JPS597753A - Simultaneous control for idle revolution speed and air-fuel ratio in internal combustion engine - Google Patents

Abstract

PURPOSE:To simultaneously control the idle revolution speed and the air-fuel ratio by recognizing an engine as a dynamic system and using a state-variable controlling method, estimating the dynamic behaviour of an engine according to the state variable which prescribes the interanl state. CONSTITUTION:A state observation equipement 15 calculates the estimated value-X of the amount of the state variable X which represents the internal state of an engine 13. The increment deltaPA(.) within a range in which the linear approximation from the standard set value (PA)a of the pulse width of a control solenoid 3 which constitues a control input is established and the increment deltaPF(.) within a range in whcih the linear approximation from the standard set value (PF)a of the fuel injection pulse width is established are determined by using a state variable - X(.) and the deviation between an aimed revolution speed Nr and an actual revolution speed N(.) at present, namely SA=Nr-N(.) and the deviation between an aimed air-fuel ratio A/F and an air-fuel ratio A/F(.) at present which is estimated from the output signal of an O2 sensor 12. Then, the optimum regulator control for the idle revolution speed N and A/F is performed.

Description

Detailed Description of the Invention (Technical Field) The present invention relates to a method for simultaneously controlling the rotational speed and air-fuel ratio of an internal combustion engine during idling. Differently, the engine is considered as a dynamic system by considering the internal state of the engine, and the engine's input variables are determined while estimating the engine's dynamic behavior using the state variables that define the internal state. This invention relates to a method for simultaneously controlling idle rotation speed and air-fuel ratio using variable control techniques.

(Prior Art) As a conventional method for controlling idle rotation speed in an internal combustion engine, there is a method as shown in FIG. 1, for example. The AAC valve 1 for idle speed control changes the lift amount by controlling the control solenoid 3 of the VCM valve 2, and the amount of bypass air passing through the bypass 5 of the throttle valve 4 changes. Idle rotation speed is controlled.

When the control unit 6 detects that the engine is in the idle state based on the idle (DLE) signal from the throttle valve switch 7, the neutral (NEUT) signal from the neutral switch 8, the vehicle speed (VSP) signal from the vehicle speed sensor 9, etc. A basic target value of the idle rotation speed is calculated by a one-dimensional table lookup according to the cooling water temperature ('1'W) detected by the water temperature sensor 10. And 1 air conditioner by near consuinory (A, /C) (l,
Neutral (NEUT) signal, battery voltage (■,)
The control solenoid is operated so that the deviation SA between the engine's actual idle rotational speed N and its target value Nr becomes small with respect to the idle rotational speed target value N, which is finally calculated by making corrections according to signals, etc. 3 as proportional, integral (P I )
The data control is performed to perform feedback control to a target rotational speed of 111'J.

The above control method is shown in a flowchart in Figure 2.

On the other hand, the air-fuel ratio (mixture ratio of fuel and air) is controlled by first determining the basic fuel supply amount '11' from the engine rotational speed N and the intake air flow rate Q. ．． Find it using I', -K Q/N (1 or a constant). Then, based on the output value of the 02 sensor 12, which outputs a signal according to the air-fuel ratio according to the oxygen concentration of the exhaust mixture, the correction factor α for the basic fuel supply amount I11.. is 111 controlled. Accordingly, the actual air-fuel ratio A/, 1.'' is feedback-controlled to the target air-fuel ratio (A/I.'').

However, in such conventional idle rotation speed and air-fuel ratio control methods, idle rotation speed control by manipulating the bypass air amount and air-fuel ratio control by manipulating the fuel supply amount are independent of each other. On the other hand, if the fuel supply amount is increased or decreased to perform air-fuel ratio control, the idle rotation speed will change. Therefore, if the bypass air amount is increased or decreased to perform idle rotation control, This time, the air-fuel ratio changes, and although they are controlled independently, they influence each other, making it difficult to perform stable control of the idle speed and air-fuel ratio.

