EP0445339A1 - Engine idling control system - Google Patents

Abstract

An engine idling control system with loss and disturbance-variable feedback from an observer unit, in which the total mechanical losses of the internal combustion engine (MvM) including the energy consumption of all instantaneously connected auxiliary units (MvA) are reconstructed in the observer unit (B) with a predetermined time constant (h1), for which purpose the observer unit (B) receives as input variables the angular velocity ( omega ) of the internal combustion engine and the work MI performed by the gas in its combustion chamber (MI = INTEGRAL o<v>pIdV, pI being the indicated mean pressure and V being the displacement), and in which the minimum torque (Mv) required for reliable idling, reconstructed by the observer unit, is added as a reference variable component to the variable corresponding to the mixture (G) fed in, in order to compensate the latter. <IMAGE>

Description

The present invention relates to an idle control system for an internal combustion engine, with a loss and disturbance variable feedback from an observer unit.

Conventional idle speed controllers obtain the control intervention for idling superimposed on the internal combustion engine precontrol exclusively from a setpoint / actual value comparison of the engine speed, see FIG. 1. In order to keep overshoots and / or drops in the idle speed as small as possible, a PID ( P roportional- I ntegral- ifferential- D) controller, comp. example Leonhard "introduction to control Engineering", Vieweg, used, which can react already on the gradient of an "imminent" speed burglary.

• a) der großen Tot- und Verzögerungszeiten zwischen der Stellgröße "Gemischeinbringung" und der im Brennraum freigesetzten Gasarbeit (M_I), sowie
• b) der zu beschleunigenden Trägheitsmassen (J) von Motor und Hilfsantrieben

müssen hochverstärkende DT₁-Regelparameter angesetzt werden. Hohe D-Anteile begünstigen jedoch bekannterweise ein instabiles Regelverhalten (aufschwingende Eigenbewegung), was zu einer drastisch erhöhten Emission, einem erhöhtem Verbrauch und im Extremfall zum "Abwürgen" des Motors führen kann. Um bei ungenügend beherrschbaren Oszillationen ein "Abwürgen" des Motors zu verhindern, wird die Leerlaufdrehzahl üblicherweise um einen Sicherheitsreserve-Betrag höher eingestellt.Because of

• a) the large dead and delay times between the manipulated variable "mixture introduction" and the gas work released in the combustion chamber (M _I ), and
• b) the inertial masses (J) to be accelerated of the engine and auxiliary drives

high-gain DT 1 control parameters must be applied. However, high D components are known to favor unstable control behavior (self-oscillating movement), which can lead to drastically increased emissions, increased consumption and, in extreme cases, "stalling" of the engine. In order to prevent "stalling" of the engine in the case of insufficiently controllable oscillations, the idling speed is usually set higher by a safety reserve amount.

In order to improve the behavior of reference variables with regard to a), Kiencke U., VDI-Ber. 612 (1986) "Design of a state controller for idle control of a gasoline engine "is a state control loop with feedback of the intake manifold pressure. This known state control loop is robust against leaps in command variables (accelerator pedal), but can only change changes in loss and disturbance variables (mechanical losses during warm-up, auxiliary drives to be switched on) to a limited extent, namely via the conventional speed Setpoint / actual value comparison and compensate by additional heuristic interventions.

To improve the behavior of disturbance variables with regard to b), only precontrols have been implemented using experience models, in which state parameters, such as Engine temperature, air mass, mixing ratio and speed as well as switch signals from auxiliary drives.

The present invention has for its object to provide an idle control system of the type mentioned, which is capable of the idle speed with a state controller that detects both the operating point-dependent mechanical losses and the mechanical system engine disturbing elements with an observer unit and compensating the mixture feed switches to regulate.

