JPS6380044A - Non-linear feed-back control method for internal combustion engine - Google Patents

Abstract

PURPOSE:To make it possible to perform the feed-back control of an internal combustion engine over a wide range of operation, by computing a feed-back control input amount in accordance with a dynamic physical model which is described without deteriorating the non-linear dynamic characteristic of the engine. CONSTITUTION:An ECU 3 drives a motor 19 and an ISV 21 in accordance with a program previously stored in a ROM 3b with the result of detection by an intake-air sensor 31, a rotational speed sensor 32, a throttle position sensor 33 and an accelerator sensor 34 to perform the feed-back control of an engine so that the rotational speed of the engine is set to be a desired rotational speed. In this arrangement, a feed-back control input value is determined by the sum of a linear computation and a non-linear computation from input signals from an intake-air pressure sensor 31 and a rotational speed sensor 32 in accordance with a dynamic physical model having an amount corresponding to the intake-air pressure of the engine 2 and an amount corresponding to the rotational speed of the engine 2 as status variables. Thereby it is possible to perform feed-back control which is applicable to a wide range of non-linear operation.

Description

[Detailed Description of the Invention] Purpose of the Invention [Field of Industrial Application] The present invention relates to a method for controlling the rotational speed of an internal combustion engine, and particularly to a nonlinear feedback control method for an internal combustion engine that extends linear control theory (modern control theory). .

[Prior Art] Conventionally, control devices for internal combustion engines based on linear control theory have been proposed because of their high stability and high responsiveness. For example, Japanese Patent Laid-Open No. 59-120751. This control theory is
This is performed by linearly modeling the dynamic characteristics of the internal combustion engine, actuators, sensors, etc. in advance. However, the internal combustion engine in particular changes greatly depending on its operating conditions and environment, and has strong nonlinearity. Therefore, in the above-mentioned JP-A-59-120751, etc., which use a fixed dynamic model, for example, depending on the state of engine rotation speed and engine temperature, a model that assumes a certain rotation speed range or a state after warm-up may be used. is greatly affected, and the robustness becomes extremely low.
There was a problem that the rotation speed could not be controlled normally.

[Problems to be Solved by the Invention] In order to solve this problem, it has been considered to connect and use a plurality of linear models depending on each state of the internal combustion engine. However, its application has been difficult and rare because the control system has become complicated, resulting in control with low responsiveness, and it is impossible to predict what phenomena will occur when changing the model at the boundary between each model.

For this reason, it has been desired to apply modern control theory that takes into account the nonlinearity of internal combustion engines.

Therefore, the present invention employs the following configuration with the purpose of solving the above problems.

[Means for solving the problem, that is, the gist of the present invention is to stably control the actual rotational speed or to control it so that it matches the target rotational speed (p. 6), as illustrated in FIG. ), based on a dynamic physical model (M) whose state variables are an amount corresponding to the pressure of the intake air of the internal combustion engine and M corresponding to the rotational speed, at least the pressure of the intake air. A linear operation (p3) between the measured value (pl) of the quantity corresponding to , and the measured value (p2) of the quantity corresponding to the rotation speed.
), and the actual measured value of the amount corresponding to the pressure of the intake air (p
l) and an actual measured value (p2) of a quantity corresponding to the rotational speed (p4) of the valve, and determining a feedback control input value from Nero (p5) of the valve. be.

Here, the proviso corresponding to the pressure of the intake air corresponds to other m corresponding to the pressure of the intake air in addition to the pressure of the intake air itself. The m corresponding to the rotational speed includes not only the rotational speed itself but also other quantities corresponding to the rotational speed such as the angular velocity.

[Effect] Since the dynamic physical model uses state variables that correspond to the intake air pressure and rotation speed of the internal combustion engine, the values of the state variables can be directly measured, and the values can be calculated using a predetermined optimal feedback gain. It can be processed and returned as a feedback control input value.

is processed with a predetermined optimal feedback gain and returned as a feedback control input value, so it is possible to provide a feedback control input value that takes into account the nonlinearity of the internal combustion engine, and it is possible to provide a feedback control input value that takes into account the nonlinearity of the internal combustion engine. Feedback control that can be applied to a range becomes possible.

