 2, which is designed as a low-pressure pump.

The Figure 2A shows the volume flow-based pump-synchronous control structure for rail pressure control in the basic concept, which is stored in an electronic control device, in particular the control device S1, which is set up to carry out one of the methods presented above. The control device S1 and the control device S2 are operated via a computer program to carry out the method, a machine-readable storage medium with the computer program recorded thereon being provided on the computer.

The volume flow-based pump-synchronous control structure for rail pressure control is based on the Figure 2A explained in detail below.

The basic idea of the method explained below for future diesel engines, which are designed as common rail diesel engines, is that a required rail pressure of up to 2700 bar is generated with the high-pressure pump 1 by a predeterminable volume flow in the rail 4.

With a positive mass balance, i.e. increasing volume flow in Rail 4, the pressure in Rail 4 increases. The rail pressure sensor 7 provides the control circuit consisting of a pilot control model, a controller and an actuator of the high-pressure pump 1 with the corresponding pressure information.

According to the invention, the input variable of the method for operating the fuel supply system 100 according to the invention is a certain volume flow, which is supplied to the high-pressure pump 1 or discharged through the pressure control valve 8.

The object of the invention is therefore that the complete high-pressure control, i.e. the rail pressure high-pressure control within the rail 4 of the fuel supply system 100, from a time-based cyclical calculation of a rail pressure controller for regulating the rail pressure in the rail 4 to a volume flow-based and pump-synchronous one based on the engine segment of the internal combustion engine discrete calculation for rail pressure control (in a two-position concept (pressure control valve control and high-pressure pump control).

For this purpose, according to the invention, it is necessary to discretely describe the volume flows to be taken into account and the associated model of the control structure according to the invention.

For this purpose, the pressure information p7 _Act from the rail pressure sensor 7 of a motor-synchronous/pump-synchronous segment is compared with the target rail pressure p7 _target of the previous motor-synchronous/pump-synchronous segment (this is referred to as the delayed target rail pressure) in order to determine the discrete control deviation Δp7.

This pressure difference Δp7 is converted into a volume difference via the elastic modulus E of the fuel and via the fuel temperature T6 determined by the duo sensor 6 and processed as an input variable ΔV _Rail in a controlled system.

This volume difference ΔV _Rail is supplied as an input variable to the controlled system using the digital metering unit (not shown), which is preferably arranged in the pump room of the high-pressure pump 1 or by controlling the pressure control valve 8, and the actuators of the high-pressure pump 1 or the pressure control valve 8 are controlled, with the discretization , that is, the calculation of the volume difference ΔV _Rail can be varied synchronously with the pump for each motor segment.

For this purpose, a volume balance is created that physically describes the pressure _p7 Actual in Rail 4.

The volume balance of the volume flow-based segment-synchronous calculation assumes a constant volume V _H of the high-pressure system, in which, depending on the pressure, there is a certain volume of fuel, which is basically supplied via the high-pressure pump 1 and discharged via the pressure control valve 1.

The volume V _H of the high-pressure system of the fuel supply system 100 includes the volume of the rail 4, the volume of the injector lines 4.9 to the injectors 9n, the volume of space in the injectors 9n up to the throttle point within the injectors 9n, the supply line 1.4 of the high-pressure pump 1 to the rail 4 the check valve in the supply line 4.9 and the dead volume of the high-pressure pump 1 (dead volume = volume of space between TDC of the piston of the high-pressure pump 1 and the check valve in the supply line to the rail 4).

1. a) aus den Kraftstoff-Einspritzmengen V_9n über die Injektoren 91, 92, 93, 94 und
2. b) den Kraftstoff-Schaltleckagen V_SLeck der Injektoren 91, 92, 93, 94 sowie der
3. c) der Kraftstoff-Dauerleckage V_DLeck des Hochdrucksystems des Kraftstoffversorgungssystems 100

zusammensetzt.Starting from the spatial volume V _H of the high-pressure system of the fuel supply system 100, a total volume V _Ges-Ab is removed from the high-pressure system in a segment-synchronous manner, which is a total of

1. a) from the fuel injection quantities V _9n via the injectors 91, 92, 93, 94 and
2. b) the fuel switching leaks V _SLeak of the injectors 91, 92, 93, 94 and the
3. c) the permanent fuel leak V _DLeak of the high pressure system of the fuel supply system 100

composed.

The volumes a) and b) are taken event-related, while c) the permanent fuel leakage _VDLeck of the high-pressure system is discretized via a Z-transformation. This means that the non-event-related permanent leak V _DLeck of the high-pressure system is converted into an event-related, segment-synchronous discrete volume. In other words, an event-related discretization of the permanent leakage V _DLeck of the high-pressure system takes place, so that the volumes a), b), c) can be added accordingly as the total volume V _Ges-Ab taken from the high-pressure system.

Added to this is d) the so-called load and/or speed-dependent change request in the rail pressure, the so-called pressure change request (also referred to as dynamic volume flow component) within the rail 4, which is achieved by supplying fuel volume (pressure increase) via the high-pressure pump 1 as a V _{Δp rail specification} or by discharging fuel volume (pressure reduction) via the pressure control valve 8 within the volume balance as V _{Δp rail specification} .

