DE10262105B4 - Air-fuel ratio control apparatus for internal combustion engine, identifies plant model using actual air-fuel ratio and valve obtained by adding offset correction amount to feedback control amount of control signal - Google Patents

Abstract

A controller (22) sets the feedback control amount of the air-fuel ratio control signal using parameters of identified plant model which represents a plant between the fuel injection valve (5) and sensor (13) by transfer function. The plant model is identified by using the actual air-fuel ratio and value obtained by adding offset correction amount to feedback control amount. An independent claim is also included for air-fuel ratio control method.

Description

The The present invention relates to a device for controlling the Air / fuel ratio in an internal combustion engine according to the preamble of the independent Patent claim 1, and a method for controlling the air / fuel ratio in an internal combustion engine according to the preamble of the independent Patent claim 8.

Such a device or method for controlling the air / fuel ratio in an internal combustion engine is from the publication DE 195 16 239 C2 known. In particular, the cited document relates to a method for parameterizing a linear lambda controller for an internal combustion engine. In this method for parameterizing a lambda controller of a lambda control device with a lambda probe, its output signal shows at least partially a linear dependence on the oxygen content in the exhaust gas of the internal combustion engine. The transfer function of the lambda control system is represented by the series connection of two delay elements of the first order and a dead time element in the lambda control circuit, and the first delay element contains the response of the lambda sensor, the second delay element includes a sliding mean value of the lambda values, wherein the lambda controller a proportional-integral-derivative (PID) controller is used.

at an internal combustion engine becomes ordinary an air / fuel ratio controlled to a target value, to exhaust purification and fuel economy to improve.

A technical teaching for performing such control of the air-fuel ratio with high accuracy in which a time-out compensation control by the Smith method is performed is given in an apparatus for controlling the air-fuel ratio of an internal combustion engine (not Japanese Examined Patent Publication No. 2001-164971 or US Pat. No. 6,453,229 B1 ) to calculate a control amount of a fuel injection amount by a sliding mode control.

A Such device for controlling the air / fuel ratio may be constructed such that a rule gain of Sliding mode control is calculated by a self-adjusting control. In this device for controlling the air / fuel ratio the controlled variable will be as follows calculated.

One Plant model, the means of a transfer function a controlled system between the fuel injector and the air-fuel ratio detection means is sequentially based on a fuel injection amount and an actual one Air / fuel ratio identified.

Then is using this identified controlled system model (Parameters) the entire system including the controlled system, one Control variable calculation section (in other words, a sliding mode control section) and a Auszeitkompensations control section through a transfer function reproduced, wherein a control gain of the sliding mode control is calculated so that one pole of the transfer function with a desired Pol as regards response characteristic, excess, stabilization period etc. coincides.

Then becomes the controlled variable of the fuel injection amount calculated by the sliding mode control using the calculated control gain, to a control of the air / fuel ratio in accordance with a characteristic change Perform in the control system with high accuracy.

It However, it has been found that in such a controller the air / fuel ratio Improvements possible are, for example, when processing fixed offset correction values such as an air-fuel ratio learning value and a water temperature correction value next to the controlled variable and at during processing an open control, if no control is performed during a Fuel cut, and while the resumption of the scheme and continue to apply in case that the scheme is not carried out although the regulatory conditions are met.

The publication DE 36 13 570 A1 relates to a control system for the feedback control of the fuel-air mixture of an internal combustion engine, which may be an automotive engine, using an oxygen sensor for detecting the instantaneous value of the air-fuel ratio due to the oxygen concentration in the exhaust gas. The control system has the task of temporarily switching the feedback control of the air-fuel ratio to an open-loop control, when one of a plurality of predetermined transient operating conditions of the engine is detected. In order to resume the intermittent feedback control at an optimum timing, the air-fuel ratio control system includes means for detecting the warm-up degree of the engine and means for variably determining the duration of the open loop control according to the detected warm-up degree of the engine.

The publication DE 33 12 409 A1 shows an air-fuel ratio control device in which an error in the air-fuel ratio is corrected so that the feedback control is performed at least once for a predetermined period of time during a high load range of the engine, and that the operation in High load range is carried out thereon by means of an open-loop control on the basis of the results obtained during the feedback control.

It The object of the present invention is a device and a method for controlling the air / fuel ratio in an internal combustion engine of the type mentioned, wherein the control is carried out in a simple and efficient manner.

According to the device aspect the said object is achieved by a device for Controlling the air / fuel ratio in an internal combustion engine with the features of the independent claim 1.

preferred Further developments of the subject invention are set forth in the dependent claims.

According to the method aspect the object is achieved according to the invention by a method for Controlling the air / fuel ratio in an internal combustion engine with the features of the independent claim 8th.

preferred Further developments of the subject invention are set forth in the dependent claims.

According to one embodiment, the following basic steps are provided:
Determining an actual air / fuel ratio by an air / fuel ratio sensor based on an exhaust condition; Generating an air-fuel ratio control signal including a control amount based on the actual air-fuel ratio when no control is performed; and injecting an amount of fuel in accordance with the target air-fuel ratio through a fuel injection valve receiving the air-fuel control signal; further including the following steps:
Calculating parameters of transfer functions while sequentially identifying a plant model representing a control path between the fuel injection valve and the air-fuel ratio sensor by the transfer functions;
Determining the controlled variable of the air / fuel ratio control signal using the parameters of the identified controlled system model,
Setting an offset correction amount of the air-fuel ratio control signal, and
Identifying the controlled system model using a value obtained by adding the offset correction quantity to the controlled variable and the actual air / fuel ratio.