Next, examples of the present invention will be described. The present invention is not limited to these, but includes various embodiments without departing from the gist thereof.

[Embodiment] Next, a preferred embodiment of the present invention will be described in detail based on the drawings. An engine system to which an embodiment of the present invention is applied!
! ! Figure 2 shows the system configuration of the device.

The engine control device 1 includes a four-cylinder engine 2 and an electronic control device (hereinafter simply ECtJ) that controls the engine 2.
Toyo, ball. ) consists of 3. The engine 2 includes a first combustion chamber 4 formed from a cylinder 4a and a piston 4b, and second to fourth combustion chambers 5, 6.7 having a similar configuration.
It is a gasoline internal combustion engine equipped with.

Each combustion chamber 4.5, 6.7 has an intake valve 8,9°10.
11 to intake boats 12, 13, 14, and 15, respectively. Upstream of each intake port 12, 13, 14, 15, there is a surge tank 16 that absorbs the pulsation of intake air.
is provided, and the intake pipe 1 upstream of the surge tank 16
A throttle valve 18 is disposed inside 7. The throttle valve 18 is driven by a motor 19.

The motor 19 changes the opening degree of the throttle valve 18 in response to a command from the ECU 3, and adjusts the amount of intake air flowing through the intake pipe 17. Further, the intake pipe 17 is provided with a bypass passage 20 that bypasses the throttle valve 18,
An idle speed control valve (hereinafter simply referred to as 15CV) 21 is interposed in the bypass passage 20. 15CV21 opens and closes in response to commands from the ECU 3 to adjust the amount of intake air flowing through the bypass path 20.

The engine 2 also operates in conjunction with an igniter 22 equipped with an ignition coil that outputs the high voltage necessary for ignition, and a crankshaft 23 to distribute and supply the high voltage generated by the igniter 22 to spark plugs (not shown) of each cylinder. It has a distributor 24.

The engine control device 1 has a surge tank 16 as a detector.
An intake pressure sensor 3 is installed in the intake air pressure sensor 3 to detect the pressure of intake air.
1. 1/24 of the camshaft of the distributor 24
A rotation speed sensor 32 outputs a rotation angle signal every rotation, that is, every integral multiple of a crank angle of 0° to 30°, a throttle position sensor 33 detects the opening of the throttle valve 18, and the amount of depression of the accelerator pedal is detected. Replace the accelerator sensor 34.

The detection signals of each of the above sensors are input to the ECU3, and the
U3 controls engine 2. ECU3 is CPU3a
, ROM 3b, and RAM 3c as a logic operation circuit, and is connected to an input section 3e and an output section 3f via a common bus 3d to perform input/output with the outside.

The ECU 3 controls the motors 19 and 15CV2 based on detection results input from the intake pressure sensor 31, rotational speed sensor 32, throttle position sensor 33, or accelerator sensor 34 according to a program stored in advance in the ROM 3b.
1 and performs feedback control to set the rotational speed of the engine 2 to the target rotational speed.

Next, a control system used for this feedback control will be explained based on the block diagram of FIG. 3(A). Figure 3 (A> is a block diagram showing the system. It does not show the hardware configuration. Figure 3 (
The control system shown in A) is actually realized as a discrete system by executing a series of programs shown in the flowchart of FIG.

As shown in FIG. 3(A), the nonlinear calculation unit P1 includes coefficient calculation units P4. It may be a linear arithmetic unit that calculates the first feedback amount by multiplying the sum S' of the outputs of P6 by an element F related to the rotational speed N and intake air pressure P of the enciphered back gain F-.

