JPH03164550A - Idling control method of engine - Google Patents

Abstract

PURPOSE:To facilitate setting of a control parameter by obtaining pitch differ ence, at a certain input time, for reducing a specified evaluation function obtained from the predictive and target engine speeds to a minimum, and com puting control input at the present time according to the obtained pitch differ ence. CONSTITUTION:A predictive range N2 is set, as well as an input pitch number Nu not exceeding N2 is set. The predictive engine speed in case of input being changed stepwise between the present time (t) and the future time t+1, t+2...t+N2 in a discrete-time region is computed from a mathematical model indicating the dynamic characteristic of an engine to be set as y(t+1), y(t+2)...y (t+N2). The target engine speed at each time is further set as r(t+1), r(t+2)...r(t +N2), and an evaluation function J to a control characteristic parameter W is computed by an equation I from a pitch difference Du(t) at each input time and the predictive and target engine speeds. The pitch difference Du(t) for reducing this evaluation function J to a minimum is then computed to be used for computing control input at the present time.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an idling control method for controlling the no-load operating rotation speed of an engine to a target value.

[Prior Art] Conventionally, engine idling control has been performed using the P
This was done by ID control.

That is, Kp and K are constants for the deviation between the target rotation speed and the measured rotation speed, the integral value of the pitch difference, and the differential value of the deviation, respectively.
The manipulated variable was obtained by adding a proportional term, an integral term, and a differential term multiplied by i and Kd [Problem to be solved by the invention] According to the above PID control, the control parameters Kp,
There is no Ki and Kd stage setting guideline, so overshoot and vibration are likely to occur.

The present invention is a control method made to solve the above-mentioned problems, and an object of the present invention is to provide an engine idling control method that achieves both coordination and stability and allows easy setting of control parameters.

[Means for Solving the Problem] The engine idling control method of the present invention is a control method for controlling the no-load operating rotation speed of the engine to a target value, in which a prediction range N2 is set as a positive integer, and N2 is set as a positive integer. Set the input step number N, which is a positive integer that does not exceed, and move from the current time t to the future time t+1 . t+2
...Up to t+N2, the inputs are u (t), u (
Calculate the predicted rotational speed of the engine when it changes in a step-like manner as t±1 > -11 (t+N, -1) from a mathematical model representing the dynamic characteristics of the engine, and calculate y (t+
1), y (t+2)...y (t + N 2
), and the target rotational speed at each point is r (t+
1), r (t+2)...r(t+-N2), and the step difference at each point of input is Du (t) = u (t)
=u (t-1), Du(±1) =u (t+
1) -u(t), -Du(t+Nu-
1) zu (t + N u 1 ) u
(Set t+N, -21, and calculate the arbitrarily determined control characteristic variation and add it to u(t-1) to calculate the current operating amount u (t), and control the engine with that operating amount. be.

Furthermore, in the engine idling control method described above,
The input operation amount is the air flow rate.

To specifically illustrate the above, the appropriately set prediction range N2
Assuming that the input u(t-1> continues within N2 as it is in the range up to
+N2) is calculated.

Also, the time point t=1°2 for unit step input...
, N2 responses are calculated from the mathematical model and gl, g2,...
・If gN2, the step response to Du (t) is g Du (t), g2Du (t) - g
N 2 D u < t ).

Therefore, the predicted output time series vector Y is becomes. However, N5=N2-N, +1.

If we express the above equation as a vector and a coefficient matrix G, we get Y=GxD, it can be written as 10H.

Here, if we set the set value vector as R, the evaluation function J becomes J = [R - (GDu + old door [R (GDu - t - H) 1 W [Du] 1 [Du]. Once, 1 represents transposition.

The first term of the evaluation function is the two-to-sum shown in the shaded area in FIG.

'E3 J to find Du that minimizes J in the above formula
/ a Letting Du = O and solving for Du, Du = [G" G-t-WI ] -'G" [R
-H] is obtained.

However, -1 represents an inverse matrix, and ■ represents a unit matrix.

The required step change is the first element Du(t
), so if we find only Du (t), we get Du (t
)=G, [R−HE. However, G = [100...
[GG+WI]-1G'.

The current manipulated variable u(t) is u(t)=u(t-1)
+Du(t).