According to a further embodiment, in addition to the basic steps mentioned above, the following steps are also provided:
Calculating parameters of transfer functions while sequentially identifying a plant model representing a control path between the fuel injection valve and the air-fuel ratio sensor by the transfer functions;
Calculating a control gain for calculating the controlled variable of the air-fuel ratio control signal using the parameters of the identified controlled-system model,
Calculating the controlled variable using the calculated control gain, and
Preventing the calculation of the controlled variable under a predetermined operating condition when no control is performed.

According to a further embodiment, in addition to the basic steps mentioned above, the following steps are also provided:
Calculating parameters of transfer functions while sequentially identifying a plant model which reproduces a control path between the fuel injection valve and the air-fuel ratio sensor by the transfer functions;
Calculating a control gain for calculating the controlled variable of the air-fuel ratio control signal using the parameters of the identified controlled-system model,
Calculating the controlled variable using the calculated control gain,
Storing an air / fuel ratio control signal value and the actual air / fuel ratio while performing an open control,
Stopping the calculation of the parameters of the controlled system model during the execution of a control, and
Using the stored air / fuel ratio control signal value and the actual air / fuel ratio as input / output data for the controlled system, when the calculation of the parameters of the controlled system model is resumed after completion of the open control.

According to a further embodiment, in addition to the basic steps mentioned above, the following steps are also provided:
Calculating parameters of transfer functions while sequentially identifying a plant model representing a control path between the fuel injection valve and the air-fuel ratio sensor by the transfer functions;
Determining the controlled variable of the air / fuel ratio control signal by a sliding mode control based on the parameters of the identified controlled system model,
Deciding whether a control direction of the controlled variable and a direction of change of the actual air / fuel ratio coincide with each other, and
Preventing setting of the controlled variable when the control direction of the controlled variable and the amount of change of the actual air / fuel ratio do not coincide with each other.

following The present invention will be related to embodiments with the attached Drawings closer described and explained. In the drawings show:

1 Fig. 16 is a diagram showing a hardware system for the embodiments.

2 FIG. 10 is a block diagram showing control of the air-fuel ratio in an internal combustion engine according to a first embodiment; FIG.

3 FIG. 10 is a block diagram showing a time-out compensation control in the first embodiment; FIG.

4 is a table for calculating the time-out used in the first embodiment;

5 is a block diagram illustrating a sliding mode control section 221 and a time-out compensator 222 by transfer functions in the first embodiment,

6 Fig. 10 is a block diagram showing an overall control of the air-fuel ratio by a sliding mode control using a self-adjusting control in the first embodiment;

7 FIG. 10 is a block diagram showing a control of the air-fuel ratio of the internal combustion engine according to a second embodiment; FIG.

8th FIG. 10 is a block diagram showing a control of the air-fuel ratio of the internal combustion engine according to a third embodiment; FIG.

9 FIG. 10 is a block diagram showing a control of the air-fuel ratio of the internal combustion engine according to a fourth embodiment; FIG.

10 FIG. 12 is a flowchart showing a control of a second controlled variable computation prevention section in the fourth embodiment; and FIG

11 FIG. 10 is a block diagram showing a control of the air-fuel ratio of the internal combustion engine according to a sixth embodiment. FIG.

As in 1 shown are an air flow meter 3 , which detects an intake air amount Qa, and a throttle valve 4 , which controls the intake air amount Qa, in an intake passage 2 an engine 1 arranged.

Furthermore, a fuel injection valve 5 at the inlet channel 2 by an injection signal from a control unit 6 opened with a microcomputer to supply and inject fuel.

There is a spark plug in each cylinder 8th for ignition in a combustion chamber 7 arranged one by the inlet valve 9 to ignite aspirated air / fuel mixture by a spark ignition.

The combustion exhaust gas is passed through an exhaust valve 10 in an exhaust duct 11 discharged and via an exhaust gas purification device 12 output to the circulating air.

A wide range sensitive air / fuel ratio sensor 13 that detects linear air-fuel ratio in accordance with the oxygen concentration in the exhaust gas is before the exhaust gas purification device 12 in the exhaust duct 11 arranged.

Furthermore, a rotation angle sensor 14 which receives a rotation angle signal every predetermined rotation angle of the motor 1 and a water temperature sensor 15 provided, which has a cooling water temperature Tw within a cooling jacket of the engine 1 finds.

The control unit 6 controls the fuel injection valve 5 as follows.

First, a basic injection amount Tp = K · Qa · Ne (where K is a constant) in accordance with a stoichiometric air-fuel ratio (λ = 1) from the intake air amount Qa and a motor rotation speed Ne based on the signal of the rotation angle sensor 14 is determined, calculated.

Then, it is decided in accordance with operating conditions whether the air / fuel ratio is controlled or openly controlled. When the air-fuel ratio is to be controlled, a final fuel injection amount Ti = Tp * (1 / λt) * (α + αL + COEF) is determined by using the basic fuel injection amount Tp, a target air-fuel ratio λt Air / fuel ratio control correction coefficient α, an air / fuel ratio learning value αL and various coefficients COEF based on the detection signals from the air / fuel ratio sensor 13 calculated, calculated.