The target rotational speed setting section P2 is for setting the target rotational speed Nr of the engine 2. For example, in idle rotation speed control, it is a predetermined idle rotation speed, and in normal driving conditions, it is a rotation speed commanded from the accelerator sensor 34 via the accelerator pedal, a rotation speed commanded from an automatic transmission control device, or The rotation speed commanded from the so-called auto drive control device is the target rotation speed N.
It becomes r.

The successive addition unit P3 accumulates the deviation e between the target rotational speed Nr and the actual rotational speed N to calculate a successive addition value Σe.

The coefficient multiplier P4 multiplies the successive addition value Σe by an element f related to the successive addition value Σe of the optimal feedback gain "', which will be described later, to exceed the limit (in this case, the upper and lower limits) set by the limiter P7. In this case, the second feedback amount is calculated by fixing it to the upper limit value or the lower limit value, respectively.

Limiter P7 has a function to prevent abnormal control when the absolute value of Σe becomes infinitely large due to failure to match the target value for some reason, and the disturbance that caused it is no longer present. have Also, as expected,
Overshoot and undershoot caused by Σe can be minimized.

Control 13'' is calculated by adding the first feedback amount and the second feedback amount.

On the other hand, the multiplier P5 calculates a multiplication value PN obtained by multiplying the actual rotational speed N of the engine 2 by the intake air pressure P.

Further, by subtracting the correction value from the control amount S-, the operation amount S for adjusting the intake air amount of the engine 2 is calculated. The manipulated variable S is the effective cross-sectional area of the intake throttle of the engine 2. That is, the amount corresponds to the sum of the opening degrees of the throttle valves 1B and 15CV21.

The hardware configuration of the engine control device 1 and the configuration of the control system realized by executing the program described later have been described above. Next, construction of a dynamic physical model of the engine 2 and calculation of the @optimal feedback gain F' will be explained.

First, a dynamic physical model of engine 2 is constructed. The equation of motion of the engine 2 in the operating state can be written as the following equation (1).

(dVci/dθ)-Tf-TIQco...(1) However, N is the rotational speed, t is time, ■ is the moment of inertia of the rotating part of the engine, n is the number of cylinders, Pci is the pressure in the first cylinder, lea is atmospheric pressure, θ is crank angle, ■ci is 1
th cylinder volume, Tf is machine a @ lost torque, and TQ is actual load torque.

On the other hand, the law of conservation of mass of intake air in a cylinder in the intake stroke of the engine 2 can be described as shown in the following equation (2).

d P/d t = (C2/V) ・[S-m-Σ(Kc/(KC-1
>-P-(dVCi/dt>-qm)/((Ki/
(Ki −1))・Ri −Ti) 1 piece...
(2) However, P is the intake air pressure, C is the speed of sound, S is the effective cross-sectional area of the intake throttle, m is the amount of intake air per unit area, KC
is the air-fuel mixture specific heat ratio, qm is the cylinder wall heat transfer amount, K1 is the intake air specific heat ratio, Ri is the intake air gas constant, T1 is the intake air temperature, and ■ is the intake air volume. Note that the terms marked with "*" are zero except for the intake stroke.

It can be approximated as

(1/1)-[,Σ(1)ci-Pa) (d Vc
i/dθ)]sl N =α1・P (3) In the above equation (2), if the cylinder pressure PC1 is below the critical pressure, the intake air amount is proportional to the effective cross-sectional area S of the intake throttle. can be approximated as shown in the following equation (4).

(C2/V)-3 m=α1-s +++ (4
) Also, in the above equation (2), the amount of intake air taken into the cylinder is determined by the rotational speed N of the engine 2 and the intake air pressure P.
Since it is proportional to the product of , it can be approximated as shown in the following equation (5).

-(02/V)[χ((KC/ (KC-1))・P・
+++ (dVci/dt) -CHD)/((Ki,/
(Ki −1))・R1・Ti)] book=α2・P−N
(5) Note that the terms marked with "ne" are zero except in the intake stroke.

