JPS59145338A - Control method of idling speed for internal-combustion engine - Google Patents

Abstract

PURPOSE:To aim at a distinct improvement in antistallingness, by discriminating an idling speed with a ratio between an idle switch and a car speed and an engine speed. CONSTITUTION:A something modellizing the dynamic characteristics of an internal-combustion engine 12, an actuator and a sensor is stored in a controller, while a combination of a bypass air quantity PA, ignition timing IT, a fuel feed quantity and an exhaust reflux quantity is set down to the control input and also an idling speed is set down to the control input whereby a state variable representing an inner state is estimated from the input and output of control. Then, using an integral value of a deviation SA between a desired value Nr and an actual value N of the idling speed, a control input valve is determined and the idling speed of the internal-combustion engine 12 is feedback-controlled to meet the desired value, through which a judgement for whether the idling speed is right or wrong is attained with a ratio between a throttle valve switch and a car speed plus an engine speed. Thus, an antistallingness at high-speed driving is improved.

Description

Detailed Description of the Invention (Technical Field) The present invention relates to a method for controlling the rotational speed of an internal combustion engine during idling, and more specifically, unlike conventional PID (proportional integral derivative) control, Considering the internal state of the engine, we view the institution as a dynamic system,
The present invention relates to a method of controlling idle rotation speed using a state variable control technique that determines engine input variables while estimating the dynamic behavior of the engine using state variables that define the internal state.

(Prior art) As a conventional method for controlling the idle rotation speed of an internal combustion engine,
For example, there is one shown in FIG.

In FIG. 1, the lift amount of the AAC valve 1 for idle rotational speed control is changed by duty-controlling the drive pulse width PA of the control solenoid 3 of the VCM valve 2, and the amount of lift of the throttle valve 4 is changed; By changing the amount of bypass air passing through the air path 5, the idle rotation speed is controlled.

The control unit 6 controls the idle (I) speed by controlling the throttle valve switch (also called idle rotation speed) 7.
DLE) signal, 211 tral (NEUT) signal from the neutral switch 8, vehicle speed (VS
, P) When it is detected that the engine is in an idle state by a signal etc., the cooling water temperature (Tw
) Calculate the basic target value of the idle rotation speed by looking up a one-dimensional table according to K. Then, the target idle rotation speed is finally calculated by correcting the air conditioner switch 11 according to the air conditioner (A/C) M number, the 211 tral (NEUT) signal, the battery voltage (VB) signal, etc. With respect to the value Nr, the drive pulse width P^ of the control solenoid 3 is controlled by proportional-integral (PI) duty so that the deviation SA between the actual idle rotation speed N of the engine and its target value Nr becomes small. Feedback control is performed to the target idle rotation speed Nr.

FIG. 2 shows a flowchart of the above control method.

However, such conventional idle speed control methods for internal combustion engines do not perform PI control that effectively uses the dynamic characteristics of the engine, actuators, and sensors (and furthermore, the control method PI control is not suitable for controlling multi-input/output systems. When the engine exhibits dynamic behavior, such as immediately after a motor is applied, there is a problem of poor control followability, or transient response.In addition, it is necessary to increase the degree of freedom in control by adding other control inputs to improve controllability. When doing so, there was a problem in that it was difficult to apply the PI control method.

In particular, if the determination of whether or not to perform idle speed control is made based on the neutral switch 8, throttle valve switch 7, and vehicle speed, it is easy to stall the engine when the gear is set to 211 tral at high speed (and the 211 tral Even when excluding the judgment in 8, there was a problem in that the engine was likely to stall if the engine brake was used to decelerate and the clutch was released.

(Object of the Invention) The present invention has been made by focusing on the conventional problems as described above. It optimizes the control followability, that is, the transient response when the engine exhibits dynamic behavior, such as immediately after engine application, and also increases the degree of control freedom by adding a large number of control input variables, making it easy to improve controllability. The purpose of this is to perform more stable idle rotation speed control. In particular, it is an object of the present invention to appropriately determine whether or not to perform idle rotational speed control, thereby increasing stall resistance when a gear is inserted or removed during high-speed operation or during deceleration by engine braking.