If the air / fuel ratio is openly controlled, the air-fuel ratio control correction coefficient α is fixed to 1 (α = 1), for the final Calculate fuel injection quantity Ti.

in the Next, the fuel injection control will be according to a first embodiment described.

As in 2 1, a fuel injection control section in the present embodiment includes an output decision section 21 that has an output to the fuel injector 5 decides, and an air / fuel control section 22 , which is indicated by dashed lines in the drawing.

The issuing decision section 21 decides, in accordance with operating conditions, whether one by the air / fuel ratio control section 22 calculated control correction quantity is to be output to the fuel injection valve. If the controlled variable is not to be output, a lock value (1 when the open control is executed, 0 when the fuel supply is interrupted) is output as a controlled variable.

The air / fuel control section 22 includes a sliding mode control section 221 , a time-out compensator 222 , a plant model identification section 223 , a control gain calculating section 224 , a time-out calculation section 225 , an air / fuel ratio learning section 226 and a different correction amount setting section 227 ,

wobei e(t) eine Eingabe in den Gleitmodus-Steuerabschnitt 221 ist (Ziel-Luft/Kraftstoff-Verhältnis – tatsächliches Luft/Kraftstoff-Verhältnis), K_P eine Linearterm-Linearverstärkung ist, K_D eine Linearterm-Derivativverstärkung ist, K_I eine Adaptivgesetzverstärkung ist, K_N eine nichtlineare Verstärkung ist und σ(t) eine Schaltfunktion ist, wobei σ(t) = S_Pe(t) + S_DΔe(t).The sliding mode control section 221 calculates a control quantity u (t) for a controlled system (between the fuel injection valve 5 and the air / fuel ratio sensor 13 ), ie in other words the controlled variable for the fuel injection valve 5 (the air / fuel control correction coefficient α) in accordance with the following equation (1) by the sliding mode control based on a deviation between the target air / fuel ratio λt and the actual air / fuel ratio λt.

where e (t) is an input to the sliding mode control section 221 is (target air / fuel ratio - actual air / fuel ratio), K _{P is} a linear term linear gain, K _{D is} a linear term derivative gain, K _{I is} an adaptive law gain, K _{N is} a nonlinear gain, and σ (t ) is a switching function, where σ (t) = S _P e (t) + S _D Δe (t).

It should be noted that each control gain in the control gain calculating section described later 224 is calculated.

The time-out compensator 222 serves to perform the time-out compensation control by means of a Smith method, compensating the influence of the time-out (ie, a phase shift of the detected air-fuel ratio) in the controlled system by performing local feedback.

In particular, the time-out compensator calculates 222 who like in 3 shown a plant model 31 without time-out, a plant model 32 with a timeout k and a subtraction section 33 includes a deviation e2 between one on the route model 31 without outage element calculated output prediction (air / fuel ratio) and one on the route model 31 time-out calculated actual output prediction (actual air-fuel ratio) to the deviation e2 to the input side of the sliding mode control section 221 to give.

Then e3 is calculated by the off-time compensator 222 outputted deviation e2 is subtracted from a deviation e1 between the target air-fuel ratio λt and the actual air-fuel ratio λr, and then it enters the sliding mode control section 221 is entered.

The above-mentioned controlled-system model becomes in the controlled-system model identification section described below 223 is identified, and the time-out k becomes in the time-out calculation section also described later 225 calculated.

The plant model identification section 223 identifies the controlled system model for the controlled system directly by means of a transfer function on the basis of the fuel injection quantity (fuel injection signal) and the actual air / fuel ratio (output). In particular, a recursive least squares method (RLS method) is used to perform a recursive calculation of the parameters of the controlled system model.

The control gain calculating section 224 calculates the control gain of the sliding mode control section 221 using the parameter of the law-stretching model identified by the controlled-system model identification section.

In particular, the self-adjusting control is used by means of a pole assignment method to transmit an entire system (in other words, controlled system (between the fuel injection valve) through a control transfer function 5 and the air / fuel ratio sensor 13 ) + Sliding mode control section 221 + Time-out compensator 222 ), the control gain of the sliding mode control section 221 so that one pole of the rule transfer function coincides with a desired pole in terms of response characteristic, excess, stabilization period, etc. (details will be described later).

The time-out calculation section 225 calculates the timeout k contained in the controlled system. The calculation of the time-out k is made, for example, by previously preparing a table showing a relationship between the intake air amount Qa and the time-out k as in FIG 4 and retrieving the table based on the detected intake air amount Qa.

The air / fuel ratio learning section 226 learns a deviation between the controlled variable and a reference value caused by wear or variations of parts of the air / fuel ratio control system. Specifically, a deviation Δα between the reference value (α0 = 1) and a value obtained by weighted averages from a plurality of samples of the controlled variable u (t) as the air-fuel ratio control correction coefficient α is calculated and becomes a predetermined ratio the deviation Δα (<1) is calculated as a learning value UL and updated in a RAM.

The different correction amount setting section 227 sets various correction amounts UK such as a water temperature correction coefficient on the basis of the detected water temperature value.

Then, in accordance with one aspect of the present invention, the air / fuel ratio learning section will be described 226 learned learning value UL and the different correction amount setting section 227 set various correction amounts UK to the control correction amount u (t) ', which from the sliding mode control section 221 the added value is then output as a control input u (t) [= u (t) '+ UL + UK] into the controlled-route model identifying section 223 is entered.

In the following, the calculation of the control gain in the control gain calculating section will be described 224 described in detail.