• bei einer Druckerhöhung ein segmentsynchrones Volumen V_Zu zu dem Gesamt-Volumen V_Ges-Ab addiert oder
• bei einer Druckabsenkung wird ein segmentsynchrones Volumen V_Ges-Ab von dem Gesamt-Volumen V_Ges-Ab subtrahiert

Depending on whether the pressure change request concerns an increase or decrease in pressure

• When the pressure increases, a segment-synchronous volume V _Zu is added to the total volume V _Total-Ab or
• When the pressure drops, a segment-synchronous volume V _Ges-Ab is subtracted from the total volume V _Ges-Ab

The high-pressure pump 1 has, in a known manner and advantageously, a fixed assignment of the pump TDC in a segment-synchronous/cylinder-synchronous manner every 180° crank angle of the internal combustion engine to the cylinder piston TDCs of the cylinder pistons (not shown) of the internal combustion engine, whereby the engine speed corresponds to the high-pressure pump speed matches. There may be a certain fixed offset between the pump TDC and the cylinder piston TDC, but this is known and can be taken into account accordingly in the fixed assignment.

This fixed assignment makes it possible to base and discretize the volume flow-based and pump-synchronous discrete calculation for rail pressure control on this synchronicity. This means that only a discrete subset is obtained from a continuous amount of data or information, which simplifies the calculation of the variables within the controlled system.

The calculation according to the invention is carried out via a trigger start signal nsync (see Figures 2A and 2 B and Figure 3 ), whereby the calculation is carried out segment-synchronously/cylinder-synchronously every 180° crank angle, whereby the calculation of the variables of the controlled system is carried out separately for each of the cylinders or the associated injectors 9n, which inject into this cylinder.

According to the Figure 2A The volume flow-based pump-synchronous control structure for rail pressure control of the high-pressure pump 1 includes a signal detection module B1 for signal detection of the rail pressure p7 by means of the rail pressure sensor 7.

According to the invention, the detection of the rail pressure p7 takes place time-synchronously within the module B1 for the signal detection of the rail pressure p7 in a measuring grid in ms steps, with an actual value discretely segment-synchronously within the segment within the module B2, which is referred to as the actual value discretization module p7 Actual _is recorded and saved as the minimum pressure p _7Actual-min and as the maximum pressure p _7Actual-max , with these pressures p _7Actual-min , p _7Actual-max and also as the actual value p7 _Actual an average value p7 _Actual-50% of Press p _7Act-min , p _7Act-max is calculated within the segment and also saved.

According to the Figure 2A The volume flow-based pump-synchronous control structure for rail pressure control of the high-pressure pump 1 includes a setpoint specification module A1 for the setpoint specification of the rail pressure p7 _target , which is stored in the form of map data in the computer program of the engine control unit, which arises from the respective combustion process used and is predetermined.

According to the invention, this target rail pressure p7 _target is also discretized from any current specified time grid, that is, a conversion is carried out from the Time "slices" into the segment "slices", at the time nsync dem (trigger start signal), i.e. at the start of the calculation.

This explicitly means that the first value present in the segment disk is “frozen” within the time grid as the target rail pressure p7 _target and is therefore discretized. This discretization takes place in the setpoint discretization module A2.

Because the target rail pressure p7 _target at time nsync is "frozen" with the start of a time slice of the segment, the target rail pressure p7 _target desired from the previous segment (end of the previous segment = start of the next segment at time nsync) is discretized before, and is discretized and compared with the pressure information p7 _Ist from the rail pressure sensor 7 from the current, i.e. the subsequent segment within a work cycle, whereby a discrete control deviation Δp7 can be determined per segment (segment-synchronous). This procedure is necessary because the system always has a time delay. The control value of a pilot control generates an increase in the volume flow into the rail after the pump has delivered. Therefore, the target value p7 target used to form the difference _is delayed by exactly one working cycle and compared with the actual value p7 _actual of the following working cycle.

As explained above, the minimum pressure p _7min or the maximum jerk p _7max or the mean value p7 _{50% is} available as a discrete actual value p7.

Advantageously, within the control there is the possibility (selection of several discrete signals from the setpoint discretization module A2) for the control as the actual value _p7Is the minimum discrete pressure _p7Ist-min or the maximum discrete pressure _p7Ist-max or to use the discrete mean value p7 _actual-50% to compare the selected value with the discrete target rail pressure P7 _target , whereby, depending on the system requirements, the value p7 _actual-max is used when the pressure builds up and the value p7 _{actual-min is used when the pressure is} reduced is used to reduce control oscillations or to avoid overshoots or undershoots.

The corresponding pressure-related calculation is carried out in the control error calculation module A2/B2 (see Figure 2A ) into which the discretized target rail pressure values p7 _target and the discretized actual rail pressure values p7 actual _are received and compared segment-synchronously and calculated as a control error and saved.

At this point in the control error calculation, according to the invention, the pressure-based discretized control deviation Δp7 = Δp _Rail is converted into a volume flow-based control difference ΔV _Rail in a conversion module A2', B2', i.e. a volume flow difference by solving a differential equation, where E is pressure- and temperature-dependent specific modulus of elasticity of the respective fuel and V _H , as explained above, are the volume of the high-pressure fuel system of the fuel supply system 100. $$\Delta {\mathrm{v}}_{\mathrm{Rail}}=\frac{v_{\mathrm{H}}}{E\left(p,T\right)}\ast \Delta {\mathrm{p}}_{\mathrm{Rail}}$$

This conversion into the segment-synchronous volume error ΔV _Rail has the advantage that the non-linear fuel properties of the fuel are taken into account in the control.

The nonlinear properties of the fuel in terms of pressure, temperature and compressibility are not represented in pressure-based systems, which is a significant advantage of the present method, since these nonlinearities are taken into account by converting them into the segment-synchronous volume error ΔV _Rail .