To solve the problem, an idle control system is proposed in which the total mechanical losses of the internal combustion engine, including the energy requirements of all auxiliary units currently switched on, are reconstructed in the observer unit with a predetermined time constant, for which purpose the observer unit uses the angular velocity of the internal combustion engine and the gas work released in its combustion chamber as input variables are supplied and the idle torque reconstructed by the observer unit of the quantity corresponding to the mixture supplied is added to compensate as a reference variable component in order to achieve an ideal disturbance variable behavior.

Advantageous developments of the invention are characterized by the features specified in the subclaims.

The invention offers the advantage that the running limit (this is the minimum speed from which "stalling" can no longer occur when idling) can be further reduced and the smoothness can be improved. Since consumption and emissions decrease approximately proportionally with the speed, this can be used especially in city traffic, see e.g. Bosch technical briefing "Motronic" Sept. 1985, p. 26, and in the warm-up phase, improvements can be achieved.

With the help of the torque required by the observer unit in real time for idle operation, the required amount of mixture can be determined well in advance, and the operation of the control loop is no longer initiated solely by the speed setpoint / actual value comparison alone.

With this, the control adapts e.g. the engine friction falling during warm-up or the varying energy requirements of the auxiliary drives. The feedback of the state from the "loss observer", namely the observer unit, can also compensate for arbitrary disturbance variable feeds (such as switching on the air conditioning system, servomotors and the like) without overwhelming the speed controller, taking into account a settling time of the observer unit.

The invention eliminates all the disadvantages associated with a (previously explained) "pilot control of the required idling torque" by the observer reconstructing this quantity from the comparison of the gas work (M _I ) released in the combustion chamber with the dynamics of the engine speed (dn / dt) and the introduction of the mixture pretends as a command component.

When using the known method of pole specification, the dynamic behavior of the overall system can be predetermined by appropriately acting on the control variable “mixture introduction” with feedbacks formed from the state variables “intake manifold pressure” and “idling torque”.

The invention is described in detail below with reference to several figures.

Fig. 1

den Funktionsplan eines Zustandsregelkreises für ein gutes Führungsverhalten nach dem Stand der Technik gemäß Kiencke U., VDI-Ber. 612(1986) ("Entwurf eines Zustandsreglers für die Leerlaufregelung eines Ottomotors");

Fig. 2

den Funktionsplan eines sog. Beobachtermodells zur Rekonstruktion der "mechanischen Verluste im Leerlaufbetrieb" nach dem Stand der Technik, dem eine Beobachtereinheit B gemäß der Erfindung zugefügt ist;

Fig. 3

das Prinzipschaltbild der Beobachtereinheit B in einer Analogschaltungsanordnung;

Fig. 4

den Funktionsplan einer Beobachtereinheit B gemäß der Erfindung für die "Beobachtung der mechanischen Verluste" in einer Digitalschaltungsanordnung;

Fig. 5

den Funktionsplan einer Verlust- und Störgrößenrückführung in einem Leerlaufregelsystem gemäß der Erfindung.

It shows:

Fig. 1

the functional diagram of a state control loop for good leadership behavior according to the state of the art according to Kiencke U., VDI-Ber. 612 (1986) ("Design of a State Controller for the Idle Control of a Gasoline Engine");

Fig. 2

the functional diagram of a so-called observer model for the reconstruction of the "mechanical losses in idle mode" according to the prior art, to which an observer unit B according to the invention has been added;

Fig. 3

the basic circuit diagram of the observer unit B in an analog circuit arrangement;

Fig. 4

the functional diagram of an observer unit B according to the invention for the "observation of mechanical losses" in a digital circuit arrangement;

Fig. 5

the functional diagram of a loss and disturbance variable feedback in an idle control system according to the invention.

mit

ṁ_G,zu

: dem Einlaßtrakt zugeführte Gemischmasse   [kg/s]

ṁ_G,ab

: vom Einlaßtrakt abgesaugte Gemischmasse   [kg/s]

K_IS

: Saugrohr-Integrationskonstante   [N/m²s]

R

: spezielle Gaskonstante

K

: Adiabatenexponant   [ca. 1,40]