(Object of the Invention) The present invention has been made in view of these conventional problems, and an object of the present invention is to optimally and stably control the idle rotational speed and the air-fuel ratio at the same time.

(Structure and operation of the invention) Therefore, the present invention provides control inputs that include the amount of air (or equivalent amount) or the amount of fuel supply (or equivalent amount), as well as the ignition timing or the amount of exhaust gas recirculation (or equivalent amount). The engine is characterized by multivariable control using control inputs and control outputs, based on the dynamics of the engine whose control outputs are idle speed, dust, and air-fuel ratio.

Hereinafter, one embodiment of the present invention will be described based on the drawings.

FIG. 3 shows the configuration of an embodiment of the present invention. In the figure, 13 is an engine to be controlled, and the control input is a drive pulse for the control solenoid 3 of the VCM valve 2 that adjusts the amount of bypass air at idle. The width P is the fuel injection pulse width PF that drives the fuel injection valve 14, and the control output is the air-fuel ratio A estimated from the engine rotation speed N and the output value of the 02 sensor 12.
, / Take F.

15 stores a dynamic model of the engine 13 to be controlled, and stores the above four control input/output information P, ,
l) It is a state observer (observer) that estimates the dynamic internal state of the engine from F, N, and A/F, and it is a state variable quantity X (for example, six quantities x,
+ X2 + x3 + X4 + X51 (vector representation of X6) is calculated.

The state observer 15 simulates the engine to be controlled, and the dynamic internal state is expressed as a state variable x (
It is represented by n-th order vectors x1 to Xn).

Specifically, the state variables representing the internal state of the engine 13 that is the controlled object include, for example, the absolute pressure of the intake manifold, the suction negative pressure, the amount of air actually taken into the cylinder, the dynamic behavior of combustion, the engine torque, etc. Can be mentioned. If these values can be detected by a sensor, the detected values can be used to understand the dynamic behavior and used for control, thereby allowing more precise control. However, at present, there are not many practical sensors that can detect these values. Therefore, the internal state of the engine is represented by a state variable X, but the state variable X does not need to correspond to various physical quantities representing the actual internal state, and the engine as a whole is simulated. Degree 11 of state variable X
The larger n is, the more accurate the simulation becomes.
On the other hand, calculation becomes complicated. Therefore, a reduced-dimensional approximation model is used, and approximation errors or errors due to individual engine differences are absorbed by integral operation. In this invention, 2 man power 2
In the case of output, approximately n = 6 is appropriate.

In Fig. 3, 16 is an integral operation and gain block (controller), which is used to set the specified target value N of the engine rotation speed,
and the actual value N, the specified air-fuel ratio is A1 [4 (Izumi 11fi (8/1), and the actual value A/r
', and the state observation device 1
From the state variable X calculated in step 5, calculate the values of the two manual forces PA and PF (see Figure 5).

Next, explain the action.

The engine 13 to be controlled is a two-man power, two-output system, and from the linearly approximated transfer function matrix T (zl) obtained around a certain reference setting value of the rotation synchronized sample value system between the input and output, the controlled object 1 : TiJ function is to estimate the dynamic internal state of
The transfer function matrix T(zl) of the controlled object 13 is determined experimentally and becomes as follows. However, Z indicates the 2-transformation of the sample value of the input/output signal, and T+(zl and I"2(z) are, for example, 2 The second-order transfer functions, ']'3(Z) and 'I'4('') are 201st-order transfer functions.

Input, output and transfer function 'r+(z)~l114(Z
A model structure of the controlled object (engine) 13 showing the relationship of l is shown in FIG. However, the input and output uses deviations δPA, δPF, δN, and δ(A/F) from the reference setting values, respectively.

This transfer function matrix T(zl) is expressed by the state observer 1 as follows.
5 can be configured.

