JPH0637758B2 - Profile control device - Google Patents

Description

TECHNICAL FIELD The present invention relates to robust control of a profile and prevention of divergence of the control in a basis weight profile control process.

<Prior Art> An outline of a papermaking process will be described with reference to FIG. The raw material pulp P merges with the return raw material from the white water silo 3 through the seed box 1 and the seed 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 of the slice lip 6 onto the wire part 8, squeezed by the press part 9, heated and dried by steam in the dry part 10, and then passed through a calendar 11 and reel 12. It is rolled up into a product. Reference numeral 7 is a plurality of (for example, 60) slice bolts for operating the gap of the slice lip.

No. 13 scans the product in the paper width direction, and the basis weight of the paper (1 m ²
Is a B / M meter for measuring the water content) and the moisture content, and the absolute dry basis weight profile of the paper is calculated based on the measured values by dividing the lateral width direction of the paper into a plurality of points, for example, 360 points.

Absolute dry basis weight profile measured value PV of each point calculated
The difference between the set value SV and the set value SV is control-calculated by the profile control device 14, and the slice opening 7 corresponding to the measurement point is operated by the operation output MV to adjust the lip opening, and the absolute dry basis weight profile of the product is set to the absolute dry value. Feedback control is performed so as to match the basis weight profile.

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

Figure 5 is intended to show the relationship of measurement points upstream of the slice bolt and the downstream side in the sheet 16, for example, 60 pieces of sliced bolts 7 _1, 7 ₂ ... 7 ₆₀ The measurement points 360 points P
V _1, PV ₂ ... PV ₃₆₀ correspond.

The measured value corresponding to the operating end of the slice bolt 7 ₁ is an average value of ₆ measured values PV ₁ , PV ₂ ... PV ₆ . Is used, and the slice bolt 7 ₁ is operated with the operation output obtained by controlling and calculating the deviation between the measured value and the set value of the profile. The operation of other slice bolts is similar.

The example of FIG. 5 is a 60-point profile method in which a plurality of measurement points are mechanically associated with specific slice bolts and the average value of the plurality of measurement points is calculated. , A general method of determining the range of the measurement points included in the i-th slice, and the measurement point PV _i corresponding to the i-th slice is first disclosed by a statistical method (for example, disclosed in Japanese Patent Application No. 61-232181). ) Or the like, and it is determined so as to include n measurement points symmetrically on both sides of this slice. Therefore, the number of measurement points included in one slice bolt is 2n + 1, which is always an odd number.

FIG. 7 shows an example of the result of profile control by such a configuration. (A) shows slice bolts 7 ₁ , 7 ₂ ...
7 shows the relationship between the position of _60, the profile set value SV, and the profile PF that connects the measured value PV, and (B) shows the manipulated variables of the manipulation outputs MV ₁ , MV ₂ ... MV ₆₀ to each slice bolt.

Next, the profile control algorithm first executes non-linearization processing on the deviation for each slice, executes PI control calculation on the processing output, and outputs the distribution coefficient based on the interference waveform of the slice to the calculation output. Distribution processing for multiplication is executed, smoothing processing is further executed, and an operation output to the slice bolt is transmitted.

<Problems to be Solved by the Invention> In the grammage profile control as described above, due to the problems described below, an error occurs in the control system, and there is a tendency for divergence.

(1) Since the distance between the operation end and the measurement point is more than 200 m, and the paper contracts or meanders between them,
It is difficult to accurately correspond between the operating end and the measurement conversion.

(2) Since the place to operate is a fluid-like place before turning into paper, the interference waveform is not smooth as in FIG. 8 (A), but complicated as in (B) including noise. And the distribution process is not executed properly.

(3) When the type of paper is changed, the weight of the paper and the speed of the paper machine are changed, so that the correspondence of the positions and the interference are changed.

The error generated in the control system first acts to improve the profile, but if the control is not accurate, the profile diverges in a sawtooth shape from the middle.

In the conventional control, it was not checked whether the profile was an improvement tendency or a divergence tendency and a control method corresponding to it was not executed.

An object of the present invention is to provide a profile control device capable of solving such a problem.

<Means for Solving the Problems> In the present invention that achieves such an object, a 2-sigma calculator (17) that calculates the standard deviation of the deviation of the profile measurement value (PV) from the set value (SV) for each measurement cycle. ) And this 2
A moving average processing unit (18) for taking a moving average of the standard deviation calculated by the sigma calculation unit for a predetermined number (m) of control cycles.
And the difference between the moving average standard deviation of this time calculated by this moving average processing unit and the moving average standard deviation of the previous time (hereinafter referred to as “improvement rate”), and this improvement rate and a preset dead zone set value. When the absolute value of the improvement rate is smaller than the dead zone set value, zero is output, and in the case of the remainder, the improvement rate calculation unit (19) that outputs the improvement rate and the improvement rate calculation unit When the output value is zero for a preset number of times consecutively, or when the output improvement rate is negative and when the current moving average standard deviation exceeds the preset standard deviation target value Is provided with a comprehensive determination unit (20) for stopping the operation output.

<Operation> According to the invention having such a configuration, the standard deviation relating to the deviation between the profile measurement value and the set value in the current measurement cycle is calculated by the 2-sigma calculation section, and the moving average processing section calculates the standard deviation about several times. The noise components are removed by averaging. Then, the improvement rate calculation unit sets the improvement rate to zero within a certain dead zone range. When the improvement rate is zero for a certain number of times in succession, when the improvement rate is negative, and when the standard deviation of the moving average exceeds a predetermined value, the operation output is stopped and the control state becomes unstable. Prevent the papermaking process from deviating from the control target.

