JPH02139490A - Control of basis weight profile - Google Patents

Abstract

PURPOSE:To shorten the converging time of the standard deviation of a basis weight profile to a target value by bringing a filter constant for the basis weight profile measurement value of a transient time made close to a specific value compared with a stationary time mode. CONSTITUTION:A control mode is divided into two modes comprising a transient time mode and a stationary time mode and a filter constant for basis weight profile measurement values is switched into a value near to 1 in the transient time mode is comparison with the stationary time mode to speed up the response of the control to the change of the profile. When the standard deviation 2sigma of the basis weight profile is within a target value, the transient time mode is switched into the stationary time mode.

Description

DETAILED DESCRIPTION OF THE INVENTION <Field of Application in Industry> The present invention relates to improving the controllability of basis weight profile control.

<Conventional technology> An overview of the papermaking process will be explained with reference to FIG.

Raw material pulp P is seed 21. It joins with the return raw material from the white water silo 3 through the seeding valve 2 and is supplied to the head box 5 by the pump 4. The raw material in the head box is discharged in a sheet form from the gap in the slicing lip 6 onto the wire part 8, is squeezed out by the press part 9, and is transferred to the dry part 1.
After being heated and dried with steam at 0, the product is passed through a calendar 11 and rolled into a roll 12 to become a product. 7 is a plurality of (for example, 60) slice bolts for manipulating the gap between the slice lips.

13 scans the product in the paper width direction to determine the basis weight of the paper (1 m2
This is a B/M meter that measures the weight (weight) and moisture content, and based on these measured values, the absolute dry burial profile of the paper is calculated by dividing the width of the paper into a plurality of points, for example, 360 points.

Absolutely dry weighing pan profile measurement value P at each point determined by calculation
The difference between and the setting rtiS is controlled and calculated by the profile control device 14, and the rig opening degree is adjusted by operating the slice bolt 7 corresponding to the measurement point using the operation output MV, and the absolute dry basis weight profile of the product is adjusted to the set absolute dry. Feedback control is performed to match the basis weight profile.

15 is a man-machine interface that communicates with the control device 14 and has a profile display function.

FIG. 6 shows the upstream fl! of paper 16! II slice bolt and downstream a! For example, 6
36 for 0 slice bolts 7.72...76o
The zero measurement points PV1, PV2...PV360 correspond.

The measured value corresponding to the operation end of the slice bolt 71 is the average value of the six measured values pv, pv...P V 6 ")
Vl is used, and this measured value and one of the profile settings
The slice bolt 71 is operated by the operation output obtained by controlling and calculating the fJ difference. The operation of other slice bolts is similar.

The example in Figure 6 is a 60-point profile method in which multiple measurement points are mechanically associated with specific slice bolts and the average value of the multiple measurement points is calculated, whereas Figure 7 is based on the slice-corresponding profile method. , which shows a general method for determining the range concavity of the measurement points included in the i-th slice, and first calculates the a111 fixed point PVi corresponding to the i-th slice using a statistical method (for example, disclosed in Tokusho No. 61-232181). ), etc., and three measurement points are determined symmetrically on both sides of this slice. Therefore, the number of measurement points included in a book slice bolt is 2n +1, which is always an odd number.

Figure 8 shows an example of the results of profile control with such a configuration, where (A) shows a slice bolt of 7.72 mm.
...Position of 76o, profile setting value S■, measured value f
) shows the relationship of the profile P I” connecting V, and (F
3) is the operation output MV1. to each slice bolt. MV2・
...Indicates the amount of operation of M V eo.

The paper is flowing at a speed of 400 to 10,001 per minute, and the B/M meter, which is a sensor, is flowing at a speed of 5 to 10 per minute in the paper width direction.
Since the speed is n, smoothing processing (filtering) is performed on the JIJ constant data in the flow direction (time series).

When operating conditions change when starting paper production or changing paper types, the deviation increases overall and the basis weight profile deteriorates. Conventionally, in such cases, the operator operated manually and switched to automatic control when the 2σ value (twice the standard deviation of the profile deviation) became small to a certain extent.

The conventional control method uses a distribution control method based on sample PI, and its outline will be explained with reference to the functional block diagram shown in FIG.

17 is a filtering processing function in the flow direction of the profile measurement value, and 18 is a one-way difference calculation function for each slice, which calculates the filtered measurement value PV and the setting profile S.
The deviation of V is calculated for each measurement point, and the surface difference signals for each measurement point are processed for each corresponding slice, and the 1 x difference e for each slice is calculated.
Calculate. For example, there are 40 slices and 360 measurement points.
In the case of points, the deviation e is calculated as the average of nine measurement points corresponding to each slice.