Du (t+1) is obtained by shifting the prediction range by one step and repeating the above calculation.

Du (t), Du (t±1) obtained in this way
The engine idling control is performed by...

[Operation] The present invention applies the above control method to engine idling control, but the parameters determining the control characteristics are within the prediction range N2. They are the input step number N1 and the constraint coefficient W.

When W=O, a sharp control is achieved with continuous changes in set point as N 2 increases.

However, when W>0, in order to suppress a sudden jump in the manipulated variable in response to a step-like change in the set point, the increase in N is required to increase the difference by one step D11 in the manipulated variable set within the predicted range. This causes a dispersion phenomenon in the amount of change.

In the case of this control that adopts only the first element of the slant Du, N
=1 may be more sensitive than Nu≧2.

Further, when N,=1, no inverse matrix calculation is required, simplifying the control calculation.

Therefore, by setting N = 1, practical control can be achieved. performance.

Sharp control is obtained when N2=2, and gentle control is obtained when the value is increased, but the difference is larger when the set point is known than when the set point is unknown.

However, N2 needs to be larger than the dead time.

As the value of W increases, the control becomes gentler and the robustness improves.

As mentioned above, the guidelines for selecting control parameters are clear.
Compared to ID$II control, stable control without vibration can be easily achieved.

[Example] Embodiments of the present invention will be described below with reference to the drawings.

The engine used was a GM 2.8L V6° MPI.

Experimental data for step response are not shown in Figure 2.

The input of the plant is the air flow rate (■/S) flowing through the idle speed controller, and the output is the engine speed < rpm
), where the fuel is supplied in proportion to the air flow rate.

The process system transfer function is SL G (S)=Ke /('T'1 S
Junior High School 1) (T2 S+11), and parameters were determined to suit the experiment.

The result = 0.29. L=0.48°T1=0.8.
72=0.1 was obtained.

The target rotation speed, which is the set point, is Orpm when 1=0.
The speed was changed stepwise from 750 rpm to 900 rpm when the near conditioner was activated.

When the near conditioner is activated, a step-like torque load is applied to the output shaft of the engine, and the engine rotational system dynamics at this time is Gd (S) = 100.
/(0, IS+1), and the torque load input at that time is set to 1.

The above transfer function G, (S) is of a continuous time system,
Converting it into a discrete time pulse transfer function using the formula, assuming that there is no dead time and setting N=O, we get G(Z)=(b
Z + b Z + b3) / Z2 (Z + a Z + a 2 ) If the Z transformation of human power and output is represented by U and Y, respectively, then from the above equation, G (Z) = Y / U, Y = a (1 / Z) Y a2(i, /z)
Y+b (1/Z) U+b2 (1/Z) U+b3
(1/Z) 3U Since Z is a 1-step advance symbol, 1/Z means a 1-step lag symbol, and converting the above equation into the time domain, y(t)=-a
y(t-1)-a2y(t-2)+b u (t
1) +b2u (t-2)-1-b3u(t-3) Therefore, the formula for calculating h<t+t> is h(t±1)=-a y(t)-a2y(t-1)+
b u (t)+b u (t-1)shi b 3 u
(t2 -2), y (t), y (t-1) is time t.

Actual output value at t-1, u (t-1), u (t-2
) are inputs at times t-1 and t-2, and if u (t) = u (t-1), then from the above equation h<t
+1) is required.

In the same way, h (t+2), h (tmo 3)...
・ is obtained, and D (t) is obtained from these values and used as the current manipulated variable.

The results of the simulation performed as described above are shown in a graph.

In Figure 3, the sampling period is 1 second, W2O is set, and N2 is 2
．． This is the result of flt appropriate predictive control which was changed to 5.15.

The set point was assumed to be known. As can be seen from this figure, the change in the set point at times 50 and 70 seconds is known, so N2
The larger the value, the more input corresponding to the change will be created from the front. A response from 1=0 to start control corresponds to the case where the set point is unknown.

This rise becomes sharp when N2=2, and as N2 increases, control becomes gradually gentler, but there is no large difference as in the case where the set point is known.