T_S

: Temperatur im Ansaugrohr

V_S

: Volumen des Ansaugrohrs

Indizes" ̇"

: Ableitung nach der Zeit

M_e ^*

: in einem Kennfeld abgelegtes effektives Motormoment (aus stationären Prüfstandsversuchen)   [Nm]

M_I

: alternativ zu M_e ^* . (1-e^-t/ts) e^{-t/tt . 2π}   [Nm] falls Brennraumdruck-Messung vorhanden   [Nm]

J

: Trägheitsmoment des Motors inklusive aller im Leerlauf aktivierten Aggregate   [kgm²]

n

: Motordrehzahl   [S^-1]

weitere Nomenklatur siehe Fig. 1.

${\text{M}}_{\text{v}}{\text{= M}}_{\text{vn}}{\text{+ M}}_{\text{vz}}$

M_vn

= permanente mechan. Verluste im Leerlauf

M_vz

= zuschaltbare mechan. Verluste im Leerlauf

${\text{f}}_{\text{M}}{\text{= (1 - e}}^{\text{-t/ts}}{\text{) . e}}^{\text{-j t/tt . 2π}}$

f_M

= vereinfachte math. Funktion für Zeitverhalten der thermodyn. Energieumsetzung im Motor.

The differential equation of the previously known (Kiencke, U.) idle state control loop is:

With

ṁ _{G, too}

: mixture mass fed to the inlet tract [kg / s]

ṁ _{G, from}

: mixture mass extracted from the inlet tract [kg / s]

K _IS

: Intake pipe integration constant [N / m²s]

R

: special gas constant

K

: Adiabatic exposure [approx. 1.40]

T _S

: Temperature in the intake pipe

V _p

: Volume of the intake pipe

Indices "̇"

: Derivation by time

M _e ^*

: Effective engine torque stored in a map (from stationary test bench tests) [Nm]

M _I

: alternative to M _e ^* . (1-e ^{-t / ts} ) e ^{-t / tt. 2π} [Nm] if combustion chamber pressure measurement is available [Nm]

J

: Moment of inertia of the motor including all aggregates activated when idling [kgm²]

n

: Engine speed [S ^-1 ]

for further nomenclature see FIG. 1.

${\text{M}}_{\text{v}}{\text{= M}}_{\text{vn}}{\text{+ M}}_{\text{vz}}$

M _vn

= permanent mechan. Idle losses

M _vz

= switchable mechan. Idle losses

${\text{f}}_{\text{M}}{\text{= (1 - e}}^{\text{-t / ts}}{\text{). e}}^{\text{-jt / tt. 2π}}$

f _M

= simplified math. Function for time behavior of the thermodyne. Energy conversion in the engine.

In order to make the idle controller according to FIG. 1 also adaptive to the operating point-dependent mechanical losses (in particular warm-up behavior) and robust to interference torques by auxiliary drives to be switched on, an observer model is introduced for the reconstruction of these loss and interference variables.

State equations of the observer:

$\text{v = ∫(}\dot{\text{v}}\text{. dt)}$

${\hat{\text{M}}}_{\text{v}}\text{= v - (h₁ . J . dφ/dt)}$

mit

v

: beobachterinterne Signalgröße

v

: deren Zeitableitung

h₁

: die entsprechend der gewünschten Güteklasse festgelegte Zeitkonstante für das Abklingen des dynamischen Rekonstruktionsfehlers,   [S⁻¹]

dφ/dt

: motordrehzahlabh. Impulsfrequenz von einer Kurbelwellenindizierung in s^-1 als Winkelgeschwindigkeit

M_I

: alternativ zu M_e ^*, falls Brennraumdruck-Messung vorhanden

J

: Trägheitsmoment des Motors inklusive aller im Leerlauf aktivierten Aggregate

M_v

: die "vom Beobachter rekonstruierten" mechanischen Verluste (inkl. Hilfsantriebe)

Indizes" ̂"

: für über Beobachterschaltung rekonstruierte Abbilder einer physikalischen Größe .