Reference numeral 19 is a nonlinear processing function for the surface difference, which executes processing to zero the deviation for deviations greater than a certain value, and enlargement processing to provide a gain depending on the magnitude of deviations greater than a certain value, and controls the control surface difference E. Send.

Reference numeral 20 has a velocity type PI calculation function, performs proportional and integral calculations on the control surface difference E, and transmits a speed type operation output ΔU.

Reference numeral 21 denotes a distribution calculation function R, which multiplies ΔU by a coefficient and outputs a distributed operation output ΔU' to adjacent slices based on the interference waveform of the slice.

FIG. 10 is an interference waveform diagram for the patent slice characterized by the first slice, and the distribution coefficients αi+2 to αi−2 to the two slices before and after the self are the response values b1+2 to bi of each slice due to interference. −2, α = b,. 2/Δ 1+2 a , 1= b ,, /A α = b, /Δ lχ・ = b1-1/Δ cxi-2=bi-2/l″ Here, Δ=l b1+2 l +l b, .11+
bMo1b, =lbi-2.

Using the distribution coefficient calculated in this way, the operation output ΔLJ' to each slice is as follows: ΔLJ'=α ・ΔU +αi+1 ・ΔLZ+1
++2 ++2 10 α, ・ΔLJ +α, ・ΔLJ,.

+α ・ΔU1-2 becomes.

Reference numeral 22 denotes an output check function, which executes opening degree limit limiting processing between slices on the operation output after the distribution calculation and outputs it to the process, that is, the slice bolt.

<Problems to be Solved by the Invention> The conventional control method uses one mode of distribution control as described above, and when it comes to tuning, priority is given to stable control with no hunting and less overshading. There are the following problems.

(1) Since the flow direction filtering process of the measured value processing has one filter constant, it is a large constant that sufficiently suppresses flow direction fluctuations, and the response to changes in the profile becomes slow.

(2) Since there is only one type of PI control parameter and control cycle,
If there is a large difference in the profile surface after starting paper production or changing the product type, it will take time to converge6.Therefore, manual adjustments are made by the operator, which places a heavy burden on the operator.

An object of the present invention is to provide a basis weight profile control method that can solve these problems.

Means for Solving the Problems> The first feature of the method of the present invention is that the control mode is divided into a control mode when the basis weight profile is defective (hereinafter referred to as transition period mode) and a control mode when the basis weight profile is within the target range (hereinafter referred to as transition period mode). 2 modes (steady mode) and 17, basis weight profile of transient mode? The point is that the filter constant for the J+++ constant value is brought closer to 1 compared to the steady mode.

The second feature is that the control period, proportional gain, and integral gain are changed depending on the transient mode and steady mode.

The third feature is that in the transient mode, sample PI control with a dead zone is used, and in the steady mode, control is performed using a distribution control method based on sample P■.

The fourth feature is that the transition mode is switched to the steady mode automatically when the standard surface difference 2σ of the basis weight profile falls within the target value, or manually at the discretion of the operator. be.

Effects> According to the present invention, there are two control modes: a control mode when the basis weight profile is defective (transition mode), and a control mode when the basis weight profile is in the target range (steady mode).

In the transient tan mode, the filter constant for the basis weight profile measurement is switched to a value closer to 1 compared to the steady state mode.

The control period proportional gain and integral gain are switched and changed depending on the transient mode and steady state mode.

In the transient mode, the sample PI control with a dead zone is executed, and in the steady mode, the control method is switched so that the distribution control method based on the sample PI is executed.

Switching from the transient mode to the steady mode is performed automatically when the standard surface difference 2σ of the basis weight profile falls within the target value, or manually at the discretion of the operator.

<Embodiment> Prior to explaining the functional configuration of the embodiment, the features of the control method of the present invention will be explained.

(1) There are two control modes: 1, a control mode when the basis weight profile is poor (transient mode), and a control mode when the basis weight profile is within the target range (steady mode). Change the following points.

■...Switch the filter constant for the basis weight profile measurement value to a value that approaches 1 relative to the steady mode.

That is, when the filter constant α in the steady state mode and the filter constant α' in the transient mode are set, the following processing is executed: Y - α'. Here, 0$α≦α′, Xo is the measured value, and Y is the measured value after filter link processing.

■...In the transient mode, the control cycle is made earlier than in the steady mode.

As shown in Figure 2, in the steady mode, the control cycle is once every 3 scans of the B/M meter, as shown in (B).
In the excessive mode, this is done every scan as shown in (A) to prevent hunting.

■...Sample P T with dead zone in transition period mode
Control is executed. At the same time, the proportional gain and integral gain are also switched to values that quickly converge even if there is a slight overshoot. That is, the sample PI control calculation is ΔU=K f (E −E ), −E,
) P n nl . Here, K is the proportional gain, KT is the integral gain, E is the current control deviation, and n-1 is the previous control deviation.

