JPH01113574A - Control device for internal combustion engine - Google Patents

Abstract

PURPOSE:To quickly converge to a target value by correcting a membership function stored in storage means according to an engine operating condition and setting the controlled variable of an object of control by fuzzy reasoning using the corrected membership function. CONSTITUTION:In a control device where according 10 an operating condition detected by operating condition detecting means A, a designated object (ignition timing, air-fuel ratio or the like) of control of an engine is feedback-controlled, there is provided membership function storage means B for storing a membership function is fuzzy reasoning. Further, there is provided membership function correcting means C for correcting a membership function stored in the storage means B according to the detected operating condition. Then, fuzzy reasoning is performed using the membership function corrected by the correcting means C by controlled variable setting means D to set the controlled variable of an object of control. Thus, during transient operation, convergence to a target value can be expedited rapidly.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a control device for an internal combustion engine that performs feedback control, and particularly to one that uses fuzzy inference to improve control accuracy.

<Prior Art> Conventional feedback control for internal combustion engines includes, for example, ignition timing control. - An example will be explained with reference to FIG. 7. First, the basic ignition timing θ is determined based on the detected value of the engine operating state (rotational speed load) (step 1).

Next, the crank angle θPyaax that gives the maximum value of the cylinder pressure measured by the cylinder pressure sensor is detected (step 2).

Next, the θF+*sx is compared with the crank angle θ□7 (for example, 15°) that gives the optimum ignition timing MBT (Step 3), and if θPmax is smaller than θ□7, the ignition timing θ1 is delayed by a unit angle α (Step 4). , θ, □ are θN11? If it is larger, the ignition timing θ is increased by unit angle,
(Step 5).
-35065).

<Problems to be solved by the invention> However, in such conventional feedback control systems, the same control is performed even in the transient state of engine operation as in the steady state, so depending on the movement of the vehicle, the engine may The control cannot follow transient changes in operation well, the ignition timing control does not generate optimal torque, and the knocking control has problems such as not being able to quickly avoid knocking. Attempting to perform extremely fine tuning to avoid this would require an extremely large number of man-hours.

The present invention was developed in view of these conventional problems, and uses fuzzy inference to constantly obtain optimal control characteristics, and also changes the shape of the membership function used in the fuzzy inference to the engine operating state. It is an object of the present invention to provide a control device for an internal combustion engine that solves the above-mentioned problems by making changes accordingly.

Means for Solving the Problems> For this reason, the present invention provides an internal combustion engine control device that performs feedback control of a predetermined control target of the engine according to the operating state detected by an operating state detection means. membership function storage means for storing a function; membership function modification means for modifying the membership function stored in the membership function storage means according to a detected driving state; and control amount setting means for setting the control amount of the controlled object by performing fuzzy inference using the membership function modified by the membership function modification means.

<Operation> The membership function stored in the membership function storage means is modified by the membership function modification means in accordance with the driving state detected by the driving state detection means, and the modified membership function is used to perform fuzzy inference. The control amount setting means sets the control amount of the control target such as the ignition timing and the air-fuel ratio.

As a result, even if the amount of deviation of the detected value from the control target value of the controlled object becomes large during transient operation, for example, the feedback correction amount of the control 4ift can be increased according to the amount of deviation. It is possible to perform control, quickly converge to a target value, and improve transient drivability. Furthermore, even if the operating state changes temporarily during steady operation, it is possible to quickly return to the original state.

<Example> Embodiments of the present invention will be described below based on the drawings.

FIG. 2 shows a system configuration of an embodiment of the present invention.

In the figure, an in-cylinder pressure sensor 2 for detecting the pressure in the combustion chamber la (in-cylinder pressure) is installed as a washer for a spark plug 3, and the in-cylinder pressure signal from the in-cylinder pressure sensor 2 is transmitted to an amplifier 4. By fuzzy inference after being amplified by
The signal is input to the controller 5 which sets the ignition timing.

The ignition advance value signal set by the controller 5 is input to the ignition control circuit 6, and the control circuit 6 controls the ignition coil 8 based on the ignition advance value signal and the crank angle signal input from the crank angle sensor 7. By controlling the energization to the transistor 9 connected to the primary side and cutting off the energization at the set ignition timing, a high voltage is generated on the secondary side of the ignition coil 8 to spark the ignition plug 3 and ignite it. I do.

Note that the signal from the crank angle sensor 7 is also input to the controller 5.

Furthermore, the cylinder pressure sensor 2 and the crank angle sensor 7 correspond to operating state detection means.

Next, a method of setting the ignition advance value using fuzzy inference by the controller 5 will be explained with reference to the flowchart shown in FIG.

First, in step 11, a crank angle θPM□8 that maximizes P is calculated based on the cylinder pressure Pc input from the cylinder pressure sensor 2 via the amplifier 4 and the crank angle signal θ input from the crank angle sensor 7. .