First, a state variable model x(nl =Ax(n-1) + Bu(n-1) that describes the dynamic behavior of the engine from T(zl)
(2)y(n-1) = Cx(n-1)
(3) is derived. Here, (n) in parentheses of the capacity represents the current time, and t(n-1) represents the previous sample time.

u(n-1) is a control input vector, which represents the perturbation within a range where a linear approximation from a certain standard setting value holds. The injection pulse width δPF (n-1) is used as an element. In other words, y(n-1,) is a control output vector, which, like the control input vector, is a certain reference rotational speed Na (for example, 65
δN(n-1) representing the perturbation from the reference air-fuel ratio (Al1(゛)a) and δ representing the perturbation from the reference air-fuel ratio (Al1(゛)a)
(Al1.1)'(n-1) is an element. That is,
X(・) is the state variable vector, and the matrix A, I3
, C is a constant matrix determined from the coefficients of the transfer function matrix 'i''(z).

Here, a state observation device with the following algorithm is constructed.

x(nl-(A-GC)x(n-1) +Bu(n-1
)+Gy(n-1) (6) Here, is an arbitrarily given matrix, and X(・) is the internal state variable X(・) of the engine 13.
0) is an estimated value. Transformed from equations (2), (3), and (6), [x(nl-X(n))-(A-toC)[:X(n-1
)-x(n 1)l) (becomes a force, matrix (A-G
C) 0) If we choose G so that the eigenvalue is within the unit circle, then x (nl −) X (nl
(8), and the internal state variable t
・) and the output y(・), you can estimate 1-. It is also possible to appropriately select the matrix G and make all the eigenvalues of the matrix (A-GC) zero, in which case the state observer 15 becomes a finitely stable state observer.

Deviation 5 between the state variable X (・) estimated in this way, the target rotation speed N, and the current actual rotation speed N (・)
Information on A-(N, -N(・)) and target air-fuel ratio (A/F
), and the current actual air-fuel ratio (A/P > (・) estimated from the output signal of the 02 sensor 12 5B = ((
Using the information of A/F), -(A/F)(・)), the reference setting value (
PA) Increase amount δ within the range where linear approximation from a holds true
PA (・) and standard setting value (PF) of fuel injection pulse width
Increase amount δPF within the range where linear approximation from a holds true (
・) is determined, and engine idle speed N and air-fuel ratio A/
Perform optimal regulator control of F.

Regulator control is constant value control that controls the idle rotation speed N to match the target rotation speed N, which is a constant value, and the air-fuel ratio A/P to match the target air-fuel ratio (A/F)r, which is a constant value. means. In the present invention, since the experimentally obtained model is a low-dimensional approximate model as described above, 1 (integral) operation is added to absorb the approximation error. Performs optimal regulator control including operation.

As mentioned above, the engine to be controlled by this invention is a two-man power, two-output system, which is optimally controlled by the requisite regulator. However, the optimal regulator control algorithm for a general multivariable system is as follows. For example, it is explained in "Linear/Stem Control Theory" by Katsuhisa Furuta (1977), Shokodo and others, so detailed explanation will be omitted here. Describing only the results, now δu(nl = u(n) −u (n-1)
(9) δy(n) = y(Ill-y (n-
1) (10) and the evaluation function J is as follows. Here, Q and R are weight parameter matrices, and t indicates transposition. 1 (is the number of samples with 0 at the start of control, the first term on the right side of equation (11) is the square of equation (10), and the second term is the square of equation (9) (Q, 1< ) are respectively expressed as an angular matrix.Also, the second term of equation 01) is expressed as (9)
The quadratic form of the difference in control input is used as shown in the equation, but this is because one (integral) operation is added as shown in FIG.

This is the optimal control input that minimizes the evaluation function J of equation (11). In equation (12), if -t--1-t-- is set as =-(R+BPB)BPA (13), K is the optimal gain matrix. It is also a solution of the Riccati equation (12).