The above equations (1), (
2) can be approximated as shown in the following equation (6), (l).

dN/dt=α1・P×α2・Tf×α3・TQ・・
・(6) d P/d t = α1・S+α2・P−N ・・
・(7) Discretize the above equations (6) and (7) using Euler's equation or integration, and roughly calculate the machine I21 loss torque T
If fG is approximated as being proportional to rotational speed N and each constant term is revised, the following equations (8) and (9), which are basic identification equations in the case of constant time sampling, are obtained.

N(K+1)=α1 ・N (K) ten α;・P (K)
P(K+1)=α1・P(K)+α;・5(K)+α3
・P (K>・N (K)...(9) Here, the actual load torque α1・Trl(K) and the constant term α4 are expressed by the following equation (10
) to convert the load torque to T-(K>).

α3T-(K)=α3・(T12(K)+(α'4/α1))...(1
o) Also, the effective cross-sectional area of the intake throttle, S (K>
is converted into a control @ff1s'' (K) as shown in the following equation (11).

S= (K) =S (K> + (α3/α2)・P (K)・N
(K)...(11) Note that each constant term in both equations (8) and (9) above is identified by the least squares method.

Using the above equations (10) and (11), the above equations (8) and (9
) is linearized, the following equation (12) is obtained.

In this way, the dynamic physical model of this example is expressed by the above equation (1
2) is calculated as follows. This dynamic physical model is a linearized version of the nonlinear engine 2.

Next, we will explain how to find the optimal feedback gain F', but the method to find the optimal feedback gain F' is, for example, "Digital Control of Actual Systems" by Katsuhisa Furuta, System and Control, ■O1, 28, No. 12 ( 19
1984) Since I am familiar with the Society of Instrument and Control Engineers, etc., I will omit the detailed explanation here and only show the results.

First, the target rotational speed Nr and the load torque T as a disturbance
Assuming that ′ changes stepwise, the rotational speed N (
By introducing the deviation e (K) from the equation (12) above, the system represented by the equation of state of equation (12) is expanded to a servo system. The Smith-Devison design method is used here. Deviation e (K
) can be written as in the following equation (13).

e (K) = N (K> = Nr ・(
13) Assuming that the target rotational speed Nr changes stepwise, and finding the difference Δe (K) of the deviation e (K), a relationship as shown in the following equation (14) is derived.

Δe (K> =e (K) −e (K−
1>=N (K) −N (K−1> −(Nr (K>−Nr (K−1>)=ΔN (
K) ...(14) Therefore, the deviation e
(K> can be written as in the following equation (15).

e (K) = ΔN (K> +e (K-1> ・
(15) From the above equations (12) and (15), when the system expanded to the servo system is expressed in terms of the difference value, an equation of state as shown in the following equation (16) is obtained.

・ΔS= (K) ...(1
6) Regard the above equation (16) as the following equation (17).

δX(K+1>=l)a−δX (K)+Ga −δu (K>−(1
7) Then, the discrete quadratic evaluation function can be expressed as the following equation (18).

J=Σ [δX (K) ・Q・δX (K) −
0 + δu” (K>-IR-δu (K) ]-(18
>Here, the weight parameter matrix 0. The input δU(K) for selecting IR and minimizing the discrete quadratic evaluation function J is given by the following equation (19).

δu(K)=IF−−δX(K)−(19)
Therefore, the optimum feedback gain "-" is determined as shown in the following equation (20).

F-'=-(IR+Ga''-M-Ga)-1-G
a ” -M-Pa -(20) However,
M is a constant symmetric matrix that satisfies the discrete Rikkatchi equation shown in the following equation (2-).

M=Pa''-M-Pa +G-(Pa''-M-Ga) ・ (lR+Ga ''-MG)-1- (Ga ding・M-Pa) ・(21>This leads to the deviation of the control amount S'(K) is found as shown in the following equation (22).

ΔS′(K)= However, F-=[F f].