This enables precise control and regulation with minimal control errors even in highly dynamic driving situations, which results in decisive advantages in terms of combustion stability and emissions.

As an interim summary, compared to the prior art there is a change in the recording of the variables through the segmentation in the blocks A1, B1 and the discretization in the blocks A2, B2 and a conversion from pressure-based variables to volume flow-based variables in the blocks A2/B2 as well A2'/B2'.

Due to the features of the basic concept described, a discrete volume control difference ΔV _Rail is available as an input variable for a controller module C, C1, C8, which is used directly for the volume flow-based actuators E1, E8 (high-pressure pump 1 and pressure control valve 8).

The expansion of the basic concept, the "cylinder selective control", will be discussed in more detail below under the same subheading.

The controller module C, C1, C8 includes as a sub-module a controller state machine C, which, depending on the requirements, adjusts the pressure based on volume flow/volume flow, i.e. depending on the discrete volume control difference ΔV determined in the conversion module A2`/B2` _Rail increases or decreases, and this decides whether control intervention via a PID controller module C1 of the high-pressure pump 1 (see Figure 2A ) “pressure increasing” or “pressure reducing” via a PID controller module C8 of the pressure control valve 8.

The structure also includes: Figure 2A a pilot control volume flow value module D as a fault controller for the segment-synchronous volume flow-based pilot control (command variable with disturbance variable compensation) of the fuel supply system, the command variable of which is combined with the PID controller module C1 of the high-pressure pump 1 and the PID controller module C8 of the pressure control valve 8, so that The PID controller modules C1, C8 only have to compensate for the control fluctuations of the fuel supply system.

The pre-control volume flow value module D receives the segment-synchronous volume flows mentioned under a) to d) in addition as pre-control variables, so that control of the controlled system is already guaranteed in the pre-control volume flow value module D.

The values of the fault controller of the pilot control volume flow value block D, which are controlled by the PID controller blocks C1, C8, are (compare Figure 2 ) is fed to an output module E, which electrically controls the actuators E1 and E8 of the high-pressure pump 1 and the pressure control valve 8 and adjusts the actuators E1 and E8 as required via the control system in a pump-segment-synchronous, volume-based manner.

“Cylinder selective control” extension:

According to the invention, the rail pressure control previously explained with regard to the basic concept is expanded to a so-called "cylinder selective control", as described below with reference to Figure 2B is explained.

For this purpose, for each cylinder, n = number of cylinders or the associated injectors 9n (compare Figure 1 ) a separate cylinder-selective control deviation ΔV _Rail , in particular a proportional component and / or an integrator component and / or a differential component, is calculated and according to the cylinder-selective control deviation ΔV _Rail , the control values E1, E8 are cylinder for cylinder and injector for injector 9n respectively Injection event for Injection event is selected segment-synchronously and, as explained above, is output based on volume flow for the high-pressure pump 1 or the pressure control valve 8.

Since the injectors 9n receive the same quantity setpoints from cylinder to cylinder in stationary operation, but different quantity decreases V _9n result from the rail 4 due to injector scattering, according to the invention, for example, the individual integrator shares of the cylinder-selective controllers C1 _n , C8 _n show the quantity deviations between the injectors 9 _n , which can have various causes. Depending on the type of quantity deviations, the causes can most likely be assigned to specific error groups.

According to Figure 2A In the basic concept according to the invention, a discrete volume control difference ΔV _Rail is available as an input variable for a controller module C, C1, C8, which is used directly for the volume flow-based actuators E1, E8 (high-pressure pump 1 and pressure control valve 8), whereby segment-synchronously for Each cylinder or injector 9n “only one” control structure is used repeatedly. An extension, the so-called "cylinder-selective control" in which several control structures are cylinder-selective (compare Figure 2B ) are used, is explained in more detail below.

Analogous to the basic concept, a segment-synchronous discrete volume control difference ΔV _Rail is available as an input variable for several (n) controller modules C1n, C8n, which, according to the "cylinder-selective" extension, is available directly for the volume flow-based actuators E1, E8 (high-pressure pump 1 and pressure control valve 8 ) is used.

For each cylinder or injector 9n there are several controller blocks C1n (in the exemplary embodiment n = 4; C11, C12, C13, C14), C8n (in the exemplary embodiment n = 4; C81) as sub-blocks that are assigned to a controller state machine C , C82, C83, C84) are available, which increase or decrease the pressure based on volume flow/volume flow depending on the segment requirements, i.e. depending on the discrete volume control difference ΔV _Rail determined in the conversion module A2`/B2`, whereby the controller State machine C decides whether the control interventions are segment-synchronous via several PID controller modules C1n of the high-pressure pump 1 (see Figure 2B ) “pressure increasing” or via several PID controller modules C8n of the pressure control valve 8 “pressure decreasing” should be done in a cylinder-selective manner.

The structure also includes: Figure 2B a pilot control volume flow value module D as a fault controller for the segment-synchronous volume flow-based pilot control (command variable with disturbance variable compensation) of the fuel supply system 100, the command variable of which is combined with the PID controller modules C1n of the high-pressure pump 1 and the PID controller modules C8n of the pressure control valve 8, so that the PID controller modules C1n, C8n only have to compensate for the control fluctuations of the fuel supply system.

This results in the following effects:

The high pressure control can now be carried out cylinder-selectively through the cylinder-selective control - in an extension of the basic concept - that is, for each cylinder or each injection process, an adapted, cylinder-selectively corrected manipulated variable is output as actuator output E1 of the high-pressure pump 1 or actuator output E8 of the pressure control valve 8.