(The meaning of the evaluation function J in Equation 111 is that while constraining the movement of the control human power U (・), the target value N of the idle rotation speed N, which is the control output y (・), and the deviation SA (rotation fluctuation) of the idle speed N, which is the control output y (・), are It is intended to minimize the deviation S B of the air-fuel ratio A/F from the target value (A/F), and the weighting of this constraint can be changed using the weighting parameter matrices Q and R. Select Q and R, use a dynamic model (state variable model) of the engine at idle, and store the optimal gain matrix K of formula 03), which is calculated using P obtained by solving formula 06), in the microconbeater. Then, the integral value of the deviation between the target value N of the idle rotation speed and the actual value N, and the target value of the air-fuel ratio (A
/Ii'') The integral value of the deviation between r and the actual 1 [(VF) and the estimated state variable x (k) can be easily determined by the equation (1). Also, as mentioned above, in order to obtain the estimated value x (k) of the dynamic state variable of the engine, the matrices A, B, C,
Store the value of G in the micro converter, and (6)
It can be calculated using the formula.

Note that the air-fuel ratio deviation SB from the output signal of the 0□ sensor 12
The method for estimating is as follows.

The 02 sensor 12 outputs an on signal b3 on the rich side of the fuel and an off signal b3 on the lean side of the stoichiometric air-fuel ratio. The output signal of the 02 sensor 12 shown in FIG. 6 is observed at each control period. For example, the first period (
0 to 1), measure the on time and off time, and measure the on (lynch) signal as (-1-1) and the off (lean) signal as (-).
8 B = -t, + t2-13+ t4
The value of SB obtained from the surface may be used as an amount representing how much the air-fuel ratio deviates from the target value (A/F) within the control cycle.

FIG. 7 shows the procedure for simultaneous control of the idle rotation speed and air-fuel ratio. To explain the procedure, in step 30, the target value N of the idle rotation speed is determined based on the on/off state of the air conditioner, the water temperature TwO value, etc.

is determined, and the deviation SA between this target value Nr and the actual value N is calculated by
do. In step 31, the target value of the air-fuel ratio (A
/F”), and determine this target value (A/F) and actual value (
Calculate the deviation SB from A/F). In step 32,
The rotation speed deviation SA from the start of control to the previous cycle is added, and the result is transferred to a register called TJNI. In step 33, the air-fuel ratio deviation S I'3 from the start of control to the previous cycle is added, and the result is 1) U
Move to register N2.

In step 34, a reference set value N of the actual value N of the rotational speed is determined.
In step 35, the deviation from the actual value A/F of the air-fuel ratio (A/1
8゛) Calculate each deviation from a. Step 3
6, the state variables x1 to X representing the dynamic internal state of the engine estimated in the previous control cycle, the calculated control input values δPA and δPF, and the control output values δN, δ<A/p> is weighted and added to calculate each state variable amount x, ~X, H1. However, the matrix of equation 6) (
A-GC) is an example of forming a finitely settled observer in the form.

Note that (A, B, C) use observable canonical forms.

In step 37, dynamic internal state variables x1 to X6 of the engine estimated in the previous control cycle and 1) an element kI for the optimal gain for UNI and DUN2 are calculated.

Multiply and add the standard setting value (PA)a and (PF)
Calculate how much the control input value should be increased for a.

The coefficients b 131 g 131 k s 3, etc. in FIG. 7 are determined in advance and stored in a microcomputer or the like.

(Effects of the Invention) As described above, according to the present invention, the drive pulse width PA and fuel injection pulse width PF of the control solenoid that define the air amount that are the control input, and the idle rotation speed N that is the control output and the air-fuel ratio A/ detected by the 02 sensor
Since the configuration performs multivariable control based on a dynamic model between You can get the effect that you can.

