JPH0159394B2 - - Google Patents

Description

[Detailed description of the invention]

<Industrial Application Field> The present invention relates to a method for determining the position of an absolute dry basis weight profile measurement point corresponding to the position of a slice bolt, which is an operating end, in a paper machine control system. <Prior Art> FIG. 1 is a schematic diagram of a papermaking process. Raw material pulp P passes through seed box 1, seed mouth valve 2, and then goes to white water silo 3.
It is combined with the return raw material from the pump 4 and supplied to the head box 5 by the pump 4. The raw material in the head box is discharged in the form of a sheet onto the wire part 8 from the gap between the slice lips 6, is squeezed out in the press part 9, heated and dried with steam in the dry part 10, and then passed through the carekada 11 to the reel 1.
It is wound up into a product. 7 is a plurality of (for example, 40
This is a sliced bolt from the book. 13 is a B/M meter that scans the product in the paper width direction to measure the basis weight (weight of 1 m ² ) and moisture content of the paper, and based on this measurement value, the absolute dry basis weight profile of the paper can be determined. It is calculated by dividing the width direction into multiple points, for example 360 points. The difference between the calculated absolute dry basis weight profile measurement value at each point and the set value is controlled and calculated, and the operating output is used to operate the slice bolt corresponding to the measurement point to adjust the lip opening. Feedback control is performed so that the basis weight profile matches the set bone dry basis weight profile. <Problems to be solved by the invention> In the conventional absolute dry basis weight profile control system,
As shown in Fig. 5, the raw material discharged from the head box 5 through the lip immediately jumps out from the head box, flows straight on the wire, and shrinks uniformly during the drying stage. The bone dry basis weight profile is controlled by operating the slice bolts at the corresponding positions. However, in reality, the raw material is not always discharged from the head box immediately, nor does it flow straight. Also, the shrinkage rate is greater near the paper edges than in the center. As described above, if there is a large misalignment between the actual measurement point and the position of the operating end, an undesirable profile sawtooth wave may be generated in absolute dry basis weight profile control. An object of the present invention is to provide a method for determining the measurement point of a B/M meter corresponding to each slice bolt through a test before the start of product manufacturing. <Means for Solving the Problems> The feature of the method of the present invention is that the reference value x _i of the absolute dry basis weight profile measurement points at multiple points in the width direction of the paper before operating the slice bolt is determined, and the k-th slice bolt is operated. N until the after-dry basis weight profile change converges
Regarding the absolute dry basis weight profile measurement data y _i (j),