In other words, the respective PID controller modules C1n, C8n can each be calibrated separately. The evaluation of the four individual PID controller modules C1n or C8n in the exemplary embodiment, that is to say the comparison of the different integrator shares and proportional shares in stationary operation, for example, advantageously allows for a cylinder-related or injector-related error analysis and cause classification, on the one hand A simple diagnostic function (on-board diagnosis without removal) or a diagnostic function (on-board diagnosis without removal) with a correction function is provided.

For example, a specific cylinder-related or injector-related error can be permitted via the diagnostic function up to a predeterminable threshold value and only after the threshold value is exceeded is a cylinder-related or injector-related error correction carried out.

According to the invention, there is in particular the possibility of grouping the injection quantity errors depending on the cause, with the injectors 9n, for example, during operation of an error group with an injector defect (on-board diagnosis of an injector defect without removal), or another error group with an aging-related injector drift (on-board diagnosis of the injector drift without removal). ) or another error group with a changing switching leakage quantity V _SLeck (on-board diagnosis of too high a switching leakage without removal), the injection quantity errors being advantageously within the On-board diagnosis can be called up to replace the defective injector 9n or can be taken into account and corrected within the cylinder-selective control.

In addition, the cylinder-selective control information, that is, the individual injection quantity errors of the individual injectors 9n, can generally be adapted and used to improve the pilot control D of the injectors 9n.

The respective cylinder-selective controlled variable C1n, C8n can also be advantageously converted into another reference variable, in particular considering the internal engine torque of the respective cylinders, so that by supporting the cylinder-selective rail pressure control, a cylinder-selective torque-dependent control is made possible, in which the cylinder-selective control information in particular can be used for cylinder torque equalization by, for example, passing a corresponding pilot control value from the cylinder-selective rail pressure control to a cylinder-selective torque controller.

Extension "Current detection and current control of the actuators":

A further aspect of the invention is that the high-pressure control in the described non-cylinder-selective control or in the described cylinder-selective control outputs an adapted corrected manipulated variable in an actuator output E1 of the high-pressure pump 1 or in an actuator output E8 of the pressure control valve 8.

In order to be able to fully utilize the advantages according to the invention of the non-cylinder-selective control or the described cylinder-selective control without system weakness in the area of current detection and current control of the pressure control valve 8 and the high-pressure pump 1, a method for improved current control using an observer model for rail pressure control is presented below a pressure control valve 8 and / or a high pressure pump 1 explained.

Up to now, current control of components, especially high-pressure components in the automotive industry, has been implemented using pulse width modulation (PWM) of a fast switch in the engine control unit. The PWM modulation creates an average current in the actuator, which is measured for current control with an analog to digital converter (AD converter) and then made available to a controller as the actual size. Due to the PWM modulation, the measured current contains frequencies/oscillations that are multiples of the PWM basic frequency are equivalent to. In order to be able to record the current without errors, there are two established methods.

A distinction is made between “PWM-synchronous current detection systems” and “time-synchronous current detection systems”.

PWM-synchronous current measurement systems, in which a hardware filter with a high cut-off frequency is used to eliminate high-frequency interference, have the following disadvantages: No average value-free measurement can be carried out. A sampling is carried out that lies in the frequency range of the HW filter with a high CPU load because the sampling frequency is coupled to the PWM basic frequency. With small PWM duty cycles, undersampling can occur due to alias errors, which leads to a center shift. The procedure is therefore rarely used.

Time-synchronous current detection systems, in which a HW filter with a low cutoff frequency is used to smooth the PWM oscillation on the current signal, have the following disadvantages: Due to the low cutoff frequency and high filter time constant, these HW filters have a high phase shift. The controller must be adapted to a relatively slow HW filter. The time-synchronous current detection systems also have poor control behavior in the event of faults because the actual value reaches the controller with a delay due to the slow HW filtering.

In general, current detection systems use a measuring resistor to use the voltage drop across the measuring resistor to determine the current in the actuator. This value is recorded cyclically using an AD converter and provided to the current control as an actual value. This current measurement value is regulated in a closed control loop. For sampling, this measured value must be filtered in front of the analog/digital converter using an analog hardware (HW) low-pass filter with a correspondingly defined cutoff frequency (usually between 10Hz and 50Hz for time-synchronous current measurement). This filter is usually an RC element. This creates a signal delay and a phase response that is a major disadvantage for the control loop, which is why the (internal) current controls are designed to be relatively slow.

As before, it should be noted that in the specific “rail pressure control” application here, the inner control loops in a rail pressure control controller cascade (control circuits of the current controllers) must generally be designed faster than the external control circuits (control circuits based on rail pressure) in order to achieve temporal decoupling.

The actuators for the actuator output E1, E8 of the high-pressure pump 1 and the pressure control valve 8 of the high-pressure control are the inner control circuits, with the actual hydraulic pressure control already explained (compare the components of the hydraulic pressure control in the Figures 2A and 2 B and the associated description) represent the external control loops.

After all this, it becomes clear that there is potential for improvement in the current detection and the current control of the pressure control valve 8 and the high-pressure pump 1 based thereon, with an improved procedure being explained below.

The solution according to the invention consists in a modified signal processing or signal processing chain, which according to the invention is an in Figure 3 Observer model shown includes.

In other words, an observer component W, called observer for short, is integrated into the signal processing chain and is advantageously used in the signal processing chain to control components 1 and 8.