The Calculation of the control gain using the self-adjusting control by the pole allocation method is performed as follows.

First, a controlled system model G _P (z ^-1 ) is determined, which reproduces the controlled system by the transfer function. Thereafter, a transfer function G _C (z ^-1 ) of the sliding mode control section 221 and a transfer function G _L (z ^-1 ) of the off-time compensator 222 receive.

Then, on the basis of these transfer functions, a rule transfer function W (z ^-1 ) of the entire system is calculated, and the control gain is calculated so that one pole of the rule transfer function becomes a fixed pole.

in the The following describes the definition of the controlled system model.

The controlled system between the fuel injection valve 5 and the air / fuel ratio sensor 13 is exemplified by a quadratic ARX model A (z ^-1 ) as in the following equations (2) and (3) using the off-time calculation section 225 calculated time-out k (≥ 1). A (z -1 ) y (t) = z -k b 0 u (t) + ε (t) (2) A (z -1 ) = 1 + a 1 z -1 + a 2 z -2 (3) where y (t) is a controlled system output (ie, the actual air / fuel ratio), u (t) is a controlled system input value (ie, the fuel injection amount), and ε (t) is random noise.

Then, the transfer function G _P (z ^-1 ) of the controlled-system model can be expressed by the following equation (4). G P (z -1 ) = z -k b 0 / A (z -1 ) (4)

Furthermore, a calculation parameter vector θ (t) and a data vector Ψ (t-k) can be expressed by the following equations (5) and (6). θ (t) = [a 1 (t), a 2 (t), b 0 (T)] T (5) Ψ (t-k) = [-y (t-1), -y (t-2), u (t-k)] T (6)

in the The following is the identification (parameter calculation) of the controlled system model described.

The specified controlled system model becomes in the controlled system model identification section 223 identified.

In particular, a characteristic of the distance model is changed in accordance with operating conditions and process model characteristics such as wear of the process itself, so that the process model by the sequential calculation of input parameters a ₁ (t), a ₂ (t) and an output parameter b ₀ (t) of Equation (5) (by a direct identification) is identified.

Farther is in the present embodiment uses the recursive least squares method (RLS method), to calculate the above parameters, being sequential Parameters are calculated in which the square of an error is between an actual one Value and a calculated value becomes minimal.

wobei

θ ^(t):

Parameterschätzwert (Parametervoraussagewert)

ε(t):

Voraussagefehler (tatsächlicher Wert – Voraussagewert)

P(t):

m·m-Matrix aus Eingabe/Ausgabe (Kovarianzmatrix)

Ψ(t):

Ein-/Ausgabewert (Datenvektor)

λ₁, λ₂:

Vergessenskoeffizient

weiterhin ist ein Anfangswert der Parameterschätzung: θ ^(0) = θ0 und ist ein Anfangswert der Kovarianzmatrix P(0) = α·I, wobei α = 1000 (I gibt die Einheitsmatrix an).A particular calculation is identical to a general weighted and recursive least squares method (RLS method) and is performed by using the following equations (7) through (9) with respect to a time-update equation t = 1, 2, ..., N are calculated.

in which

θ ^ (t):

Parameter estimate (parameter prediction value)

ε (t):

Prediction error (actual value - prediction value)

P (t):

m · m matrix of input / output (covariance matrix)

Ψ (t):

Input / output value (data vector)

λ ₁ , λ ₂ :

forgetting coefficient

Further, an initial value of the parameter estimation is: θ ^ (0) = θ0 and is an initial value of the covariance matrix P (0) = α · I, where α = 1000 (I indicates the unit matrix).

Then, by sequentially calculating the parameters a ₁ (t), a ₂ (t) and b ₀ (t) using the parameter calculation equations (7) to (9), the plant model is identified.

For the forgetting coefficients λ ₁ , λ ₂ , if no forgetting element is present, λ ₁ = λ ₂ = 1, while if a forgetting element is present, λ ₁ = 0.98 and λ ₂ = 1.

Furthermore, an initial value in accordance is set with operating conditions (for example, a ₁ (0) = A1 in the present embodiment, as an initial value θ0 of the parameter calculation value, a ₂ (0) = A2 and b ₀ (0) = B1, by the time period up to the To reduce convergence.

The following is the calculation of a discrete time transfer function of the sliding mode control section 221 described.

The sliding mode control section 221 is made a transfer function in accordance with the following procedure.

wobei e(t) = ω(t) – y(t), e(t) – e(t-1) = Δe(t), sodass die folgende Gleichung (11) aus der Gleichung (10) erhalten wird.

wobei K(z.1) durch die folgende Gleichung (12) widergegeben wird, die zu der Gleichung (13) erweitert wird, um eine Berechnung auf der Basis jeder Steuerverstärkung vorzunehmen. K(z–1) = KP(1 – z–1) + KD(1 – z–1)2 + KISP + KISD(1 – z–1) (12) = (KP + KISP + KISD + KD) – (KP + KISD + 2KD)z–1 + KDz–2 (13) It is assumed that y (t) is a controlled system output (actual air / fuel ratio λr), ω (t) is a target value (target air / fuel ratio λt), and e (t) = ω (t) - y (t), wherein a difference Δu (t) of the control path input u (t) of a sample (in other words, the output from the sliding mode control section 221 ) can be calculated by the following equation (10).

where e (t) = ω (t) -y (t), e (t) -e (t-1) = Δe (t), so that the following equation (11) is obtained from the equation (10).

wherein K (z.1) is represented by the following equation (12) which is extended to the equation (13) to make a calculation on the basis of each control gain. Concentration camp -1 ) = K P (1 - z -1 ) + K D (1 - z -1 ) 2 + K I S P + K I S D (1 - z -1 ) (12) = (K P + K I S P + K I S D + K D ) - (K P + K I S D + 2K D ) z -1 + K D z -2 (13)

Accordingly, from the equation (12), the control-line input u (t) can be expressed by the following equation (14).

