JPS6330491B2 - - Google Patents

Description

Detailed Description of the Invention (Technical Field) The present invention considers the internal state of an internal combustion engine, treats the engine as a dynamic system, and uses state variables that define the internal state to improve the dynamics of the engine. This paper relates to a method of controlling idle rotation speed using a state variable control method that determines input variables of an engine while estimating its behavior, and in particular, preventing a decrease or increase in idle rotation speed in response to disturbances that can be predicted in advance. Regarding control method.

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

The control unit 6 detects that the engine is in the idle state based on the idle (IDLE) 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. Then, a basic target value of the idle rotation speed is calculated by a one-dimensional table lookup according to the cooling water temperature (T _W ) detected by the water temperature sensor 10. Then, correction is made according to the air conditioner (A/C) signal, neutral (NEUT) signal, battery voltage (VB) signal, etc. from the air conditioner switch 11, and the target value N _r of the idle rotation speed is finally calculated. On the other hand, the deviation SA between the engine's actual idle speed N and its target value N _r
The pulse width of control solenoid 3 is set so that
Perform proportional and integral (PI) duty control on P _A ,
Perform feedback control to target rotational speed _Nr .

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

However, in such conventional methods for controlling the idle rotation speed of an internal combustion engine, the target rotation speed cannot be adjusted when a disturbance occurs from the idle state (for example, an air conditioner compressor load, a power steering pump load, a load due to clutch engagement). When controlling to increase the target rotation speed, or when controlling to decrease the target rotation speed when these disturbances (loads) are no longer present, feedback is poor due to poor control transient response until it follows the target rotation speed. Control alone has the problem that the rotational speed drops or increases relative to the target rotational speed.

(Purpose of the Invention) This invention was made by focusing on such conventional problems, and improves the transient response of the idle rotation speed when a disturbance occurs or ceases to occur, and improves the idle rotation speed. The purpose is to prevent the decline or rise of

(Structure and operation of the invention) Therefore, the present invention stores models of the dynamic characteristics of the internal combustion engine, actuator, and sensors in a controller including a microcomputer,
Either one of fuel supply amount (or equivalent amount) and exhaust gas recirculation (EGR) amount (or equivalent amount)
or any combination of two or more as the control input, and the idle rotation speed as the control output, and from the control input and control output, estimate the state variable amount representing the internal state of an internal combustion engine, etc., which is a dynamic model. , the estimated value and the integrated value of the deviation between the target value and the actual value of the idle rotation speed are used to determine the control input value, and the idle rotation speed of the internal combustion engine is feedback-controlled to the target value. This system is characterized in that feedforward control is applied to load disturbances that can be predicted in advance to occur.

The present invention will be explained below based on 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 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 is the amount of air (or equivalent amount), ignition timing, fuel supply amount (or equivalent amount), and exhaust gas recirculation amount (or equivalent amount). Any one or a combination of two or more may be used. In this embodiment, the VCM for adjusting the amount of bypass air at idle is used as the two control inputs.
The pulse width P _A (that is, the amount corresponding to the amount of bypass air) that drives the control solenoid of valve 2 (Fig. 1) and the ignition timing IT are determined. The control output is the idle rotation speed N, which is one output.

Reference numeral 13 denotes a state observer that stores a dynamic model of the engine 12 that is the object of control, and estimates the dynamic internal state of the engine from the above three control input/output information _PA , IT, and N. , the state variable quantity x representing the internal state (for example, 4
Calculate the estimated value x^ of the vector representation of the three quantities x ₁ , x ₂ , x ₃ , x ₄ ).

The state observation device 13 simulates the engine to be controlled, and the dynamic internal state is represented by a state variable x (nth order vector x ₁ to xn). Specifically, state variables representing the internal state of the engine 12 to be controlled 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 the fuel, the engine torque, etc. Can be mentioned. 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 by using the detected values for 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, but rather simulates the engine as a whole. As for the degree n of the state variable x, the larger n is, the more accurate the simulation will be, but on the other hand, the calculation will be more 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 the case of two inputs and one output in this invention, n=4 is appropriate.