This observer W, integrated into the signal processing chain, improves the current detection of the high-pressure pump 1 and the pressure control valve 8 and their current control in the described non-cylinder-selective rail pressure control and in the cylinder-selective rail pressure control equally.

The current detection is improved using the observer model in such a way that the delay times and phase shifts in the current detection, which arise from the analog filtering (HW filter) of the signal, are avoided, with the model ensuring that the observer W is constantly tracked , in which a so-called observation error converges to zero, where the observation error is defined as the difference between the measured value and the observed value.

The system according to the invention for current detection is in Figure 3 arranged in the output module component E and in Figure 3 illustrated in a schematically illustrated system diagram extracted from the output module component E.

The current detection system according to the invention is based on a time-synchronous current detection and a so-called state reconstruction or state vector construction.

The system diagram extracted from output module component E illustrates a voltage value u (which corresponds to a pulsating coil current or a pulsating coil voltage of a conventional PWM-synchronous current detection), which represents the input variable of the system for current detection.

der Steuereinheit der anzusteuernden Komponenten 1, 8 zugeführt wird.The voltage u represents the input variable of the coil $\frac{1}{\mathit{Ls}+R}$

the control unit of the components 1, 8 to be controlled is supplied.

ist ein Stromwert i₁, der als sogenannter Effektivwert der Spule $\frac{1}{\mathit{Ls}+R}$

als Regelstrom zur Ansteuerung der Komponente 1, 8 gesucht wird, der messtechnisch nicht ohne entsprechende Aufbereitung des Signales erfasst werden kann.The output signal of the coil $\frac{1}{\mathit{Ls}+R}$

is a current value i ₁ , which is called the effective value of the coil $\frac{1}{\mathit{Ls}+R}$

is sought as a control current for controlling components 1, 8, which cannot be measured without appropriate processing of the signal.

stellt die Eingangsgröße für einen Hardware-Filter HW zur Filterung des Stromwertes i₁ darstellt, der wiederum den Stromwert i₂ ausgibt, der schließlich die Eingangsgröße für einen Software-Filter SW zur Dämpfung des Signals des Stromwertes i₂ im Steuergerät darstellt, sodass nach dieser Signalverarbeitungskette ein Signal eines Stromwertes is zur Verfügung steht.The current value i ₁ or effective value of the coil $\frac{1}{\mathit{Ls}+R}$

represents the input variable for a hardware filter HW for filtering the current value i ₁ , which in turn outputs the current value i ₂ , which ultimately represents the input variable for a software filter SW for attenuating the signal of the current value i ₂ in the control unit, so that according to this Signal processing chain a signal of a current value is available.

The voltage value u thus represents the input value into the observer module W, whereby the current value i ₃ represents the output value of the signal processing chain, which is also made available to the observer module W, whereby the observer module W has the underlying observer module. Model calculates a new voltage value u in parallel to the previously explained signal processing chain.

This means that the observer W is constantly tracked by the so-called observation error converging to zero, where the observation error is defined as the difference between the measured value i1 and the observed value i3.

This solution according to the invention makes it possible to achieve a high performance and stability of the current detection that meets the requirements, thereby improving the internal current control loops With high performance, the following advantageous properties of the current detection according to the invention by means of observer W can be understood in detail: This type of current detection has only a small phase shift because it is controlled based on the model value of the observer, which corresponds to the real current value, which, however, is only due to the disadvantages of the phase response of the filtering would be recorded after the filter runtime. The detection with an observer is faster, so that the control based on it is also faster. The current detection according to the invention does not require averaging, which means that it is more precise, in particular in contrast to the commonly used PWM-synchronous current detection (with averaging). With the current detection according to the invention, no aliasing effects occur, that is, incorrect signal determination with undersampling, as is the case with other current detection methods, does not occur.

Reference symbol list

100

Kraftstoffversorgungssystem

1

Hochdruckpumpe

2

Vorförderpumpe

3

Kraftstofftank

4

Kraftstoffspeicher, Rail

ΔVRail

Volumen-Regeldifferenz, diskrete Regelabweichung

5

Filtereinheit

6

Duo-Sensor (p, T)

T6

Kraftstofftemperatur

7

Raildruck-Sensor

p7

Raildruck

p7Ist

Ist-Raildruck

p7Ist-max

Ist-Raildruck (diskretisiert Max)

p7Ist-min

Ist-Raildruck (diskretisiert Min)

p7Ist-50%

Ist-Raildruck (diskretisiert Mittelwert)

p7Soll

Soll-Raildruck (diskretisiert)

Δp7 = ΔpRail

diskrete Regelabweichung (druckbezogen)

E

Elastizitätsmodul

8

Druckregelventil

V8

abgesteuerter Volumenstrom über Rücklaufleitung 8.2.1

9n

Injektoren (n-ter Injektor)