Meanwhile, when the calculation is performed such that the nonlinear term is not picked up, the discrete time transfer function G _c (z ^-1 ) of the sliding mode control section 221 are expressed by the following equation (15). G c (z -1 ) = K (z -1 ) / (1 - z -1 ) (15)

The following is the calculation of a discrete time transfer function of the time-out compensator 222 described.

As mentioned before, the time-out compensator uses 222 the Smith method, which compensates for the influence of a time-out element during the execution of the output prediction after the time-out, so that a discrete time-transfer function G _L (z ^-1 ) of the time-out compensator 222 can be calculated by the following equation (16). G L (z -1 ) = z -1 b 0 / A (z -1 ) - z -k b 0 / A (z -1 ) = (z -1 - z -k ) b 0 / A (z -1 ) (16)

It should be noted that z ^-1 b ₀ / A (z ^-1 ) is a no-time output prediction expressed using the plant model, while z ^-k b ₀ / A (z ^-1 ) represents an actual output prediction with a Time out is expressed using the controlled system model.

5 FIG. 12 is a block diagram using the corresponding transfer functions (plant model, sliding mode control section). FIG 21 , Auszeitkompensator) who calculated as described above who the.

in the The following describes a method by which the entire System to a rule transfer function is done.

As mentioned above, the nonlinear term of the sliding mode control section 221 not recorded.

The calculation of a rule transfer function W (z ^-1 ) of the entire system is performed as follows.

First, a control loop of the sliding mode / control section 221 and the time-out compensator 222 taken out to calculate a transfer function from a target (target air / fuel ratio λt) to an output (controlled variable). In 5 may be a transfer function G _CL (z ^-1 ) of the local loop including the sliding mode control section 221 and the time-out compensator 222 are calculated by the following equation (17) on the basis of the equations (15) and (16).

Accordingly, the control transfer function W (z ^-1 ) of the entire system including the local loop of equation (17) and the controlled system can be calculated by the following equation (18).

6 Fig. 10 is a block diagram showing the result of the above equation.

The calculation of the control gain of the sliding mode control section 222 by the pole allocation method is done as follows.

From equation (1), it follows that the characteristic polynomial of the rule transfer function W (z ^-1 ) is the polynomial (1 - z -1 ) A (z -1 ) + z -1 b 0 Concentration camp -1 ) and that this is used in the following equation (19). (1 - z -1 ) A (z -1 ) + z -1 b 0 Concentration camp -1 ) = T (z -1 ) = 1 + t 1 z -1 + t 2 z -2 (19)

It is determined by setting T (z ^-1 ) to the desired pole in terms of response characteristic, Excess, stabilization period, etc., the control gain of the sliding mode control section 221 calculated as follows.

The following equation (20) is obtained from the equation (19).

This results on the basis of equation (13): Concentration camp -1 ) = (K P + K i S P + K i S D + K D ) - (K P + K i S D + 2K D ) z -1 + K D Z -2 ,

By thus setting the switching function linear gain S _P and the switching function derivative gain So to 1 and by setting the linear term linear gain K _P , the adaptive term gain K _I and the linear term derivative gain K _{D of} the linear term as variable parameters the following equation (21) can be obtained.

Then, the following equations (22) to (24) are obtained.

By solving equations (22) to (24) for each K _P , K _I and K _D and expressing a ₁ , a ₂ and b ₀ sequentially through the plant model identification section 223 calculated computation parameters a ₁ (t), a ₂ (t) and b ₀ (t), each gain can be calculated by the following equations (25) to (27), respectively.

Furthermore, for the characteristic polynomial T (z ^-1 ) = 1 + t ₁ z ^-1 + t ₂ z ^-2, the use of the denominator the transfer function are considered when the quadratic, continuous time system G (s) = ω 2 / (S 2 + 2ζω s + ω 2 ) is made discrete by a sampling time Ti, where the attenuation ζ = 0.7 and the natural angular frequency ω = 30.

Then, the sliding mode control section calculates 221 the control variable for the controlled system using the so-called control gain (see equation 13).

As described above, the entire system is expressed by a single transfer function using the control-route model obtained by sequentially calculating parameters, wherein the control gain of the sliding-mode control section 221 for calculating the controlled variable for the controlled system so that the pole of the transfer function coincides with the desired pole in terms of response characteristic, excess, stabilization period, etc. In this way, a good control gain, which corresponds well to the characteristic change of the controlled system can be calculated, so that an accurate air / fuel control can be performed.

Also in the air-fuel ratio control system described above, it is similar advantageous in a general air / fuel ratio control, a deviation of the controlled variable from one To learn reference to wear of the parts over time or the like is due. If no such learning is done, one will be corrected by which should have been made by learning through which System model identification absorbed. Such a controlled system model identification is not on the actual Operating conditions adjusted, with the parameter values to be identified of the controlled system model due to a change in operating conditions changed a lot so that no stable regulation can be carried out.