In FIG. 3, 14 is an integral operation and a gain block, which is the integral of the deviation SA between the designated target value N _r of the engine rotation speed and the actual value N, and the state variable quantity x calculated by the state observer 13. From this, calculate the values of the two control inputs P _A and IT (see Figure 5).
The state observer 13, integral operation, and gain block 14 constitute a controller.

Next, the action will be explained.

The engine 12 that is the controlled object is a two-input one-output system, and the controlled object 12 is It is possible to estimate the dynamic internal state of
One of the methods is the state observation device 13. Under operating conditions near the idle rotation speed, the controlled object 12
The transfer function matrix T(z) of is found experimentally, and becomes T(z)=[T ₁ (z) T ₂ (z)] (1). However, z is the sample value of the input/output signal.
- transformation, where T ₁ (z) and T ₂ (z) are, for example, quadratic transfer functions of z.

FIG. 4 shows a model structure of the controlled object (engine) 12 showing the relationship between input, output, and transfer functions T ₁ (z) and T ₂ (z). However, input and output use deviations ΔP _A , ΔIT, and ΔN from the reference setting values, respectively.

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

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

u(n-1) is the control input vector, and the pulse width δP of the control solenoid 3 represents _the perturbation within the range where linear approximation from a certain reference setting value holds.
(n-1) and ignition timing δIT as elements. That is, Also, y(n-1) is a control output, which, like the control input vector, is a certain reference rotational speed Na (for example,
The element is δN (n-1) representing the perturbation from 650 rpm).

That is, y(n-1)=δN(n-1) (5) x(・) is the state variable vector, and the matrices A, B,
C is a constant matrix determined from the coefficients of the transfer function matrix T(z).

Here, we construct 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 estimated value of the internal state variable x(·) of the engine 12. Transforming from equations (2)(3)(6), [x(n)−x^(n)]=(A−GC)[x(n−1)−
x^
(n-1)] (7), and if G is chosen so that the eigenvalues of the matrix (A-GC) are within the unit circle, then x^(n)→x(n) (8) for n→large. , the internal state variable quantity x(n) can be estimated from the input u(·) and the output y(·). Also,
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.

The state variable x^(・) estimated in this way is
Target rotation speed N _r and current actual rotation speed N (・)
Using the information of the deviation SA = (N _r − N (・)),
The increase amount δP _A (・) within the range where a linear approximation from the reference set value (P _A )a of the drive pulse width of the control solenoid 3, which is the control input, holds, and the linear approximation from the reference set value of the ignition timing are The increase amount δIT(·) is determined within a valid range, and optimal regulator control of the idle rotational speed N of the engine 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 the present invention, since the experimentally obtained model is a low-dimensional approximate model as described above, an I (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-input one-output system, which is optimally controlled by a regulator. It is explained in the book "Linear System Control Theory" (1971) by Shokodo and others, so a detailed explanation will be omitted here. Describing only the results, now δu(n)=u(n)−u(n−1) (9) δe(n)=N _r −N(n) (10) and the evaluation function J is J = _∞ 〓 ^k=0 [δe(k) ² +δu ^t (k)Rδu(k)] (11). Here, R is a weight parameter matrix and t is a transposition. k is the number of samples with the control start time being 0, and the second term on the right side of equation (11) represents the square of equation (9) (assuming R is a diagonal matrix). Also, the second term of equation (11) is
The quadratic form of the control input difference as shown in equation (9) is used, but this is because an I (integral) operation is added as shown in FIG. The optimal control input u ^* (k) that minimizes the evaluation function J in equation (11) is becomes. If we set K=-(R+ ^tP ) ^-1tP (13) in equation (12), K is the ^optimal gain matrix. Also, in equation (12) and P is is the solution of the Riccati equation.