By integrating the above equation (22), the control amount S'(K) is determined as shown in the following equation (23).

...(23) The construction of the dynamic physical model of the engine 2 and the calculation of the optimal feedback gain F' have been explained above.
Optimum feedback gain ``- is calculated in advance, and E
Inside the CU3, actual control is performed using only the results.

Next, the engine control process executed by the ECU 3 will be explained based on the flowchart shown in FIG. 4. In addition, in the following explanation, the amount pumped in the current process is indicated by the subscript (K).
It is expressed as This engine control process is started when the ECU 3 is started.

First, in step 100, initialization processing is performed to set the register register inside the CPU 3a and the second feedback amount ie to O as initial values.

In the following step 110, a process of inputting the target rotational speed Nr is performed. For example, the output value of the accelerator sensor 34 is read and set as the target rotation speed. This Nr may be received from other controls, such as idle rotation speed control and auto drive control. Next, the process proceeds to step 120, where a process is performed in which the rotational speed N (K>) is inputted from the rotational speed sensor 32, and the intake air pressure P (K) is inputted from the intake pressure sensor 31, respectively.

Next, the process proceeds to step 130, where the rotational speed N (K) detected in step 120 and the intake air pressure P (K
) is multiplied by the optimum feedback gain "-element" to obtain the first feedback amount, and the second feedback @ie is added to the first feedback amount to determine the control amount S-(K) as shown in the following equation ( 24) is performed.

S"' (K) = F1 1 ・ N (K)
+F1 2 ・P (K)+ie
...(24) The process of this step 130 is
It functions as the linear calculation unit P in FIG. 3 (A>).

In the subsequent step 140, the intake throttle effective cross-sectional area S (K), which is the operation group (feedback control input value), is calculated from the control ff1s'' (K) calculated in the step 130 as shown in the following equation (25). will be carried out.

S (K)=S= (K>-(α3/α2)・P (K
)・N (K> ...(25) This step 1
40 functions as the multiplication section P5 and the coefficient multiplication section P6 in FIG. 3 (A>).

Next, the process proceeds to step 150, and the deviation e (K>) between the target rotation speed Nr input in step 110 and the rotation speed N (K) input in step 120 is calculated using the following equation (26).
The calculation process is performed as follows.

e (K)=N (K) −Nr −
(26>In the following step 160, the above step 150
The product of the deviation e (K) calculated in
A process is performed to calculate the feedback lie as shown in the following equation (27).

i e=ie ten f−e (K) −(2
7) Note that it is also suitable to provide upper and lower limit values for the second feedback lie and to limit the maximum and minimum values in order to ensure stability of control against unexpected disturbances.

The processing in step 160 functions as the successive addition section P3 and coefficient multiplication section P4 in FIG. 3(A).

Next, the process proceeds to step 170, in which the drive signal corresponding to the operation ff1s (K> calculated in step 140 above is output to the motor 19 or l5CV21 via the output section 3f. Alternatively, S (K) can be converted to another controlled variable. You can also pass it as

For example, operation=s(K> means l5CV2 when idle
It can be used as the operation amount of 1, the operation amount of the motor 19 of the throttle valve 18 during auto drive, and the operation amount of an appropriate operation target depending on the type of control.

In the following step 180, the value 1 is added to the subscript K indicating the number of times of sampling, calculation, and control, and after processing to update the subscript K, the process returns to step 110. Thereafter, this engine formation processing will be performed in steps 110 to 18 above.
Execute 0 repeatedly.

Fig. 5 shows the results of actually measuring the responsiveness of the actual rotational speed N by changing the target rotational speed N in various steps in the configuration of the above embodiment.
It can be seen that even with various changes over a wide range of 4000 rpm, the responsiveness is extremely good and stable feedback control is performed. If the actual rotational speed, intake pressure, and deviation between the actual rotational speed and the target rotational speed are simply processed and returned as feedback control input values, stable control is not possible unless the rotational speed fluctuates in an extremely limited range. Yes, it cannot actually be adopted.