It is therefore also advantageous in the air / fuel ratio control system described above, the air / fuel ratio learning However, it has been found that the application of air / fuel ratio learning how in the conventional one Procedure causes the following problems. If namely the Operating conditions changed and in the to the identification section of the controlled system model entered data, the learning value to a learning value of a new operating range (i.e., when the learning value of the new operating range is an initial value), the actual air / fuel ratio is on the output side, by the air / fuel ratio sensor is determined, a value representing the learning value while the Controlled variable on the Input side of the fuel injection quantity remains unchanged. That's why the plant model identification was not carried out correctly. This As a result, the tax gain on the basis of the identification of the parameter obtained can not be used can, so it's impossible will get a good air / fuel control power.

The same thing applies to the correction based on the water temperature and the like next to learning. Even if not taken into account by the correction Rule correction size and that taken into account by the correction actual Air / fuel ratio entered be used to identify the controlled system model (parameter calculation), no satisfactory identification can be carried out.

Because, in the present embodiment, the air-fuel ratio learning value UL and the various correction amounts UK are different from those of the sliding mode control section 221 issued and in the plant model identification section 223 control variable u (t) to be input, the control input and control output can be compared under the same conditions to identify the controlled system model or to calculate the parameters.

from that that results satisfactory to the actual Condition adjusted parameters can be obtained to the controlled variable with high To calculate accuracy. Even if the learning value to be used or different correction values due to a change changed in the operating conditions be, the air / fuel ratio control can be stable and with high accuracy become.

in the The following will be a second embodiment described.

7 shows the air / fuel ratio control function of the present embodiment, wherein the air / fuel control section 22 a controlled variable calculation prevention section 228 includes.

The controlled variable calculation prevention section 228 prevents the calculation (update) of the controlled variable by the sliding mode control section 221 that calculates the controlled variable under predetermined operating conditions, particularly when open control is performed with an air-fuel ratio control correction coefficient α fixed at 1 (α = 1) and when the fuel supply is cut off. The satisfaction of such conditions in an open control or interrupted fuel supply is determined, for example, by the drive signal from the fuel injection valve 5 or a flag (fuel cut flag) is checked.

The reason why the calculation of the controlled variable is prevented is that when the calculation of the controlled variable also in a control or regulation (that is, in the sliding mode control section 221 calculated control variable does not become the fuel injection valve 5 is output) or continued at a fuel cut, the integral term (which is calculated on the basis of error amount = target air / fuel ratio - actual air / fuel ratio) is increased in the sliding mode control, and thereafter upon resumption of the Control no corresponding fuel injection control can be performed.

Then, after the open control or the fuel cut is completed, the control (ie, the calculation of the controlled variable by the sliding mode control section 221 ) resumed. In the present embodiment, an initial value previously set in accordance with operating conditions is set to the integral term in the sliding mode control at the time of resumption.

In this way, the integral term in the sliding mode control is reset by the initial value previously set in accordance with operating conditions when the control is resumed, so that a corresponding control quantity to the fuel injection valve 5 can be issued immediately after the resumption of the scheme.

Of the The initial value described above can after the resumption of the scheme continue for one be maintained for a predetermined period of time, the reaction delay after to consider the recovery.

This allows a more suitable controlled variable to the fuel injection valve 5 are output because the calculation of the integral term is not performed during the response delay.

at execution The open control is therefore not provided with a calculation of the controlled variable (or this is prevented), but also in this case a corresponding fuel injection control after the resumption of the scheme can be provided by the previously defined Initial value in accordance with operating conditions on the integral term in the sliding mode control is set when the control is resumed, in which case this initial value for a predetermined period of time is maintained.

Furthermore, as in 7 shown an identification prevention section 229 Preferably, the identification of the controlled-route mode (parameter estimation) during the open control and fuel supply interruption similar to the prevention of the calculation of the controlled variable by the sliding mode control section 221 to prevent.

That is, during the control, the fuel injection by means of the sliding mode control section 221 calculated control variable, while in the open control or fuel supply interruption other than the value by the sliding mode control section 221 calculated controlled variable to the fuel injection valve 5 is issued. Therefore, a controlled system state prediction (plant model identification) that is completely different from that performed during the control can be performed. Under such circumstances, it does not make sense to perform the controlled condition state prediction to calculate the controlled variable because this would lead to false identification results (deterioration of the identification accuracy of the controlled system model).

Around Such deterioration of the identification accuracy (parameter estimation accuracy) prevent the controlled system model identification is prevented, if the regulation is not carried out.

At this time, the calculation of the control gain by the control gain calculating section also becomes 224 not done correctly, so that the calculation of the control gain can be similarly prevented.

The Identification of the controlled system model is resumed when the regulation is resumed (though the calculation the tax gain was prevented, the calculation of the same is also resumed). When resuming the identification, the previously in accordance initial value θ0 set with operating conditions (A1, A2, B1) as the parameter used in the controlled system model.

By doing that is, immediately before the prevention of identification by the initial value θ0 (A1, A2, B1) used parameter value, the identification accuracy after the resumption of identification at a high level be maintained without the change in the control path characteristic taken into account before and after the prevention of identification so that the convergence time is also shortened.

Of the set initial value (parameters A1, A2, B1) is for a predetermined Duration of time after the resumption of identification maintained.

The reason for this is that not only immediately after the resumption of the identification but also for a predetermined period immediately after the resumption of the identification due to the response delay, no air / fuel ratio in accordance with the by the sliding mode control section 221 calculated control variable can be detected, so that it is impossible to obtain a correct identification result, similar to when no control is performed.