(Structure of the Invention) Therefore, the present invention stores models of the dynamic characteristics of the internal combustion engine, actuators, and sensors in a controller consisting of a microcomputer, etc. or an equivalent amount and an exhaust gas recirculation (EGR) amount or an equivalent amount, or any combination of two or more of them as a control input, and the idle rotation speed as a control output method, and the control input and the control output. From this, we estimate the state variable quantity that substitutes for the internal state of the internal combustion engine, etc., which is a dynamic model,
The control input value is determined using the estimated value and the integral value of the deviation between the target value and the actual value of the idle rotation speed, and the idle rotation speed of the internal combustion engine is subjected to feedbank control to the target value.

This control method uses a multivariable control method that comprehensively controls a large number of input and output variables in place of the conventional general PID control.

Particularly, the present invention is characterized in that the determination as to whether or not to perform idle rotational speed control is made by paying attention to the throttle valve blink and the ratio between the vehicle speed and the engine rotational speed.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

FIG. 3 is a block diagram of an apparatus for implementing an embodiment of the method for controlling the idle rotation speed of an internal combustion engine according to the present invention.

In the figure, reference numeral 12 denotes an internal combustion engine to be controlled, which performs not only idle rotational speed control but also fuel injection control including air-fuel ratio feedback control.

When the control output of the controlled object 12 is the idle rotation speed, the control input may be any one of the air amount, ignition timing, fuel supply amount, and exhaust gas recirculation lid, or any combination of two or more of them. obtain.

In this embodiment, the two control inputs are the pulse width PA (that is, the amount corresponding to the amount of bypass air) that drives the control solenoid 3 (Fig. 1) of the VCM valve 2 for adjusting the amount of bypass air at idle; Take the ignition timing IT.

The control output is the idle rotation speed N, and is an output.

13 stores the dynamics of the internal combustion engine 12 which is the controlled object, and stores the above three control input/output information PA,
It is a state observer that estimates the dynamic internal state of the engine 12 from IT and N, and the state variable quantity x (=x1.1=1.2°...l”o
For example, the estimated value x (=Xl, ■=1.2..., n
).

The state observer 13 simulates the engine 12 that is the object of control, and the dynamic internal state is represented by a state variable ix. Specifically, state variables representing the internal state of the engine 12 to be controlled include, for example, intake manifold supply pressure, suction negative pressure, amount of air actually taken into the cylinder, dynamic behavior of combustion, and engine torque. etc. If these values can be detected by a sensor, dynamic behavior can be grasped by using the detected values, and control can be performed more precisely. However, at present there are not many practical sensors that can detect these values. Therefore, the internal state of the engine 12 is represented by the state variable quantity X, but the state variable quantity X does not need to correspond to various physical quantities representing the actual internal state (the engine 12 as a whole is simulated. As for the order n of the state variable quantity X, the larger n is, the more accurate the simulation becomes, but the computation becomes more complicated. Therefore, a low-dimensional approximation is used as a model, and errors due to approximation errors or individual engine differences are avoided. is absorbed by integral (I) operation.In the case of two people and one output in this invention, n =
A value of about 4 is appropriate.

In Fig. 3, 14 is an integral operation and gain block,
As shown in detail in FIG. The values of the two control inputs PA and IT are calculated from the following.A controller is constituted by the state observer 13, integral operation, and gain block 14 described below.

Next, the action will be explained.

The engine 12 to be controlled is a two-man power, one-output system, and the transfer function matrix T (z) is a line-shaped approximation obtained near a certain reference setting value of the rotation synchronized sample value system between the input and output.
From this, it is possible to estimate the dynamic internal state of the engine 12. As one method, the state observation device 13
There is. Under operating conditions near idle speed, engine 12
The transfer function matrix T(z) of T(z) is found experimentally, and becomes the following. However, 2 indicates 2-conversion of the sample value of the input/output signal, and TI(Z) and T2(zl are, for example, 202nd-order transfer functions).

FIG. 5 shows a model structure of the engine 12 showing the relationship between input, output, and transfer functions T+(z) and T2(Z). however,
The input and output are each deviation from the reference setting value δPA + δIT
.

δN is used.

From this transfer function matrix T(zl), the state observer 13 can be configured as follows.