<Embodiment> Firstly, the function related to the present invention provided in the control device 14
This will be described with reference to the functional block diagram in the figure.

Reference numeral 17 is a 2σ calculation unit of the deviation of each measurement point of the measurement profile PV and the setting profile, 18 is a moving average processing unit of 2σ, 19 is an improvement rate processing unit, 20 is a dead zone setting function for this improvement rate processing unit, 21 Is a comprehensive determination unit, which receives the output of the improvement rate calculation unit, the output of the 2σ target value setting function 22, and the output of the number of times improvement rate zero setting function 23, and outputs an output signal C.

By this output signal C, control is stopped, control calculation is continued,
Sequences such as restart of control calculation, abnormal signal and control stop are executed.

Next, the operation of each functional block will be described with reference to the flow chart of FIG. 2 and the profile characteristic diagram of FIG.

As shown in FIG. 3, the measurement value at the i-th measurement point in the number of measurement points n is x _i , and the set value is y _i .

After the start, in step (1), the deviation (x
_i− y _i ) is calculated, and in step (2), the 2σ calculation unit 1
7, the standard deviation 2σ is Is calculated for each measurement cycle.

2σ of the measurement cycle this time is 2σ _k , and 2σ before the last time is 2
Let σ _k-1 , 2σ _k-2 .

In step (3), the moving average unit 18 calculates the moving average of this time. But, Calculated by Here, m is the number of objects of the moving average.

In step (4), the improvement rate calculation unit 19 calculates the moving average of this time. And the previous moving average Difference S of It is calculated by, and this is taken as the improvement rate.

In step (5), Step (6), the S absolute value when larger than h _ys improvement rate S in comparison to the improved ratio S and deadband setting value h _ys, and outputs a zero when less than h _ys The process is executed.

That is, The output process of is executed.

Steps (7) to (13) are the judgment contents of the comprehensive judgment unit 21. First, in step (7), the target value is compared with 2σ, and if the target value is less than or equal to the target value, the control suspension is checked in step (8). If it is not suspended, the improvement rate S is not a negative value in step (9). It is confirmed that the improvement rate of zero is not continued for a certain number of times or more in step (10), and an output signal for continuing the control is transmitted.

When the control is suspended in step (8), it is determined that the improvement rate S is a negative value in step (9), and that the improvement rate zero continues for a certain number of times or more in step (10). A pause output signal is emitted.

In step (7), 2σ is compared with the target value, and if it is equal to or larger than the target value, the control suspension is checked in step (11).
If it is not at rest, it is confirmed in step (12) that the improvement rate S is not a negative value, and it is further confirmed in step (13) that the improvement rate zero has not continued for a certain number of times or more, and the control continuation output signal. Is sent.

If the control is suspended in step (11), step (1
If the improvement rate S is a negative value in 2), step (13)
When it is determined that the improvement rate of zero has continued for a certain number of times or more, an abnormal alarm and an output signal of control stop are transmitted.

If the control is not suspended in step (11), an output signal for instructing the resumption of control is transmitted.

The application example of the present invention described above is intended for the profile control of the paper in the papermaking process, but is also applied to the profile control of the paper thickness, the moisture content profile control, and the film thickness profile control in the same manner. It is possible to

<Effects of the Invention> As described above, according to the present invention, (1) a process for quickly detecting a divergence tendency of control caused by a rush of an actual process and a control system due to a change in operating conditions and preventing divergence. Can be executed.

(2) Since the control is stopped when the improvement of the profile by the control stops or reverses, the operating end is not moved excessively.

This has the effect of prolonging the service life particularly in the case of an operating end using a motor.

[Brief description of drawings]

FIG. 1 is a functional block diagram showing an embodiment of a control device to which the present invention is applied, FIG. 2 is a flow chart for explaining the operation, FIG. 3 is an explanatory diagram of deviation calculation, and FIG. FIG. 5 is an explanatory diagram of the paper machine process, FIG. 5 is an explanatory diagram of correspondence between slices and measurement points by the 60-point profile method, FIG. 6 is an explanatory diagram of correspondence of measurement points to specific slices in the slice correspondence profile, and FIG. 7 is slices. Fig. 8 is a characteristic diagram showing the relationship between the manipulated variable and the profile for Fig. 8, and Fig. 8 is an explanatory diagram of a slice lip interference waveform diagram. 17 ... 2σ calculation unit, 18 ... Moving average processing unit, 19 ...
… Improvement rate calculator, 20 …… Improvement rate dead zone setting function, 21
...... Comprehensive judgment part, 22 ...... 2σ target value setting function, 23 ・ ・ ・
… Zero improvement rate setting function

Claims (1)

[Claims] 1. A set value (S) of a profile measured value (PV)
V) Calculate the standard deviation of the deviation for each measurement cycle 2
A sigma calculator (17), a moving average processor (18) that calculates a moving average of the standard deviation calculated by the two sigma calculator for a predetermined number (m) of control cycles, and a moving average processor. Also, the difference between the current moving average standard deviation and the previous moving average standard deviation (hereinafter referred to as "improvement rate") is calculated, and this improvement rate is compared with the preset dead zone setting value, and the absolute value of this improvement rate Is smaller than the dead zone set value, zero is output, and in the remaining case, the improvement rate calculation unit (19) that outputs the improvement rate and the value output by the improvement rate calculation unit are set to a preset number of times. When the value is continuously zero, or when the output improvement rate is negative, and when the moving average standard deviation this time exceeds the preset standard deviation target value, the comprehensive determination unit that stops the operation output ( 20) and Profile control device to collect.