As described above, in the present embodiment, during open control and fuel cut, the calculation of the controlled variable by the sliding mode control section 221 also preventing the estimation of the parameter by the plant model identification section 223 is prevented, so that the calculation of an erroneous result can be prevented in advance to perform a corresponding fuel injection control in the resumption of the control and to obtain an accurate control of the air / fuel ratio.

in the Following is a third embodiment described.

8th FIG. 16 shows the air-fuel ratio control function according to the present embodiment, wherein the identification-preventing section included in the second embodiment. FIG 229 in the air-fuel ratio control section 22 is included and a controlled system input / output storage section 23 is provided.

The controlled system input / output storage section 23 stores the control amount (ie, α = 1) and the detected air / fuel ratio during the open control (ie, when the output decision section 21 outputs the value 1 as the control variable).

Similar to the second embodiment, the identification of the controlled-system model during the open control and the fuel-cut by the identification-inhibiting section 229 prevented. However, when the open control is ended and the control model identification and the control are resumed, the control amount and the air / fuel ratio that are in the controlled system input / output storage section 23 are stored as input / output data of the controlled system set.

Even when the control is resumed, the actual air-fuel ratio detected during a period between the resumption and the elapse of the time-out k of the controlled system does not match that through the sliding mode control section 221 calculated control variable, but that during the open control. Thus, when the plant model identification is performed on the basis of such uncorrelated input / output data, the identification accuracy is greatly impaired.

Accordingly, the control amount and the air-fuel ratio of the control included in the controlled-system input / output storage section do not become at the resumption of control but also during the period between the resumption and the elapse of the time-out k of the controlled system 23 stored as input / output data of the controlled system used to identify the controlled system model.

It is possible, the convergence of the controlled system model parameter after the resumption of the Shorten regulation whereby a false identification (parameter estimation) can be prevented.

from that results that even after the resumption of the scheme a good tax gain, the the characteristic change well-balanced, can be calculated at an early stage, so a very accurate air / fuel ratio control carried out can be.

in the Following is a fourth embodiment described.

9 shows the air / fuel ratio control of the present technical teaching, wherein the air / fuel ratio control section 22 a second controlled variable calculation prevention section 230 includes.

The second controlled variable calculation prevention section 230 prevents the setting of a control amount when a control direction (an increasing / decreasing direction of the air-fuel ratio) and a direction of change of the actual air-fuel ratio do not coincide with each other when the time-out is not adjusted.

One by the second controlled variable calculation prevention section 230 performed control is in the flow chart of 10 shown.

In step 1 it is decided whether the control direction agrees with the direction of change of the actual air / fuel ratio.

In particular, in the plant model identification section 223 decided whether the positive / negative sign of the parameter b ₀ (input parameters) of the controlled system input value corresponds to the positive / negative sign of the parameters a ₁ , a ₂ (output parameter) of the controlled system output value. In other words, when the positive / negative sign of the input parameter b ₀ coincides with the positive / negative sign of the output parameters a ₁ , a ₂ , it is decided that the control direction (increasing / decreasing direction of the fuel injection amount) coincides with the changing direction of the actual air / Fuel ratio (a strong / weak direction) coincides. On the other hand, if the positive / negative signs of the parameters do not coincide with each other, it is decided that the control direction does not coincide with the direction of change of the actual air-fuel ratio.

Alternatively, it is decided whether the control gain K ₁ corresponding to the integral term of the switching function σ (t) in the equation for the controlled variable u (t) is calculated from that in the control gain calculating section 224 calculated control gains multiplied, is positive or negative. When the control gain K _{1 is} negative, it is judged that the control direction coincides with the changing direction of the actual air-fuel ratio. On the other hand, if it is positive, it is decided that they do not coincide. The reason for this is that, as shown in the equation (10), when the fuel injection amount is controlled to be increased at a positive change amount Δu (t) of the controlled variable u (t), the switching function σ (t) including e ( t) = target air / fuel ratio - actual air / fuel ratio should take a negative value, the control gain K _{1 is set} to increase the correction of the fuel injection amount to a negative value.

When in step 1 is decided that the control direction and the direction of change of the actual air / fuel ratio do not coincide with each other, the control proceeds to step 2 where the setting of the controlled variable is prevented. In this case, the simplest and most direct method is to set each control gain K _P , K _D , K _I and K _N to 0. As a result, the controlled variable u (t) is equal to 0.

Alternatively, the values of the parameters a ₁ , a ₂ and b _{0 are} each limited. Specifically, the values of the output parameters a ₁ and a _{2 are} reduced (for example, to 0), and the value of the input parameter b _{0 is} increased, so that the control amount u (t) becomes sufficiently small to prevent the setting.

The values of the parameters a ₁ , a ₂ and b _{0 can also be} initialized in order to approximate the control variable to zero.

The determination of the controlled variable is thus prevented when the control direction of the controlled variable (increase or decrease of the control direction of the air / fuel ratio) and the direction of change of the actual air / fuel ratio due to a deviation of the time-out between the fuel injection valve 5 and the air / fuel ratio sensor 14 of the actual value do not agree with each other, so that a control variable in the wrong direction is prevented and only the control is performed in the correct direction. Accordingly, deterioration of the discharge is prevented and the convergence of the air-fuel ratio with the target value is accelerated.