91

erster Injektor

92

zweiter Injektor

93

dritter Injektor

94

vierter Injektor

1.4

Hochdruckleitung zwischen 1 und 4

2.1

Niederdruckleitung zwischen 2 und 1

4.9

Injektorleitungen zwischen 4 und 9n

8.2.1

Rücklaufleitung zwischen 8 und 2.1

9.3

Leckagerücklaufleitung zwischen 9n und 3

1.3

HDP-Rücklaufleitung zwischen 1 und 3

S1

erstes Steuergerät

S2

zweites Steuergerät

V_Ges  Gesamt-Volumen (V_9n + V_DLeck + V_{SLeck +} V_{Δp-Rail-Vorgabe})
V_9n  Einspritzvolumen des jeweiligen n-ten Injektors 9n
V_DLeck  Dauerleckagevolumenstrom des Hochdruck-Kraftstoffversorgungssystems
V_SLeck  Schaltleckagevolumenstrom der Injektoren 9n
V_{Δp-Rail-Vorgabe}  Druckänderungswunsch systembedingt
V_ZU  zugeführtes Volumen in Abhängigkeit des Druckänderungswunsches Druckerhöhung
V_Ges-Ab  abgeführtes Volumen in Abhängigkeit des Druckänderungswunsches Druckabsenkung
V_H  konstantes Raumvolumen des Hochdruck-Kraftstoffversorgungssystems
nsync  Startzeitpunkt der Berechnung
A1  Sollwertvorgabe-Baustein des Raildrucks p7_Soll
A2  Sollwert-Diskretisierungs-Baustein
B1  Istwert-Signalerfassungs-Baustein Raildruck p7_Ist
B2  Istwert-Diskretisierungs-Baustein
A2/B2  Regelfehler-Berechnungs-Baustein
A2`/B2`  Umrechnungs-Baustein
C  Regler-Zustandsmaschine
C1  Regel-Baustein der Hochdruckpumpe
C8  Regel-Baustein des Druckregelventils
C1n  Regel-Baustein der Hochdruckpumpe (n-ter Regel-Baustein)
C8n  Regel-Baustein des Druckregelventils (n-ter Regel-Baustein
D  Vorsteuer-Baustein
E  Ausgabe-Baustein
E1  Stellgliedausgabe Hochdruckpumpe
E8  Stellgliedausgabe Druckregelventil
$\frac{1}{\mathbf{Ls}+\mathbf{R}}$

  Spule
u  Spulenspannung
i1  Spulenstrom hinter der Spule
HW  Hardware-Filter
i2  Spulenstrom nach Hardware-Filter
SW  Software-Filter
i3  Spulenstrom nach Software-Filter
W  Beobachter-Baustein

100

Fuel supply system

1

high pressure pump

2

prefeed pump

3

Fuel tank

4

Fuel storage, rail

ΔVRail

Volume control difference, discrete control deviation

5

Filter unit

6

Duo sensor (p, T)

T6

Fuel temperature

7

Rail pressure sensor

p7

Rail pressure

p7Is

Actual rail pressure

p7Actual-max

Actual rail pressure (discretized Max)

p7Actual-min

Actual rail pressure (discretized Min)

p7Is-50%

Actual rail pressure (discretized average)

p7target

Target rail pressure (discretized)

Δp7 = ΔpRail

discrete control deviation (pressure-related)

E

modulus of elasticity

8th

Pressure control valve

V8

controlled volume flow via return line 8.2.1

9n

Injectors (nth injector)

91

first injector

92

second injector

93

third injector

94

fourth injector

1.4

High pressure line between 1 and 4

2.1

Low pressure line between 2 and 1

4.9

Injector lines between 4 and 9n

8.2.1

Return line between 8 and 2.1

9.3

Leakage return line between 9n and 3

1.3

HDP return line between 1 and 3

S1

first control unit

S2

second control unit

V _Total total volume (V _9n + V _DLeck + V _{SLeck +} V _{Δp rail specification} )
V _9n injection volume of the respective nth injector 9n
V _DLeak Continuous leakage volume flow of the high-pressure fuel supply system
V _SLeck Switching leakage volume flow of the injectors 9n
V _{Δp rail specification} Pressure change request is system-dependent
V _TO supplied volume depending on the desired pressure change pressure increase
V _Ges-Ab Dissipated volume depending on the desired pressure change pressure reduction
V _H constant volume of space of the high pressure fuel supply system
nsync Start time of the calculation
A1 Setpoint specification module for rail pressure p7 _setpoint
A2 setpoint discretization block
B1 actual value signal acquisition module rail pressure p7 _actual
B2 actual value discretization block
A2/B2 control error calculation block
A2`/B2` conversion module
C controller state machine
C1 control module of the high-pressure pump
C8 control module of the pressure control valve
C1n control block of the high-pressure pump (nth control block)
C8n control block of the pressure control valve (nth control block
D input control module
E Output block
E1 actuator output high pressure pump
E8 Actuator output pressure control valve
$\frac{1}{\mathbf{Ls}+\mathbf{R}}$

Kitchen sink
u Coil voltage
i1 coil current behind the coil
HW hardware filter
i2 coil current after hardware filter
SW software filter
i3 coil current after software filter
W observer module

Claims (16)

1. Method for controlling a rail pressure (p7_Soll) caused by a high-pressure pump (1) in a fuel accumulator (4) for a fuel supply system (100) of an internal combustion engine, wherein a crank angle-related or cam angle-related fixed angle difference of the internal combustion engine, between an upper dead-center position of a cylinder piston of a cylinder of the internal combustion engine and an upper dead-center position of the pump piston of the high-pressure pump (1) of the fuel supply system (100), is taken into account in the metering of the delivery volume of the high-pressure pump (1), wherein for each segment, which corresponds to a revolution of a crankshaft and thus the movement of the pump piston of the high-pressure pump (1) from the upper dead-center position of the pump piston to the next upper dead-center position, a discretization of a control deviation (Δp₇) of the rail pressure (p7) in the fuel accumulator (4) is carried out repeatedly in a pump-synchronous manner, and a volume-related discrete volume control difference (ΔV_Rail) is calculated from the discrete control deviation (Δp₇), wherein

   the discrete control deviation (Δp₇) is calculated as a difference from the discretized actual rail pressure (p7_Ist) and the discretized setpoint rail pressure (p7_Soll),