Next, in step 12, the above-mentioned θPmax and the optimum ignition timing θ
, 1゛, the deviation Δθ is calculated.

In step 13, fuzzy inference is performed on the deviation Δθ to determine the ignition advance value θ. Set 9.

The fuzzy inference is performed as follows.

Figure 4 lists the linguistic control rules for this control, and the antecedent and fuzzy quantities are set as shown in Figure 5 for the antecedent and consequent propositions of each term. The membership function and the consequent membership function are stored in the ROM of the microcomputer that constitutes the controller 5. That is, the ROM constitutes membership function storage means.

Here, there is a one-term control law that states, "When Δθ is positive, the ignition timing is advanced by °°," and a two-term control law that is, "When Δθ is negative, the ignition timing is retarded." For each antecedent membership function, fuzzy properties are added to perform ultra-fuzzy inference.

That is, the antecedent membership functions of the first term and the second term are set as, for example, ψtan-'Δθ+C2-ψtan-'Δθ10, and the shape changes depending on the value of the parameter ψ.

The value of the parameter ψ is determined by the antecedent membership function and the consequent membership function for the control law in terms 5 and 6.

In other words, for the control law in section 5, which states that ``When the absolute value 1ΔθI of the deviation Δθ is large, the parameter ψ is increased,'' the area characteristics as shown in the figure are determined as shown in Figure 6, and the Similarly, the area characteristics of B shown in the figure are determined for the control law of 6 terms, ``when the parameter ψ is made small. = ψI) (S13A).

By substituting ψ1 obtained in this way to the parameter ψ of the membership functions of the first and second terms, the shapes of these functions are uniquely determined (313B). This part corresponds to the membership function modification means. Item 1 determined as above.

Using the two-term antecedent membership function and consequent membership function, μ
Find the correction amount (change) ΔθAVD of the angle value (S13C
).

Here, according to the fuzzy inference using the control law terms 5 and 6, the parameter ψ increases as lΔθ1 becomes larger,
Accordingly, the gains of the antecedent membership functions of the first and second terms become larger. Therefore, as 1Δθ1 increases, the advance angle value correction amount ΔθADV is set to become larger.
can be reduced in a short time to quickly converge to a new optimal ignition timing, obtain optimal torque, improve transient driving performance, and quickly avoid knocking.

In addition, with respect to the engine speed N obtained based on the signal from the crank angle sensor 7, the control side of the three terms ``When the engine speed N is large, the basic advance value θ□SE is increased.'' , “When the engine speed is low, the basic advance value θ□8
．． The sixth control law for the four-term control law ``to make small
The basic advance angle values θ□, E are obtained in exactly the same manner as shown in the figure (S13D).

Then, the ignition advance value ΔθADV is determined by adding the basic advance angle value θ8ASE obtained as described above and the correction amount ΔθADV (S13E).

These portions 513C to 313E correspond to control amount setting means.

The signal of the ignition advance value θADV determined in this manner is output to the ignition control circuit 6 as described above, and ignition is performed at the ignition timing corresponding to θADV.

Although the above embodiments have been applied to ignition timing control, they can also be applied to control the air-fuel ratio, etc., and in this case as well, the effect of properly setting the air-fuel ratio during transient operation is obtained. can get.

<Effects of the Invention> As explained above, according to the present invention, when performing feedback control in an internal combustion engine, the membership function used in fuzzy inference for control amount setting is modified according to the operating state. Even if the amount of deviation from the target value increases during a transient period, control can be performed to increase the amount of feedback correction as the amount of deviation increases, allowing the target value to be quickly approached, and the control target to be controlled even during steady state. Stability is maintained by avoiding situations where the state of the system changes significantly.

Therefore, by applying it to the control of ignition timing and air-fuel ratio,
Engine operating conditions can be significantly improved.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of the present invention, FIG. 2 is a diagram showing the system configuration of an embodiment of the present invention, FIG. 3 is a flowchart showing the ignition advance value setting routine according to the above embodiment, and FIG. The figure shows the control law of fuzzy inference used for setting the ignition advance value as above, Figure 5 shows the membership function corresponding to the control law as above, and Figure 6 shows the modification of the membership function as above. FIG. 7 is a flowchart showing an example of conventional ignition timing control. 1... Engine 2... Cylinder pressure sensor 5... Controller 7... Crank angle sensor Patent applicant Nissan Motor Co., Ltd. Representative Patent attorney Fujio Sasashima Tiger doctor
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Claims (1)

[Scope of Claims] In an internal combustion engine control device that performs feedback control of a predetermined control target of the engine according to an operating state detected by an operating state detecting means, a membership function storage means for storing a membership function in fuzzy inference. a membership function modifying means for modifying the membership function stored in the membership function storage means according to the detected driving state; 1. A control device for an internal combustion engine, comprising: control amount setting means for setting a control amount of the control target by performing fuzzy inference using a membership function.