Also, of course, even when compared to the PID control shown in FIG. 6, it exhibits extremely superior responsiveness and stability. The stability in idle rotational speed control shown in FIG. 7 and the stability of rotational speed against rectangular load torque disturbances shown in FIG. 8 are also extremely excellent.

In the above embodiment, in order to make the feedback control input value match the target rotation speed, a value determined from the integral amount of the deviation between the actual measured rotation speed of the internal combustion engine and the target rotation speed is added. Instead of providing the sequential addition unit P3 for calculating the amount, the deviation may be multiplied by a coefficient and then added to the feedback υ1611 human power value with or without the limiter P7.

Further, as shown in FIG. 3(B), the feedback control input value S' may also be input to calculate the feedback control input value instead of the linear calculation section P1. The design of the dynamic system can be realized using various well-known techniques such as those described in the above-mentioned literature and others.

Although the embodiments of the present invention have been described above, the present invention is not limited to these embodiments in any way, and it goes without saying that it can be implemented in various forms without departing from the gist of the present invention. .

Effects of the Invention As detailed above, according to the nonlinear feedback control method for an internal combustion engine of the present invention, intake air is Linear calculation between the measured value of a quantity corresponding to pressure and the measured value of a quantity corresponding to rotational speed, and non-linear calculation between the measured value of a quantity corresponding to intake air pressure and the measured value of 5 corresponding to rotational speed. Since the feedback control manual power output is calculated from the sum of the above, the feedback control of the internal combustion engine can be performed over a wide range of operating conditions, and its responsiveness, followability, and robustness are improved.

[Brief explanation of the drawing]

Fig. 1 is a basic configuration diagram conceptually illustrating the content of the present invention, Fig. 2 is a system configuration diagram of an internal combustion engine to which this embodiment is applied, and Fig. 3 (A> is a block diagram of the control of this embodiment). Diagram, Figure 3 (B) is a block diagram of an example control using a dynamic system that linearly calculates the feedback control input value based on the feedback control input value, actual rotational speed, and intake air pressure, and Figure 4 is the electronic control diagram. A flowchart of the processing performed by the device, FIG. 5 is a graph showing responsiveness and stability of this embodiment, FIG. 6 is a graph based on PID control, FIG. 7 is a graph showing stability in idle rotation speed control, FIG. 8 is a graph showing the stability of rotational speed against torque disturbances. ]...Internal combustion engine control device 2...Internal combustion engine 3...Electronic control device 18...Throttle valve 19... Motor 21... Idle speed control valve (IS
CV) 31... Intake pressure sensor 32... Rotational speed sensor 33... Throttle position sensor 34... Accelerator sensor

Claims (1)

[Claims] 1. In a feedback control method for an internal combustion engine that stably controls the actual rotational speed or controls the actual rotational speed to match a target rotational speed, Based on a dynamic physical model in which the corresponding quantities are state variables, at least linear calculation of the measured value of the quantity corresponding to the pressure of the intake air and the measured value of the quantity corresponding to the rotational speed, and A nonlinear feedback control method for an internal combustion engine, characterized in that a feedback control input value is determined from the sum of a nonlinear calculation of an actual measurement value of a quantity equivalent to pressure and an actual measurement value of an quantity equivalent to rotational speed. 2. A value determined from the integral amount of the deviation between the actual measurement value corresponding to the rotational speed of the internal combustion engine and the target rotational speed is added so that the feedback control input value matches the target rotational speed, and from the above integral amount 2. A nonlinear feedback control method for an internal combustion engine according to claim 1, wherein the determined value is limited. 3. The linear calculation is performed by a dynamic system that receives as input a feedback control input value, an actual measurement value of an amount corresponding to the pressure of intake air, and an actual measurement value of an amount equivalent to the rotational speed. The nonlinear feedback control method for an internal combustion engine according to item 1.