In the above-described embodiment, the pulse width PA of the control solenoid that defines the air amount and the fuel injection pulse width PF are used as control inputs, but the ignition timing or Eqlt (exhaust recirculation)! By adding i' as a control input, it is possible to control the rotational speed N and the air-fuel ratio A/'F, which are control outputs, more accurately, simultaneously, and optimally.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an idle rotation speed control device and an air-fuel ratio control device in a conventional internal combustion engine, FIG. 2 is a flowchart showing a conventional idle rotation speed control method, and FIG. 3 is an idle l111 diagram in an internal combustion engine according to the present invention. A configuration diagram of a control device that realizes a method for simultaneously controlling rotation speed and air-fuel ratio,
Fig. 4 is a block diagram showing the relationship between the control input/output and engine in Fig. 3, Fig. 5 is a diagram showing details of the gain block during integration in Fig. 3, Fig. 6 is an output waveform diagram of the 02 sensor, FIG. 7 is a flowchart illustrating the control method 11 according to the present invention. ■...AAC valve, 2...V(, M valve, 3...control solenoid, 4...throttle valve, 5...
Bypass, 7... Throttle valve switch, 8
...Neutral switch, 10...Water temperature sensor, 11...Air conditioner switch, 12...02 sensor, 13.
... Internal combustion engine (controlled object), 14 ... Fuel injection valve, 15 ... Condition observation device, 16 ...
...Integral tensile gain block, Nr...Target value of idle rotation speed, N...Actual value of idle rotation speed, Na...Reference setting value of idle rotation speed,
SA ・Difference between target value and actual value of idle rotation speed, (A/F) ・・Target value of air-fuel ratio, A, /F ・・・・Actual value of air-fuel ratio, (A/F) a
...Standard set value of air-fuel ratio, 8B...Difference between target value and actual value of air-fuel ratio, 8...Pulse width of control solenoid that specifies bypass air amount, PF...Fuel supply amount Specified fuel injection pulse width, X
l...For state variables, Xl...Estimation of state variables Patent applicant] San Jidosha Co., Ltd. patent application representative Konjinben I11! ,, J: Megumi Yamamoto - Procedural amendment (spontaneous) September 1980, Japan Patent Office Commissioner Kazuo Wakasugi 1, Indication of the case 1982 Patent Application No. 116939 2, Name of the invention Internal combustion engine Simultaneous Control of Idle Speed and Air-Fuel Ratio Act 3, Relationship with the Case of the Person Who Makes the Amendment Applicant's Name (399) Delete Nissan Motor Co., Ltd.
-2 (2) "(See Figure 5)." on page 8, line 4 of the specification is replaced with "(See Figure 5)."
The state observer 15, integral operation, and gain block 16 constitute a controller. ” he corrected. (3) [State variable amount X, ~ x
Correct aJ to [state variable amount X1 to x''l. (4) Delete 1-previous control cycle on page 17, line 3 of the specification. (5) Figure 7 of the drawings will be amended as shown in the attached sheet. ↓

Claims (1)

[Claims] During idle operation of the internal combustion engine, the deviation SA between the target value N of the idle rotation speed and the actual value N, and the target value of the air-fuel ratio <
A, /F) Based on the deviation SB between r and the actual value A/F',
two control inputs for or equivalent to the amount of air supplied to the internal combustion engine and an amount PF or equivalent to the amount of fuel supplied to the internal combustion engine; alternatively, the two control inputs are further provided with an ignition timing or an amount of exhaust gas recirculation; Alternatively, in a method of simultaneously controlling the idle rotation speed N and the air-fuel ratio A/F by determining the value of the control input by adding a corresponding amount, the control input is determined based on the dynamic model of the internal combustion engine stored in the controller. From the rotational speed N and the air-fuel ratio A/F, which are the control output values, a state variable quantity X of an appropriate order representative of the dynamic internal state of the internal combustion engine, (1=1127...n) is determined. is estimated, and the integral value of the estimated state variable quantity X, (i = 1, 2...), the deviation SA of the rotational speed, and the deviation S of the air-fuel ratio is calculated.
A method for simultaneously controlling an idle rotation speed and an air-fuel ratio in an internal combustion engine, characterized in that the control input value is determined from an integral value of B.