$\dot{\text{v}}{\text{= (-h₁. v) + (h₁. M}}_{\text{I.}}\text{) + (h₁². J. dφ / dt)}$

$\text{v = ∫ (}\dot{\text{v}}\text{. dt)}$

${\hat{\text{M}}}_{\text{v}}\text{= v - (h₁. J. dφ / dt)}$

With

v

: internal signal size

v

: their time derivative

h₁

: the time constant for the decay of the dynamic reconstruction error, determined according to the desired quality class, [S⁻¹]

dφ / dt

: engine speed dependent Pulse frequency from a crankshaft indexing in s ^-1 as angular velocity

M _I

: alternative to M _e ^* if combustion chamber pressure measurement is available

J

: Moment of inertia of the motor including all aggregates activated at idle

M _v

: the "losses reconstructed by the observer" (including auxiliary drives)

Indices "̂"

: for images of a physical quantity reconstructed using an observer circuit.

2 shows, as previously indicated, the functional diagram of a so-called observer model for the reconstruction of the "mechanical losses in idle mode" according to the prior art, to which an observer unit B according to the invention is fed.

Since the "active moment of inertia" J changes slightly as soon as auxiliary drives switch on or off, it is therefore switched on using switch messages or the control commands of the connected units
or adapted from an experience model implemented in the observer.
The empirical model records the time course of a "disturbance torque" that has only been qualitatively reconstructed in the first work step and compares it with the known switchable units that are possible.

, wobei p_I der indizierte Mitteldruck und V das Hubvolumen ist) zugeführt werden und daß das von der Beobachtereinheit rekonstruierte Leerlaufdrehmoment M_v der dem zugeführten Gemisch G entsprechenden Größe als Führungsgrößenkomponente kompensierend aufaddiert wird (Fig. 3), um ein möglichst ideales Störgrößenverhalten zu erzielen.According to the invention it is provided that the entire mechanical Losses of the internal combustion engine M _vM, including the energy requirement of all auxiliary _units M _{vA that are} currently switched on, are _{reconstructed} in the observer unit B with a predetermined time constant h 1, for which purpose the observer unit B as input variables the angular velocity ω of the internal combustion engine and the gas work M _I (released in its combustion chamber) ${\text{M}}_{\text{I.}}{\text{= ∫₀}}^{\text{v}}{\text{p}}_{\text{I.}}\text{dV}$

, where p _{I is} the indicated mean pressure and V is the stroke volume) and that the idle torque M _v reconstructed by the observer unit is added to compensate as a reference variable component (Fig. 3) in order to achieve an ideal disturbance behavior .

$\text{V = ∫ (}\dot{\text{v}}\text{. dt)}$

${\hat{\text{M}}}_{\text{v}}\text{= v - (h₁. J . d φ /dt)}$

mit

v:

beobachterinterne Signalgröße

v:

deren Zeitableitung

h₁:

die entsprechend der gewünschten Güteklasse festgelegte Zeitkonstante für das Abklingen des dynamischen Rekonstruktionsfehlers   [s^-1]

dφ/dt :

Impulse von einer Kurbelwellenindizierung

M_I:

alternativ zu M_e ^*, falls Brennraumdruck-Messung vorhanden,

J :

Trägheitsmasse der Brennkraftmaschine einschließlich aller im Leerlauf aktivierten Aggregate   [kgm²],

M̂_v:

die von der Beobachtereinheit B rekonstruierten mechanischen Verluste (einschließlich Hilfsaggregate)   [Nm].