[Formula] is determined, and i, where this value is maximum, is regarded as the absolute dry basis weight profile measurement point corresponding to the k-th sliced bolt. <Operation> According to the present invention, first, the reference value of the absolute dry basis weight profile before operating the slice bolt is determined, and then, when a certain slice bolt is operated, the measurement value of the absolute dry basis weight profile is determined until the change in the measured value of the absolute dry basis weight profile converges. The data for each measurement point was obtained for multiple scans, and the square root value (hereinafter referred to as RMS) of the difference between the data at a certain measurement point and the reference value was calculated for the multiple scans, and the measurement point with the largest value was operated. Regarded as a measurement point corresponding to a sliced bolt. <Example> The procedure of the method of the present invention will be explained based on FIG. In the step, the bone dry basis weight profile data before the slicing bolt operation is measured for multiple scans, and in the step, a time-series average calculation is performed for each measurement point on the measured data to obtain the reference value x _i of each measurement point. is required. Next, the step slice bolts are operated sequentially starting from No. 1, and bone dry basis weight profile measurement data y _i (j) for multiple scans are collected in steps for each slice bolt operation until the change in bone dry basis weight profile converges. be done. After the change in the absolute dry basis weight profile converges, the RMS of the change is calculated for each measurement point in the width direction using the data in the step. In the step, the measurement point i with the maximum RMS is determined, and in the step, the center position of the control deviation calculation is corrected so that the position of the k-th slice bolt matches the measurement point i. FIG. 2 is a flowchart showing the signal processing procedure of FIG. 1, and the processing from step to step is executed for all slice bolts. Next, an example of the processing contents of each step will be explained.
Figure 3 shows the input data for the bone dry basis weight profile in the step x ₁ , x ₂ , x ₃ ...x _i ...X ₃₆₀
is the absolute dry basis weight profile measurement value of 360 measurement points. In this step, the measured values for multiple scans are input and a time-series average calculation is performed for each measurement point. For example, assume that corner measurement point data at times t ₁ , t ₂ , and t ₃ are collected as follows. (1) x ₁ (t ₁ ), x ₂ (t ₁ )…x _i (t ₁ )…x ₃₆₀ (t ₁ ) (2) x ₁ (t ₂ ), x ₂ (t ₂ )…x _i ( t ₂ )...x ₃₆₀ (t ₂ ) (3) x ₁ (t ₃ ), x ₂ (t ₃ )...x _i (t ₃ )...x ₃₆₀ (t ₃ ) The time series average _i of measurement point i is , _i = {x _i (t ₁ ) + x _i (t ₁ ) + x _i (t ₁ )}/3. This time series average is calculated for all 360 points. Note that the reference value is the measurement data x _i obtained by one scan without taking the time series average as described above
You can also find it by Next, it is assumed that the measurement data of the absolute dry basis weight profile of N scans is collected as follows until the change in the absolute dry basis weight profile converges after operating the k-th slice bolt. (1) y ₁ (1), y ₂ (1),…y _i (1)…y ₃₆₀ (1) (1) y ₁ (2), y ₂ (2),…y _i (2)…y ₃₆₀ (2) ( ) y ₁ (N), y ₂ (N),...y _i (N)...y ₃₆₀ (N) In the step, the RMS of the change at each measurement point is calculated based on this data. Letting the i-th RMS be R _i ,

[Formula] In the step, the maximum RMS measurement point is found. For example, if R ₁₅₀ is the maximum when operating slice bolt No. 10, then slice bolt No. 10 is
It is recognized that the corresponding measurement point for the number is 150,
In this step, correction is performed using this point as the center point of control deviation calculation. Production begins after determining the corresponding measurement points for all sliced bolts. <Effects of the Invention> As explained above, according to the present invention, it is possible to determine the corresponding positional relationship between the operating end and the measuring point in the papermaking process where the operating end and the measuring point are far apart and the state of the object to be measured changes during the process. It can be determined with high accuracy, it is possible to suppress the sawtooth wave of the profile caused by the deviation in the positional relationship, and it is possible to significantly improve the controllability of bone dry basis weight profile control.

[Brief explanation of drawings]

1 and 2 are block diagrams and flowcharts showing the signal processing procedure of the method of the present invention, FIG. 3 is an explanatory diagram showing an example of measurement data of bone dry basis weight profile, and FIG. 4 5 is a schematic diagram of the papermaking process, and FIG. 5 is an explanatory diagram showing the relationship between the operating end and the measurement point. 1... Seed box, 2... Seed mouth valve, 3... White water silo, 4... Pump, 5... Head box, 6...
...Slice lip, 7...Slice bolt, 8...
...Wire part, 9...Press part, 10...
...Dry part, 11...Calendar, 12...
Reel, 13...B/M total.

Claims (1)

[Claims] 1. A reference value x _i of a plurality of absolute dry basis weight profile measurement points in the paper width direction before operating the slice bolt is determined, and after operating the kth slice bolt, the absolute dry basis weight profile change converges. For the N dry basis weight profile measurement data y _i (j) up to N times, find [Formula] and consider i, where this value is the maximum, as the bone dry basis weight profile measurement point corresponding to the k-th slice bolt. A method for determining absolute dry basis weight profile measurement points.