FIG. 3 is an explanatory diagram regarding the dead zone processing for a difference of 1, in which dead zones I and 8 are provided in the positive and negative directions with respect to the input surface difference e, and the following process is executed.

In the steady state mode, the control method is switched so that the distribution control method based on the sample PI described in FIG. 9 is executed.

(2) Switching of control mode■...Switching to excessive mode is performed only when the operator switches it.

(2) Switching from the transient mode to the steady mode is done automatically when the operator switches or when the deviation 2σ becomes less than the target value.

FIG. 1 shows a functional block diagram of a control device to which such a control method is applied in the transient mode.

Elements that are the same as those explained in FIG. 9 are given the same numbers and their explanations are omitted, and explanations of elements specific to the excessive mode will be added.

Regarding the flow direction filtering processing function 17, the filter constant is changed as described above, and the control period that regulates the entire control device is also changed.

24 is a dead band processing function for deviation, which is explained in FIG.
Replaces the conventional nonlinearization processing function.

The velocity type PI calculation function 20 is set to the sample value PI control mode, and the proportional and integral gains are also changed.

The distribution processing conventionally performed on control calculation outputs is not performed in the transient mode.

FIG. 4 is a flowchart 1 diagram showing the procedure of signal processing related to control mode switching. 2σ is compared with the 11 target value, and if it is less than the target value, the mode becomes steady control mode.6 If 2σ is greater than the target value, the operator's switching history of the transient mode l\ is checked in step If the switch is switched, the steady mode control is executed as it is, and if the switch is made, the transient mode control is continued.

The application example of the present invention apparatus described above is aimed at controlling the paper profile in the papermaking process, but the following other application examples and modified embodiments are possible.

(1) The same method can be applied to paper thickness profile control, moisture content profile control, and film thickness profile control.

(2) As a control method for the transient mode, the flow direction filter constant, control period, dead zone, proportional gain, and integral gain are changed as a distribution control method similar to the steady mode.

(3) Use not only 2σ but also the maximum value - minimum value of the profile (referred to as R) to determine whether to switch to automatic mode, and use (2σ≦target value) * (R≦target value) as a condition for switching. good.

<Effects of the Invention> As explained above, according to the control method of the present invention, (1)
By switching the control method in transient mode, the surface difference can be reduced by 2σ.
The convergence time to the target value is rapidly reduced.

(2) Since the conventional distribution control, steady-state filter constant, and control gain are used after reaching the equilibrium state, stability and good flux performance are maintained as before.

(3) Even after starting paper production or changing the product type, the excessive control mode allows the profile HSJ B to be quickly set in the automatic control state.
Therefore, the burden on the operator is greatly reduced.

[Brief explanation of the drawing]

Fig. 1 is a functional block diagram showing the transient mode configuration of a control device to which the method of the present invention is applied, Fig. 2 is an explanatory diagram regarding control cycle switching, Fig. 3 is an explanatory diagram regarding deviation dead band processing, and Fig. 4 is an explanatory diagram regarding control mode. Signal processing related to switching 1'In
Figure 5 is an explanatory diagram of the paper machine process, Figure 6 is an explanatory diagram of the correspondence between slices and measurement points using the 60-point profile method, and Figure 7 is the correspondence of measurement points to specific slices in the slice correspondence profile. explanation,
FIG. 8 is a characteristic diagram showing the relationship between the operation amount and profile for slices, FIG. 9 is a functional block diagram of a conventional distribution control device, and FIG. 10 is an interference waveform diagram of a slice lip. 17... Flow direction filtering processing function, 18...
・Penalty difference calculation R function for each slice, 20... Speed type PI
Arithmetic function, 22... Output processing check function, 23...
・Process, 24...Dead zone processing function for surface difference △ ■ ■

Claims (4)

[Claims] (1) There are two control modes: a control mode when the basis weight profile is poor (hereinafter referred to as transition period mode) and a control mode when the basis weight profile is within the target range (hereinafter referred to as steady mode),
A basis weight profile control method characterized by bringing a filter constant for a basis weight profile measurement value in a transient mode closer to 1 as compared to a steady mode. (2) The basis weight profile control method according to claim (1), characterized in that the control period, proportional gain, and integral gain are changed depending on the transient mode and steady state mode. (3) The basis weight profile control method according to claim (1), characterized in that in the transient mode, sample PI control is performed with a dead zone, and in the steady mode, control is performed using a distribution control method based on the sample PI. . (4) A patent characterized in that switching from the transient mode to the steady mode is performed automatically when the standard deviation 2σ of the basis weight profile falls within the target value, or manually at the operator's discretion. A basis weight profile control method according to claim (1).