The meaning of the evaluation function J in equation (11) is that the control input u(・)
The intention is to minimize the deviation SA (rotation fluctuation) of the idle rotation speed N, which is the control output y (・), from the target value N _r while constraining the movement of It can be changed using matrix R. Therefore, by selecting an appropriate R, using a dynamic model (state variable model) of the engine at idle, and using P obtained by solving equation (16), the optimal gain matrix K in equation (13) is micro- The target value of idle rotation speed is stored in the computer.
From the integral value of the deviation SA between _Nr and the actual value N and the estimated state variable x^(k), the optimal control input value u ^* (k) can be easily determined by equation (12).
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,
The values of C and G may be stored in a microcomputer and calculated using equation (6).

The method explained above is feedback control, but if there is a load that can be predicted in advance from a signal from a switch, such as an air conditioner compressor load, a power steering pump load, or a load due to clutch engagement, the feedback control described above can be used. By performing feed forward control in addition to control, controllability during transient times can be improved.

An example of turning on and off the air conditioner is shown in Figure 7A.
This will be explained with reference to B. Figure 7A shows the case of normal feedback control, but the idle speed drops significantly as soon as the air conditioner is turned on.
When the air conditioner is turned off, the idle speed increases temporarily. FIG. 7B shows a case where control is performed by a method in which feedback control according to the present invention is added to the feedback control at the same time as the air conditioner is turned on and off.

A specific method for controlling the feed forward when turning on and off the air conditioner is to increase the on-duty pulse width of the duty signal that controls the control solenoid 3 of the VCM valve 2 by a predetermined amount ( For example, 4ms) and increase the amount of bypass air. This increment is removed when the air conditioner is turned off.

FIG. 6 shows the procedure of the above idle rotation speed control. When explaining the procedure, the step
At step 30, it is first determined whether or not to enter idle rotation speed control. If it is determined that the control is to be carried out, in step 31 the coasting engine will not stall.
_k 〓 ^j=0 [N _r −N (j)] = DUN, set the initial values of x ₁ to x ₄ . In step 32, a target value N _r of the idle rotation speed is determined based on the on/off state of the air conditioner, the water temperature T _W , etc. In step 33, the deviation SA between the target value N _r and the actual value N of the idle rotational speed is calculated. In step 34, 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 35,
The reference setting value Na of the actual value N of the rotation speed (e.g.
Calculate the deviation δN from 650rpm). step 36
is the state variable quantity x ^* ₁ ~ x ^* ₃ (previously calculated value) estimated in the previous control according to the algorithm that estimates the dynamic internal state of the engine, the calculated control input values δP _A and δIT, and δN, which is the control output value
Each state variable amount x ₁ to x ₄ is calculated by weighted addition. However, the matrix (A-GC) of equation (6) is This is an example of forming a finitely settled observer in the form. Note that (A, B, C) use observable canonical forms.

In step 37, the estimated dynamic internal state variables x ₁ to x ₄ of the engine and DUN= _k 〓 ^j=0 [N _r −N
(j)] is multiplied by the element kij of the optimal gain K and added,
Calculate how much the control input value should be increased with respect to the reference setting value (P _A )a and ITa.

In step 38, it is determined whether the air conditioner switch has been turned on or not. If it has been turned on, a constant value is entered in ΔP _A ' in step 39, and if it has not been turned on,
In step 40, δP _A ′ is set to 0, and when finally controlling the duty signal of VCM valve 2, δP _A ′ is added to δP _A ′ and outputted.
No feedback to 3.

The coefficients bij, gi, kij, etc. in Fig. 6 are determined in advance and stored in the microcomputer's ROM (Read Only).
Memory) etc.

The feedforward control method explained above is
Although a fixed value is added to the control input ΔP _A when the air conditioner is turned on, the amount of addition may be determined according to the elapsed time from the time when the air conditioner is turned on. When idle rotation speed control is performed in synchronization with engine rotation, the addition amount is determined according to engine rotation. In other words, the amount δP A ′ to be added to the control input δP _A is the function δP _{A ′} of the engine cumulative rotation speed N _ON from the time the air conditioner is turned on.
Let f(N _ON ).

The above description is about when the air conditioner is on, but when the air conditioner is off, subtraction is performed in the same way.