   characterized in that

   discretized pressure information (p7_Ist) of a rail pressure sensor (7) of the actively detected pump-synchronous segment is compared with the discretized setpoint rail pressure (p7_Soll) of the pump-synchronous segment that precedes the actively detected segment by a working cycle in order to determine the discrete control deviation (Δp7), wherein

   the volume-related discrete volume control difference (ΔV_Rail) is supplied as an input variable to a control module (C1n) for the high-pressure pump (1) and a control module (C8n) for a pressure control valve (8) assigned to the fuel accumulator (4), wherein the discrete volume control difference (ΔV_Rail) is linked to a pilot control module (D), as a result of which the control variables for the high-pressure pump (1) and the pressure control valve (8) are calculated in an output module (E8) in a pump-synchronous manner for each segment and are supplied to the control elements (E1, E8) of the high-pressure pump (1) and of the pressure control valve (8) for volume-based adjustment of the rail pressure (p7_Soll).
2. Method according to claim 1, characterized in that the discrete control deviation (Δp₇) is calculated as the difference from the discretized actual rail pressure (p7_Ist) and the discretized setpoint rail pressure (p7_Soll) in a cylinder-selective manner by discretized pressure information (p7_Ist) of a rail pressure sensor (7) of the actively detected pump-synchronous segment being compared with the discretized setpoint rail pressure (p7_Soll) of the pump synchronous segment that precedes the actively detected segment by a working cycle, in order to determine the discrete cylinder-selective control deviation (Δp7).
3. Method according to either claim 1 or claim 2, characterized in that the setpoint rail pressure (p7_Soll) is discretized at a time that is determined by a trigger start signal (nsync) which is repeatedly output at the start of a pump-synchronous segment.
4. Method according to claims 1 or 2 and 3, characterized in that the actual rail pressure (p7_Ist) is repeatedly detected and discretized within the segment started by the trigger start signal (nsync).
5. Method according to claim 4, characterized in that the actual rail pressure (p7_Ist), which is repeatedly detected within the pump-synchronous segment, is discretized as

   • the maximum actual rail pressure (p7_Ist-max) in the segment and

   • the minimum actual rail pressure (p7_Ist-min) in the segment and

   • a mean value calculated in the segment (p7_Ist-50%),

   and is optionally compared with the discretized setpoint rail pressure (p7_Soll) in order to determine the discrete control deviation (Δp₇), in particular the discrete cylinder-selective control deviation (Δp₇).
6. Method according to claim 5, characterized in that, for the control, the detected minimum discrete pressure (p7_Ist-min) or the detected maximum discrete pressure (p7_Ist-max) or the discrete mean value (p7_Ist-50%) is used as the actual value (p7_Ist) for comparison with the discrete setpoint rail pressure (p7_Soll), wherein, depending on the system requirement, the maximum discrete pressure (p7_Ist-max) is used in the case of a pressure increase and the minimum discrete pressure (p7_Ist-min) is used in the case of a pressure reduction, in order to reduce control oscillations, in particular to reduce the control oscillations in a cylinder-selective manner, or to prevent overshoots or undershoots, in particular to prevent overshoots or undershoots in a cylinder-selective manner.
7. Method according to either claim 5 or claim 6, characterized in that the discrete control deviation (Δp₇), in particular the discrete cylinder-selective control deviation (Δp₇), is converted into the volume flow-based discrete volume control difference (ΔV₇ = ΔV_Rail), in particular the volume flow-based discrete cylinder-selective volume control difference (ΔV_Rail), wherein, in addition, a permanent fuel leakage (V_DLeck) of the high-pressure system of the fuel supply system is taken into account by addition.
8. Method according to either claim 1 or claim 2, characterized in that the pressure-based discretized control deviation (Δp7 = Δp_Rail) is converted into a volume flow-based volume control difference (ΔV_Rail), wherein the pressure-dependent and temperature-dependent specific modulus of elasticity (E) of the relevant fuel and the spatial volume (V_H) of the high-pressure fuel system of the fuel supply system (100) are taken into account in the conversion in accordance with the conversion formula $\Delta {\mathrm{V}}_{\mathrm{Rail}}=\frac{V_H}{E\left(p,T\right)}*\Delta {\mathrm{p}}_{\mathrm{Rail}}$

   

   , in particular in a cylinder-selective manner.
9. Method according to claims 1 and 8, characterized in that in the pump-synchronous segmental repeated conversion of the pressure-based discrete control deviation (Δp7) into the volume-related discrete volume control difference (ΔV_Rail),

   a) the fuel injection quantities (V_9n) of the injectors (9n), and

   b) the fuel switching leakages (V_SLeck) of the injectors (9n), and

   c) a pressure change request (V_{Δp-Rail-Vorgabe}) with respect to the setpoint rail pressure (p7_Soll) of the fuel accumulator (4) are taken into account, wherein

   d) the permanent fuel leakage (V_DLeck) of the high-pressure system of the fuel supply system (100) is determined by a separate pump-synchronous segmental repeated conversion using a Z transformation, and the volume-related discrete volume control difference (ΔV₇ = ΔV_Rail) is added.
10. Method according to claims 2 and 8, characterized in that in the pump-synchronous segmental repeated conversion of the pressure-based discrete cylinder-selective control deviation (Δp7) into the volume-related discrete volume control difference (ΔV_Rail),