According to one embodiment of the invention, the observer unit B works analogously (see FIG. 3) and reconstructs an output variable M _v from the input variables ω, M _I according to the equations

$\dot{\text{v}}{\text{= (-h₁ .v) + (h₁. M}}_{\text{I.}}\text{) + (h₁². J. dφ / dt)}$

$\text{V = ∫ (}\dot{\text{v}}\text{. dt)}$

${\hat{\text{M}}}_{\text{v}}\text{= v - (h₁. J. d φ / dt)}$

With

v:

internal signal size

v:

their time derivative

h₁:

the time constant for the decay of the dynamic reconstruction error determined according to the desired quality class [s ^-1 ]

dφ / dt:

Pulses from a crankshaft indexing

M _I :

alternative to M _e ^* , if combustion chamber pressure measurement is available,

J:

Inertia mass of the internal combustion engine including all aggregates activated when idling [kgm²],

M̂ _v :

the mechanical losses reconstructed by observer unit B (including auxiliary units) [Nm].

allgemein:

U_(n)T

: Ausdruck für den Steuervektor des Systems zum Tastzeitpunkt n·T

V_(n)T

: allgem. Ausdruck für den Zustandsvektor des Systems zum Tastzeitpunkt

According to another embodiment, the observer unit B works digitally (see FIG. 4) and forms an output variable Mv _{(n) T} from the input variables ω, M _I according to the algorithm according to the equations

general:

U _{(n) T}

: Expression for the control vector of the system at the moment of scanning n · T

V _{(n) T}

: general Expression for the state vector of the system at the moment of scanning

It is provided according to the invention that the inertial mass J is adapted by means of switch messages or from the control signals of the connected auxiliary units and in the analog circuit (FIG. 3) switches corresponding capacitors to C in parallel.

If the combustion chamber pressure indexing is not available, the released gas work is called up via map values k4 and k5 (FIG. 1).

A settling time that is unavoidable in the observer unit (B) (= decay time of the dynamic reconstruction error) is compensated for by an appropriately dimensioned differential component (lead) in a disturbance variable controller (FIG. 3).

The input variables and the variable corresponding to the internal signal variable v are sampled with a switch S1 and buffered. A hold and delay element (z ^-1 ) carries out the processing of the observer-internal signal quantity v by delaying it by a sampling interval T. The digital observer unit B stores as many sampling times (n) T, (n + 1) T, ... as it is System order of the observer unit B corresponds.

An adaptation of the "activated inertial mass", which changes slightly as soon as auxiliary drives are switched on or off, is carried out by an experience model implemented in the observer unit B, which records the time profile of an "interference torque" that is only qualitatively reconstructed in a first work step and this with it compares the time profiles known to him for all switchable auxiliary drives.

Since this work has now shown how the mechanical losses of the engine when idling (including the energy for the connected auxiliary drives) can be reconstructed with an observer, the engine model (1t. Fig. 1) may be extended by this "energy sink". The result is an idle control, which is not only robust against gas shocks by the driver, but also - adaptable to the warm-up behavior, to mechanical changes due to aging, to specimen scatter and - robust to disturbing torques, introduced by switching auxiliary drives.

${\text{M}}_{\text{v}}{\text{= M}}_{\text{vn}}{\text{. n + M}}_{\text{vo}}$

${\text{f}}_{\text{m}}{\text{= (1 - e}}^{\text{-t/ts}}{\text{) . e}}^{\text{-jtt}}$

The differential equation of the "idle torque robust" is:

${\text{M}}_{\text{v}}{\text{= M}}_{\text{vn}}{\text{. n + M}}_{\text{vo}}$

${\text{f}}_{\text{m}}{\text{= (1 - e}}^{\text{-t / ts}}{\text{). e}}^{\text{-jtt}}$

${\text{- h₁T}}_{\text{B}}\text{= ln 10\% = -2.30}$

h₁ = 23 s^-1

${\text{A = e}}^{\text{-h₁T}}{\text{= e}}^{\text{-23·0.01}}\text{= 0.80}$

J = 3.02 kgm² (Forschungsmotor AVL-Einzylinder mit V_z=400cm³

In the case of test measurement series, the following average values for the individual variables resulted for a sampling period T = 10 ms and a selected reconstruction time of T _B = 100 ms:

${\text{- h₁T}}_{\text{B}}\text{= ln 10\% = -2.30}$

h₁ = 23 s ^-1

${\text{A = e}}^{\text{-h₁T}}{\text{= e}}^{\text{-23 · 0.01}}\text{= 0.80}$

J = 3.02 kgm² (research engine AVL single cylinder with V _z = 400cm³

Claims (8)

Idle control system for an internal combustion engine, with a loss and disturbance variable feedback from an observer unit,
characterized , - That the total mechanical losses of the internal combustion engine (M _vM ) including the energy requirements of all auxiliary _units (M _vA ) currently switched on in the observer unit (B) are reconstructed with a predetermined time constant (h 1), for which purpose the observer unit (B) as the input variables the angular velocity ( $\text{ω = dφ / dt}$

) of the internal combustion engine and the gas work M _I released in its combustion chamber ( ${\text{M}}_{\text{I.}}{\text{=}}^{\text{v}}{\text{∫}}_{\text{O}}{\text{p}}_{\text{I.}}\text{dV}$

, where p _{I is} the indicated mean pressure and V is the stroke volume) and - That the idle torque (M _v ) reconstructed by the observer unit of the quantity corresponding to the mixture (G) supplied is added up as a compensating variable component (FIG. 3) in order to achieve the ideal disturbance variable behavior. Idle control system according to claim 1,
characterized ,
that the observer unit (B) works analogously and from the input variables (, M _I ) an output variable (M _V ) according to the equations

$\dot{\text{v}}{\text{= (-h₁. v) + (h₁ M}}_{\text{I.}}\text{) + (h₁². J d φ / dt)}$

$\text{V = ∫ (}\dot{\text{v}}\text{dt)}$

${\hat{\text{M}}}_{\text{v}}\text{= v - (h₁. J .dφ / dt)}$

With v: internal signal size v: their time derivative h₁: the time constant for the decay of the dynamic reconstruction error, determined according to the desired quality class, [s ^-1 ] φ: pulses from a crankshaft indexing M _I : alternative to M _e ^* , if combustion chamber pressure measurement is available, J: inertial mass of the internal combustion engine including all units activated when idling [kgm²] M̂ _v : the mechanical losses (including auxiliary units) reconstructed by the observer unit (B) [Nm] reconstructed. Idle control system according to claim 1,
characterized ,
that the observer unit (B) works digitally and from the input variables (, M _I ) an output variable (M _{(n) T} ) according to the equations

reconstructed. Idle control system according to claim 2,
characterized ,
- That the inertial mass (J) is adapted by means of switch messages or from the control signals of the connected auxiliary units and in the analog circuit (2b) switches corresponding capacitors to (C) in parallel. Idle control system according to claim 3,
characterized ,
that if the combustion chamber pressure indexing is not available, the released gas work is called up via map values (k4) and (k5) (FIG. 1). Idle control system according to claim 2 or 3,
characterized ,
that an inevitable settling time in the observer unit (B) (= decay time of the dynamic reconstruction error) is compensated for by an appropriately dimensioned differential component (lead) in a disturbance variable controller (FIG. 3). Idle control system for an internal combustion engine, with a loss and disturbance variable feedback from an observer unit according to one of the preceding claims,
characterized , that the input variables and the variable corresponding to the internal signal variable (v) are sampled and buffered with a switch (S1), - That a hold and delay element (z ^-1 ) executes the processing of the internal signal size (v) by delaying a sampling interval (T) and - That the digital observer unit (B) temporarily stores as many sampling times ((n) T, (n + 1) T, ...) as corresponds to the system order of the observer unit (B). Idle control system according to one of the preceding claims,
characterized ,
that an adaptation of the "activated inertial mass", which changes slightly as soon as auxiliary drives switch on or off, is carried out by an experience model implemented in the observer unit (B), which takes up the time profile of a "disturbing torque" which is only qualitatively reconstructed in a first operation and compares this with the time curves known to him for all switchable auxiliary drives.

Images