The above explanation has been about turning on and off the air conditioner, but similar control can also be performed using signals from the power steering pump or clutch switch.

8A and 8B show experimental results when a power steering pump load is applied. FIG. 8A shows a case using conventional feedback control, and FIG. 8B shows a case using feedback control according to the present invention. Power steering (turning the steering wheel while the vehicle is stopped) places the greatest load on the engine.

650 rpm is the steady idle rotation speed. 8th
It is clear that the control method according to the invention shown in FIG. B has better responsiveness.

9A and 9B show experimental results of the response of the idle rotational speed during clutch engagement and clutch off, with FIG. 9A showing the conventional method and FIG. 9B showing the method according to the present invention. It can be seen that the case according to the present invention shown in FIG. 9B has better responsiveness.

(Effects of the Invention) As explained above, according to the present invention, the control input (any one or a combination of any two or more of the air amount, ignition timing, fuel supply amount, and exhaust gas recirculation amount) Multivariable control is performed based on a dynamic model between control outputs (idle rotation speed),
Since the configuration is configured to perform feedforward control in addition to feedback control when a load disturbance that can be predicted in advance occurs, the transient response of the idle rotation speed when a load disturbance occurs and when the introduced load disturbance is removed. The effect is that the idling operation is improved and more stable idling operation can be achieved.

[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 flowchart showing a conventional idle rotation speed control method for an internal combustion engine according to the present invention. Fig. 4 is a block diagram showing the relationship between the control input/output and the engine in Fig. 3, and Fig. 5 is a block diagram of the control device realized.
6 is a flowchart explaining the control method according to the present invention, FIGS. 7A and B are diagrams showing experimental results of transient response to air conditioner load, and FIG. 8 is a diagram showing details of the integral + gain block. FIGS. 9A and 9B are diagrams showing the experimental results of the transient response to the power steering load, and FIGS. 9A and 9B are diagrams showing the experimental results of the transient response to the clutch load. 1...AAC valve, 2...VCM 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 ... Internal combustion engine (controlled object), 13 ... Condition observation device, 14
... Integral operation + gain block, N _r ... Target value of idle rotation speed, N ... Actual value of idle rotation speed, N _a ... Reference setting value of idle rotation speed,
SA...Difference between the target value and actual value of idle rotation speed, P _A ...Driving pulse width of the control solenoid that defines the amount of bypass air, IT...Ignition timing, x _i ...
State variable quantity, x^ _i ...Estimated quantity of state variable.

Claims (1)

[Scope of Claims] 1. Based on a dynamic model of the internal combustion engine stored in a controller, the amount of air supplied to the internal combustion engine, which is a control input value for the internal combustion engine, or the amount equivalent to the amount of air, and the internal combustion Any one or any two or more selected from the ignition timing of the engine, the amount of fuel supplied to the internal combustion engine, or an amount equivalent to the amount of fuel supplied, and the amount of exhaust gas recirculation, or the amount equivalent to the amount of exhaust gas recirculation. From the combination and the idle rotational speed, which is the control output value of the internal combustion engine, a state variable quantity X _i (i=1, 2, . . . ) of an appropriate order that represents the dynamic internal state of the internal combustion engine is determined.
n), and the estimated state variable quantity x^ _i (i=
1, 2,...n) and the target value of idle rotation speed
In the method of feedback controlling the idle rotation speed of the internal combustion engine by determining the control input value from _Nr and the integral of the deviation SA of the actual value N, a load disturbance that can be predicted in advance from a steady idle state is determined. 1. A method for controlling an idle rotation speed of an internal combustion engine, characterized in that, when a disturbance occurs, feedforward control is performed in response to the disturbance. 2. The method according to claim 1, wherein the feedforward control method is such that a constant value is added to the control input value obtained from the state estimated when a load disturbance occurs. 3. The method according to claim 1, wherein the value to be added to the control input value obtained from the state estimated in the feed forward control is determined based on the engine rotation speed from the time when the load disturbance occurs. .