Farther It can be easy to define the controlled variable be prevented by the control gain is set to 0.

Also the determination of the controlled variable by Parameters identified in the wrong direction can be prevented be by the values of for the identification parameters used are either limited or be initialized.

In addition, can based on the positive / negative sign of the input parameter and the while the identification calculated output parameters or on the basis the control gain positive / negative sign simple decide whether the control direction of the scheme with the direction of the actual Air / fuel ratio matches the target air / fuel ratio.

Hereinabove, first to fourth embodiments have been described, but the technical teaching can be implemented so as to include all the structures of these embodiments to obtain all the effects of the various embodiments. 11 shows the air / fuel ratio control according to a fifth embodiment, which combines all the embodiments described above.

Claims (14)

An apparatus for controlling the air-fuel ratio in an internal combustion engine, wherein the apparatus detects an actual air-fuel ratio by means of an air-fuel ratio sensor based on an exhaust condition, by means of a control unit, an air-fuel ratio control signal which injects a control amount based on the actual air-fuel ratio during execution of a control and injects an amount of fuel in accordance with a target air-fuel ratio by means of a fuel injection valve, the fuel injection valve being the air-fuel ratio Control signal receives to control the air / fuel ratio, characterized by: identification means ( 223 ) for calculating parameters of transfer functions, while sequentially identifying a plant model that controls a control path between the fuel injector ( 5 ) and the air / fuel ratio sensor ( 13 ) by the transfer functions, a control quantity setting means for setting the controlled variable of the air / fuel ratio control signal by a sliding mode control on the basis of the parameters of the identified controlled system model, a direction decision means for deciding whether a control direction of the controlled variable and a Change direction of the actual air / fuel ratio coincide with each other or not, and a control amount setting prevention means for preventing the determination of the controlled variable, when the control direction of the controlled variable and the direction of change of the actual air / fuel ratio do not coincide with each other. Device according to claim 1, characterized in that that a tax gain based on the calculated parameters of the controlled system model is calculated, the controlled variable set the sliding mode control using the control gain will and the tax gain is set to zero in order to prevent a determination of the controlled variable. Device according to Claim 1 or 2, characterized that the determination of the controlled variable prevented is determined by the values of parameters in the identification of the Controlled system model are limited. Device according to one of claims 1 to 3, characterized that the determination of the controlled variable prevented is determined by the values of parameters in the identification of the Rule model are initialized. Device according to one of claims 1 to 4, characterized that it is decided that the control direction of the controlled variable and the Direction to the target air / fuel ratio do not match each other, if the positive / negative sign of the input parameter is not with the positive / negative sign of the identification of the controlled system model calculated output parameter. Device according to one of claims 1 to 5, characterized that the tax gain up calculated based on the calculated parameters of the controlled system model is and the controlled variable by the Sliding mode control using the control gain is determined, based on the positive or negative Sign of the control gain It is decided whether the control direction of the controlled variable and the Direction to the target air / fuel ratio match each other or not. Device according to one of claims 1 to 6, characterized that a time-out compensation for eliminating an effect of in off-time using the controlled system model is performed during the identification of the controlled system model. Method for controlling the air / fuel ratio in a combus tion engine, the method based on an air / fuel ratio sensor an exhaust condition determines an actual air / fuel ratio, generates an air / fuel ratio control signal by means of a control unit, the one controlled variable on the Base of the actual Air / fuel ratio while the implementation contains a regulation, and by means of a fuel injection valve, an amount of fuel in accordance injected with a target air / fuel ratio, wherein the Fuel injection valve, the air / fuel ratio control signal receives about the air / fuel ratio to control characterized by the following steps: To calculate parameters of transfer functions, while sequentially a controlled system model is identified, which is a Control path between the fuel injection valve and the air / fuel ratio sensor through the transfer functions reproduces, Defining the controlled variable of the air / fuel ratio control signal based on the actual air / fuel ratio while the implementation a control by a sliding mode control on the basis of Parameters of the identified controlled system model, Decide, whether a control direction of the controlled variable and a direction of change of the actual Air / fuel ratio agree with each other or not, and Prevent the determination of the controlled variable, if the control direction of the controlled variable and the direction of change of the actual Air / fuel ratio do not agree with each other. Method according to claim 8, characterized in that that the tax gain based on the calculated parameters of the controlled system model is calculated, the controlled variable set the sliding mode control using the control gain will and the tax gain is set to zero to prevent the determination of the controlled variable. Method according to claim 8 or 9, characterized that the determination of the controlled variable prevented is determined by the values of parameters in the identification of the Controlled system model are limited. Method according to one of claims 8 to 10, characterized that the determination of the controlled variable prevented is determined by the values of parameters in the identification of the Rule model are initialized. Method according to one of claims 8 to 11, characterized that it is decided that the control direction of the controlled variable and the Direction to the target air / fuel ratio do not match each other, if the positive / negative sign of the input parameter is not with the positive / negative sign of the identification of the controlled system model calculated output parameter. Method according to one of claims 8 to 12, characterized that the tax gain up calculated based on the calculated parameters of the controlled system model is and the controlled variable by the Sliding mode control using the control gain is determined, based on the positive or negative Sign of the control gain It is decided whether the control direction of the controlled variable and the Direction to the target air / fuel ratio match each other or not. Method according to one of claims 8 to 13, characterized that a time-out compensation for eliminating an effect of in off-time using the controlled system model is performed during the identification of the controlled system model.