First, from T(z), a state variable model x(n) −Ax(n-1) 10Bu(n-1) describing the dynamic behavior of the engine 12 is created.
(21y(n-1)=Cx(n-1)
(31 is derived (.Here, n in the parentheses of the capacity represents the current time, n-1 represents the previous sample time.
1) is a control input vector, which includes the driving pulse width δPA (nl) of the control solenoid 3 (Fig. 1) and the ignition timing δIT, which represent the perturbation within a range where linear approximation from a certain reference setting value holds. do. That is, also y(n-1
) is a control output, which, like the control input vector, has an element of δN(n-1) representing a perturbation from a certain reference rotational speed Na (for example, 650 rpm).

That is, y (n-1) = δN (n-1) (51 .

Here, we configure a state observer with the following algorithm.

x(n)-(A-GC)x(n-1)+Bu(n-1)
+Gy(n-1) (6) Here, G is an arbitrarily given matrix, and X(・) is the internal state variable X(・
) is the estimated value. (2) (31 Transforming from equation (6), (x(n)-x(nl)=(A-GC)[x(n-1)
-x(n-1)] f force, matrix (A-GC)
If we choose G so that the eigenvalue of is within the unit circle, then n→thick, x(0)→X(n) (8)
Therefore, the internal state variable quantity x(n) can be estimated from the input U(·) and the output y(·). 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 13 becomes a finitely stable state observer.

Using the state variable amount X(・) estimated in this way and the information of the deviation 5A=(N, -N(・)) between the target rotational speed Nr and the current actual rotational speed N(・), , the reference setting value (P
A) Increase amount δP within the range where linear approximation from &
Determine the amount of increase δIT(・) within the range where linear approximation holds from A(・) and the reference setting value of ignition timing ■Ta,
Optimal regulator control of engine idle speed N is performed. Regulator control means constant value control that controls the idle rotation speed N to match the target rotation speed Nr, which is a constant value.

In this invention, since the experimentally obtained model is a reduced-dimensional approximate model as described above, an integral (I) operation is added to absorb the approximation error. Now, perform optimal regulator control including integral operation.

As mentioned above, the Ichinoseki that is the control target of this invention is a two-man power output system, which is optimally controlled by a regulator, but the optimal regulator control algorithm for a general multivariable system is, for example, Written by Katsuhisa Yoshida “
Since it is explained in "Linear System Control Theory" (1972) by Shokodo et al., detailed explanation will be omitted here. Describing only the results, now δu(n)=u(n)-u(n-1) (
9) δe fn) = Nr N (n)
QO), and the evaluation function J is J= Σ[δe(k12+δu ShuR!3u(k)]'
(I I) Let k=0. Here, R is a weight parameter matrix and [denotes transposition. If k is the number of samples with the control start time being 0, and R is a diagonal matrix, the second term on the right side of equation (11) represents the square of equation (9). Furthermore, the second term on the right side of equation 00 is a quadratic form of the difference in control inputs as shown in equation (9), but this is because an integral action is added as shown in FIG.

Control human power u (kl is as follows. In formula 02, K= - (R 1 B PB) B PA
(13), K is the optimal gain matrix.

Also, (formula 121, P is This is the solution of the Riccati equation.

The meaning of the evaluation function J in equation (11) is to limit the deviation SA (rotation fluctuation) of the idle rotation speed N, which is the control output y (・), from the target value Nr while constraining the movement of the control human power U (・). The weighting of the constraints can be varied with the weight parameter matrix R. Therefore,
Select an appropriate R, use a dynamic model (state variable model) of the engine at idle, and solve equation (16).P
The optimum gain matrix K of formula a'5 calculated using
From the integral value of the deviation SA between r and the actual value N and the estimated state variable quantity x(k), the optimal control input value u is determined by formula 02.
(k) can be easily determined. Further, as mentioned above, in order to obtain the estimated value x(k) of the dynamic state variable quantity of the engine 12, the values of B, C, and G are stored in the matrix in the microconbeater, and (6) It can be calculated using the formula.

In such an idle rotation speed control method for an internal combustion engine, as described above, in particular, the determination of whether or not to perform idle rotation speed control (idle determination) is performed using the conventional 211 tral switch 8 and throttle valve switch. If this is done at the engine brake and vehicle speed, there is a problem that the engine is likely to stall if the gear is set to 211 tral during high speed rotation. Therefore, control is performed in the direction of reducing the amount of bypass air while the actual engine rotational speed N is higher than the target rotational speed Nr during deceleration. If you release the clutch in this condition,
There is a problem that the engine speed decreases and the engine stalls.