    a) the fuel injection quantities (V_9n) of the injectors (93), and

    b) the fuel switching leakages (V_SLeck) of the injectors (93), and

    c) a pressure change request (V_{Δp-Rail-Vorgabe}) with respect to the setpoint rail pressure (p7_Soll) of the fuel accumulator (4) are taken into account in a cylinder-selective manner, wherein

    d) the permanent fuel leakage (V_DLeck) of the high-pressure system of the fuel supply system (100) is determined by a separate pump-synchronous segmental repeated conversion using a Z transformation, and the volume-related discrete volume control difference (ΔV₇ = ΔV_Rail) is added.
11. Method according to claim 10, characterized in that during steady-state operation, the injectors (9n) receive the same quantity setpoint values from cylinder to cylinder, which values are compared with the quantity decreases (V_9n) from the rail (4) in a cylinder-selective manner, wherein injection quantity errors are determined in a cylinder-selective manner, which errors are assigned to the injectors (9_n), wherein a type of the quantity deviations is assigned to certain error groups.
12. Method according to claim 11, characterized in that the injection quantity errors are grouped according to the cause, in particular the level, of the injection quantity error resulting from the setpoint/actual comparison of the injection quantity error, wherein, during operation, the injectors (9n) are assigned to an error group with an injector defect, an error group with an aging-related injector drift, or an error group with a changing switching leakage quantity (V_SLeck), wherein the injection quantity errors are determined within the cylinder-selective control in the controller (C1_n, C8_n) and corrected in the injection system and/or lead to an exchange of the relevant injector/injectors (9n).
13. Method according to either claim 1 or claim 2, characterized in that the control variables of the control elements of the components (1, 8) for controlling the rail pressure (p7_Soll) in the fuel accumulator (4) are supplied to an output module (E1, E8) and are calculated in the output module (E1, E8) for volume-based adjustment of the rail pressure (p7_Soll), wherein current detection and current control of the control elements (1, 8) are carried out on the basis of an observer model.
14. Fuel supply system (100) designed to carry out the method according to at least one of claims 1 and 3 to 9, characterized in that, in order to determine

    • a discrete input variable for a controller module (C1) for the high-pressure pump (1) and to determine a discrete input variable for a controller module (C8) for a pressure control valve (8) assigned to the fuel accumulator (4), the fuel supply system (100) comprises the following further modules,

    • a setpoint value specification module (A1) of the rail pressure (p7_Soll) and an associated setpoint value discretization module (A2), and

    • an actual value signal detection module (B1) of the rail pressure (p7_Ist) and an actual value discretization module (B2),

    • and a control error calculation module (A2/B2), and

    • comprises a conversion module (A2'/B2') which carries out a conversion into a volume flow-based control difference (ΔV_Rail) from a pressure-based discretization control deviation (Δp7 = Δp_Rail), wherein

    • the conversion module (A2'/B2') is linked to a controller state machine (C) which outputs the discrete input variable for the controller module (C1) of the high-pressure pump (1) and the discrete input variable for the controller module (C8) of the pressure control valve (8),

    • wherein the controller modules (C1, C8) are linked to a pilot control module (D), as a result of which, by means of the pilot control module (D) and the connected controller modules (C1, C8), the control variables for the high-pressure pump (1) and the pressure control valve (8) are supplied to an output module (E8) and calculated for each segment in a pump-synchronous manner, and are supplied to the control elements (E1, E8) of the high-pressure pump (1) and the pressure control valve (8) for volume-based adjustment of the rail pressure (p7_Soll).
15. Fuel supply system (100) designed to carry out the cylinder-selective method according to at least one of claims 1 to 13, characterized in that the fuel supply system (100) comprises

    • in a cylinder-selective manner, a plurality (n) of controller modules (C1n) for the high-pressure pump (1) for determining the relevant discrete input variable of the relevant cylinder, and a plurality (n) of controller modules (C8n) for a pressure control valve (8) assigned to the fuel accumulator (4) for determining the relevant discrete input variable of the relevant cylinder, and

    • a setpoint value specification module (A1) of the rail pressure (p7_Soll) and an associated setpoint value discretization module (A2), and

    • an actual value signal detection module (B1) of the rail pressure (p7_Ist) and an actual value discretization module (B2),

    • and a control error calculation module (A2/B2), and

    • a conversion module (A2'/B2') which carries out a conversion into a volume flow-based control difference (ΔV_Rail) from a pressure-based discretization control deviation (Δp7 = Δp_Rail), wherein

    • the conversion module (A2'/B2') is linked to a controller state machine (C) which outputs the discrete input variable to the relevant controller module (C1n) of the high-pressure pump (1) in a cylinder-selective manner, and outputs the discrete input variable to the relevant controller module (C8n) of the pressure control valve (8) in a cylinder-selective manner,

    • wherein the controller modules (C1n, C8n) are each linked to a pilot control module (D) in a cylinder-selective manner, as a result of which, by means of the pilot control module (D) and the connected cylinder-selective controller modules (C1, C8), the control variables for the high-pressure pump (1) and the pressure control valve (8) are supplied to an output module (E8) and calculated for each segment in a pump-synchronous manner, and are supplied to the control elements (E1, E8) of the high-pressure pump (1) and the pressure control valve (8) for volume-based cylinder-selective adjustment of the rail pressure (p7_Soll).
16. Fuel supply system (100) according to either claim 14 or claim 15, characterized in that the fuel supply system (100) comprises an observer module (W), which monitors a signal processing chain ( $\frac{1}{\mathrm{LS}+\mathrm{R}}$

    

    , HW, SW) for current detection and current control of the control elements (1, 8) of the fuel supply system (100).

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