Figure 4 shows the results of optimal predictive control when N2 is fixed at 2 and W is varied as O, 0, 2° 0.5. As can be seen from this figure, as W increases, the Become control. Therefore, robustness is improved when the model does not match the plant.

In this way, by selecting two control parameters, it is possible to set a range from sensitive control to slow control with a high degree of freedom, and when a set point change is known, advance measures can be taken, which is a feature of Ik-appropriate predictive control.

Figure 5 shows the results of PID control when the sampling period is 1 second.The setting conditions are such that the overshoot at the start of the control is within 200 rpm and converges quickly, and the proportional gain is: =6. , integral gain: to, ==1.
2. Differential gain: K d = 0.5 9 As is well known, it is observed that it is difficult to achieve both stability and connectivity.

On the other hand, the results of optimal predictive control (in the case of the present invention) are shown in Figure 6.The control parameters are the same as those shown in Figures 3 and 4, but the change in the set point at the front and rear ends of the disturbance is unknown. And so. When the sampling period is 1 second, N2=2. W2O
Since it is possible to select a high gain such as
Unlike TD control, it is very sensitive. Furthermore, there is almost no overshoot or vibration.

Figure 7 shows the PID when the sampling period is 0.08 seconds.
When compared with FIG. 5, which shows the control results, the stability has been significantly improved.

On the other hand, the results of the fin prediction system (tn<in the case of the present invention) when the sampling period is 0.08 seconds shown in FIG. 8 show almost the same tendency as that in FIG. 6.

As is clear from the above, the performance of PID control is greatly affected by the sampling period, but this is not the case with 'Ik appropriate predictive control.

In the case of PID control, when looking at the output with respect to the number of sampling times, the behavior is hardly affected by the period, therefore,
When viewed on the real time axis, it is estimated that the performance improves as the number of samplings per unit time increases, that is, the cycle becomes shorter.

On the other hand, in I&appropriate predictive control, since the control law depends on the unit step response of the plant, its performance is not greatly affected by the sampling period and exhibits excellent controllability even when the period is long.

[Effects of the Invention] As described above, according to the engine idling control method of the present invention, it is possible to obtain controllability that is less susceptible to the influence of the sampling period, particularly when the period is long.

Moreover, selection of control parameters is easy, and high gain can be set while controlling vibration and overshoot amount.

[Brief explanation of the drawing]

Fig. 1 is a graph showing the input/output relationship in the control of the present invention, Fig. 2 is a graph showing experimental data of the step response of the engine used in the embodiment of the present invention, and Figs. FIG. 5 is a graph showing the results of the optimal predictive control as an example. FIG. 5 is a graph showing the results of the conventional PID control. FIG. 6 is a graph showing the results of the optimal predictive control as an example of the present invention. Figure 7 shows a conventional example of P T DillW.
FIG. 8 is a graph showing the results of optimal predictive control according to an embodiment of the present invention.

Claims (1)

[Claims] 1. In a control method for controlling the no-load operating rotation speed of an engine to a target value, a prediction range N_2 is set as a positive integer, and an input step number N_u is a positive integer not exceeding N_2.
is set, and the input is stepped as u(t), u(t+1)...u(t+N_u-1) from the current time t to the future time t+1, t+2...t+N_2 in the discrete time domain. The predicted rotational speed of the engine when the engine speed changes is calculated from a mathematical model representing the dynamic characteristics of the engine.
(t+1), y(t+2)...y(t+N_2), and the target rotational speed at each time point is r(t+1), r(
t+2)...r(t+N_2), and the step difference at each time point of input is Du(t)=u(t)-u(t-1),
Du(t+1)=u(t+1)−u(t),...Du
(t+N_u-1)=u(t+N_u-1)-u(t+
N_u-2), an arbitrarily determined control characteristic parameter W
For, the evaluation function is J=▲There are mathematical formulas, chemical formulas, tables, etc.▼{r(t+j)
−y(t+j)}＾2+W▲There are mathematical formulas, chemical formulas, tables, etc.▼{Du(t+j−1)}＾2, calculate Du(t) that minimizes the above evaluation function J, and calculate u(t− 1) A method for controlling engine idling, characterized in that a current operating amount u(t) is calculated by adding the current operating amount u(t). 2. The engine idling control method according to claim 1, wherein the input is an air flow rate.