Therefore, in the present invention, the idle determination is not performed using the neutral switch 8, but is performed by paying attention to the throttle valve switch 7 and the ratio between the vehicle speed and the engine rotation speed.

FIG. 6 shows the procedure of the above idle rotation speed control. To explain the procedure, in step (9), the target value Nr of the idle rotation speed is determined based on the on/off state of the air conditioner, the cooling water temperature TrwO value, etc. Stenobu 31
In step 3, it is determined whether the throttle valve switch 7 is on, and if it is not on, the process returns, and if it is on, the process proceeds to step 32.

In step 32, it is determined whether the clutch is engaged based on the ratio of the vehicle speed and the engine rotational speed. If it is engaged, the process returns; if it is not engaged, step 33 is carried out.
Proceed to. In step 33, it is determined whether the idle rotation speed control is entered for the first time, and if it is the first time, the state variable quantity
Give initial values to x2+ x3+ x4 and DUN,
Proceed to step 39.

If it is determined in step 33 that this is not the first time that idle rotational speed control has been applied, the step hub 35 calculates the difference SA between the target value Nr and the actual value N of the idle rotational speed. In step 36, the rotational speed deviation SA from the start of control to the previous cycle is added, and the result is transferred to a register called DUN. In step 37, the deviation δN of the actual value N of the rotational speed from the standard set value Na (for example, 650 rpm) is determined.
Calculate. In step A, the state variable quantity x representing the dynamic internal state of the engine estimated in the previous control cycle is
1 to X3 (previously calculated value) and the calculated control input value δP
A, δIT, and δN, which is the control output value, are weighted and added to calculate each state variable amount X, to x4.

However, the matrix of equation (6) (A-GC month end, This is an example of forming a finitely settled observer in the form.

Note that (A, B, C) uses the observable canonical form (・te(・ru).

In step 39, the estimated dynamic internal state variables of the engine X, ~
7Ll', calculate how much force to increase the control input value.

The coefficients E) ij + gi + kij, etc. in Fig. 6 are calculated in advance and stored in a microcomputer, etc. (
.

Using the above procedure, we compared the results of experiments on the transient response to various disturbances when the idle rotation speed is constant and the transient response when the target value of the idle rotation speed is changed. Figures 7 to 10 show a comparison with the control.

FIG. 7 shows the transient response of the idle rotation speed N when the clutch is engaged (the clutch is half engaged at 10 points, but the brake is depressed), (A) is the conventional PI control, (Bl is the multivariable variable of this invention). In the case of control, Figure 8 shows the transient response when the clutch is disengaged (disengaged at 10 points).
(B) is the case of the method of this invention.

Figure 9 shows the target idle rotation speed Nr when the air conditioner is turned on.
80 rpm, and when the air conditioner is turned off and the target idle rotation speed Nr is returned to 650 rpm, (A) is the conventional method, (Bl is the method of the present invention. Figure 10 shows the transient response when coasting from a no-load high speed state to the target value Nr'' 650rpm, and (A) shows the conventional method, CB+
is the case with the method of this invention. As is clear from FIGS. 7 to 10, it can be seen that in all cases, the method of the present invention significantly improves the transient response. In addition, in FIG. 7(A), the idle rotation speed is not aligned with the target value Nr.

Figure 11 shows the experimental results when the gear is set to neutral during high-speed rotation. Each method is shown below. (Bl has a target rotational speed Nr "" 650r
It can be seen that the drop from pm is small.

In addition, in (B), the initial value explained in step 34 of FIG. 6 is set at the point t where the engine rotational speed passes 1.1.0 Orpm.

Figure 12 shows the experimental results when the clutch is disengaged after deceleration by engine braking, (Al is the conventional method, (Bl is the method of the present invention). [The clutch is disengaged at 1. (
It can be seen that B) has a smaller drop from the target rotational speed Nr.

As mentioned above, when controlling the internal combustion engine in this invention with the power being the idle speed, the control inputs include the air amount (or equivalent amount), ignition timing, fuel supply amount (or equivalent amount), and exhaust gas recirculation amount. (or an equivalent amount) can be used, and in the above embodiment, the control of the V C'M valve, which is an equivalent amount of the binox air amount, can be used. The case where the solenoid drive width (117 width) and ignition timing are used as control inputs has been described.

(Effects of the Invention) As explained above, according to the method for controlling the idle rotation speed of an internal combustion engine of the present invention, the idle rotation speed is controlled by applying a multivariable control method based on a dynamic model of the internal combustion engine. Moreover, it adds a step to estimate the dynamic state of the internal combustion engine, reduces calculation time by using a reduced-dimensional version of the engine model in the state observer, and absorbs the approximation error by integral operation. As a result, it is possible to optimize the control transient response to disturbances such as misfire disturbances and load disturbances, which are problems in the idling state.Moreover, in order to increase the degree of control freedom and improve controllability, multivariable control inputs are added to the control. It is also easy to do so, and the effect that more stable idle rotation speed control can be achieved can be obtained.

In particular, since the idle judgment is performed by focusing on the idle switch and the ratio between the vehicle speed and the engine rotation speed, the engine is less likely to stall when out of gear during high-speed rotation, and the stall resistance after decelerating with engine braking is improved. The effect is that it is possible to realize more stable idling operation.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a conventional idle rotation speed control device for an internal combustion engine, Fig. 2 is a flowchart showing a conventional idle rotation speed control method, and Fig. 3 is a realization of the idle rotation speed control method for an internal combustion engine according to the present invention. Fig. 4 is a detailed block diagram of the integral operation and gain block shown in Fig. 3, Fig. 5 is a block diagram showing the relationship between the control input/output and the engine shown in Fig. 3, and Fig. 6 is A flowchart explaining the control method according to the present invention, FIGS.
Figure 9 shows the experimental results of the transient response when the clutch is disengaged.
Figures (A) (B+ are diagrams showing the experimental results of the transient response when turning on and off the air conditioner, Figures 10 (A) and (B) are diagrams showing the experimental results of the transient response during coasting, Figure 11 (A) (
B) is a diagram showing the experimental results during high-speed gear removal with and without using the 211 Torals inch for idle determination, and Figure 12 (A) (Bl is the result when the clutch is disengaged after deceleration with engine braking. It is a diagram showing experimental results. 1... AAC valve, 2... VCM valve, 3
...Control solenoid, 4...Throttle valve, 5...Bypass, 7...Throttle valve switch, 8...211 Toralsinochi, 10...Water temperature sensor, 11...Air conditioner switch, 12... Internal combustion engine (controlled object), 13... Condition observation device, 14... Integral operation and gain block, N... Actual value of idle rotation speed, Nr... Target value of idle rotation speed , N,...Reference setting value of idle rotation speed, SA...Difference between target value and actual value of idle rotation speed, PA...Driving pulse width of control solenoid that defines bypass air amount, IT...・Ignition timing! (=xi)...Amount of state variable, X ("Xi)...Estimated amount of state variable. Patent applicant: Nissan Motor Co., Ltd. Patent application agent Megumi Yamamoto - Act 3 diagram pole, 4U!J 4 Act 7 diagram (A) g!f藺i (S扛) (8n time f, (Sere leather, 8r:!J (A) (8) Time opening t (6e り駦でＧ) (A) 'B%MIf; (sec) (δngin%'T 6 (sesu21E, 10 concave (A) CB)

Claims (1)

[Claims] When the internal combustion engine is idling, the target value N of the idle rotation speed
In a method for feedbank controlling an idle rotation speed based on a deviation SA between r and an actual value N, a throttle valve, which is a control input value of the internal combustion engine, is bypassed based on a dynamic model of the internal combustion engine stored in a controller. the amount of bypass air supplied to the internal combustion engine or the amount equivalent to the amount of bypass air; the ignition timing of the internal combustion engine; the amount of fuel supplied to the internal combustion engine or the amount equivalent to the amount of fuel supplied to the internal combustion engine; Any one selected from the exhaust gas recirculation amount or the amount equivalent to the exhaust gas recirculation amount.
or any combination of two or more and the idle rotational speed which is the control output value of the internal combustion engine, a state variable quantity xi (i=1. 2...., n), determine the control input value from the estimated state variable amount x1, and further determine whether to perform idle rotation speed control,
A method for controlling idle rotation speed of an internal combustion engine, characterized in that control is performed using a throttle valve switch, a ratio between vehicle speed and engine rotation speed, and engine rotation speed.