FI85518B - Method for simultaneous control of curling and fiber orientation on paper machine - Google Patents

Description

1 85518 1 Method for Simultaneous Adjustment of Curvature and Fiber Orientation on a Paper Machine Förfarande för samtida regiering av krullningen och fiberorienteringen pA en pappersmaskin 5

The invention relates to a method for adjusting the diagonal curvature profile and fiber orientation of paper in paper machines equipped with edge flow channels. The invention makes it possible to control the layered formation mechanism of the fiber structure of the paper and its orientation.

With previously known methods, the tendency of the paper to curl can be controlled on a paper machine by controlling the angle of impact of the jet, arranging the dewatering, the line pressure of the press and the drying section by means of surface temperature differences between the upper and lower cylinders. The setting of the speed difference between the shower and the wire is also an important means of controlling the tendency to curl. All the above methods simultaneously affect the entire width of the paper web .20, so it is impossible to adjust the profiles with these known process variables. The currently known way of influencing the curvature profile is to use a so-called curling irons over which the rollers obtained from the slitter are drawn while adjusting the track tension.

25 With regard to warping, the main drawback of the current practice is to make the paper meet strict quality requirements, e.g. copyability criteria, across the width of the paper path. Often the edge areas of the track have to be sold in cheaper quality. The uneven quality of the paper web in the transverse direction also makes it difficult to cut the customer rolls.

The method according to the invention provides a decisive improvement in the above-mentioned drawbacks. To achieve this, the method according to the invention is characterized by what is stated in the characterizing part of claim 1.

The most important advantages of the invention are that the curvature properties and profiles of the final product can be influenced already at the beginning of the process 2 85518 1 at the source of the errors. This improves the runnability of the machine and thus also has an increasing effect on production volumes. The method can thus improve both quality and productivity.

In the following, the invention will be explained in detail with reference to an embodiment of the invention shown in the figures of the drawing, to which, however, the invention is not narrowly limited.

Figure 1 schematically shows a headbox of a paper machine provided with edge flow channels and a control system according to the invention connected thereto.

Fig. 2 shows the discharge side of the headbox turbulence generator as seen from the direction A drawn in Fig. 15.

Figures 3 show flow charts of a fading program and a control program applicable in the method according to the invention.

. ! Figures 4 illustrate the response run by showing the possible curvature and fiber orientation profiles in state 1 and state 2 and the change profiles calculated from them.

Figures 5 show by way of example the initial curvature and fiber orientation profiles (Figures 5A and 5B), the change profiles obtained from the response tests (Figures 5C and SD), and the expected post-adjustment end state profiles (Figures 5E and 5F).

. Fig. 1 schematically shows a control system according to the invention. An implementation example of the '30 system. In Fig. 1, the headbox feeds a mass jet J onto a planar wire 19 passing over the breast roll 22. The mass flow penen flow originates from the manifold 4 and most of this flow F 1 (so-called headbox flow) passes through the manifold 12 and the equalization chamber 13 to the turbulence generator 14. In addition to the flow Fj, from the manifolds 4, bypasses 23a and 23b in its lower walls, bypasses F # and F1 leave, which are led through bypass pipes 1a, Ib, flow meters 2a, 2b and control valves 3a, 3b to bypass pipes 5a, 5b, which are connected to edge edges 16a and 16b on opposite edges of the turbulence generator 14 li 3 85518 1. The edge grooves 16a, 16b are polygonal in cross-section as seen in Fig. 2, which shows the outlet side 15 of the turbulence generator as seen from the direction A indicated in Fig. 1. Reunasolaa 16a is limited in the horizontal direction 5 of the turbulence generator, a side wall 24a formed in the turbulence generator and the downstream flow tube 25 rectangular step-like wall. In the vertical direction, the edge groove 16a is delimited by the upper wall 26 and the lower wall 27 of the turbulence generator. The edge groove 16b of the opposite edge is formed in a corresponding manner. The pulp jet from the turbulence generator 10 enters the lip channel 17, from where it discharges through the lip opening 18 onto the flat wire 19. The headbox pressure is measured through the edge plate of the lip channel 17. The size of the lip opening is determined by the lower lip bar 20 and the upper lip bar 21.

15 Bypass breaks Fa and controlled by control valves 3a and 3b, respectively. The by-pass volumes in pipes 1a, 5a (= a-side) and Ib, 5b (* b-side) are measured with flow meters 2a and 2b, respectively. The response and control algorithm of the method according to the invention is implemented in a microcomputer 6, which is connected to a connection unit 7 via 28, which in turn have connections 8a and 8b to flow meters 2a and 2b and connections 9a and 9b to control valves 3a and 3b. The signal Qa ° ut (connection 9a) generated by the microcomputer 6 controls the control valve 3a and the signal Qa * n (connection 8a) is information given by the flow meter 2a on the flow rate in the bypass pipes 1a, 5a. The corresponding signals on the b-side are 0 ^ ° ** ^ and in addition to these, connections 10 and 11 are connected to the connection unit 7, through which the microcomputer 6 receives, for example, information from the paper machine process computer or the corresponding headbox average lip setpoint b and headbox pressure setpoint P.

Next, the mathematical basis of the method of the invention is presented and the various steps of the control method according to the invention and the progression of the control algorithm from one step to another are described.

Step 1 Response runs are performed on a paper machine as shown in Figure 3B.

35 Response run means moving a paper machine from state 1 i * p · i to state 2. In the method of the invention, the state of the paper machine is determined. The machine run values (Q, b ^, P ^) and the edge feed values (Qa *, Qjj "), where Q is the total flow volume discharged from the headbox orifice ii 4 85518 1, are the average orifice setpoint, Pj is the headbox pressure setpoint and«. 3 * Ob * are the magnitudes of the edge flows Qa and V, respectively.During the response run, the paper machine run values (Q, b £, Pj) remain constant, 5 but in the change from state 1 to state 2 the edge feeds Qa and «b are changed as desired (either Qa or Qb For the response run, first select the lip opening setpoint b ^ and the headbox pressure setpoint Pj, which also determine the magnitude of Q. Similarly, the desired values Qa * and Oj are set for the edge currents. "· When the paper machine is stabilized, run for laboratory measurements, a test specimen corresponding to space 1. Next, the edge flows are changed as desired: 15 Q.1 - »Q.1 + ÄQa (1) and

Qb “- Qb“ +. (2) where Qa * + AQa i · C + iOi, are the edge currents corresponding to state 2. Once the paper machine has stabilized, run in space 2 experiments.

From the test webs, the curvature profiles K i y) and the fiber orientation profiles h-1,2 corresponding to space 1 and space 2 are measured in the laboratory; the profile refers to the property of the paper measured from the web (in this case the curvature or the -: ‘;‘ 25 tation of the fibers) as a function of the transverse distance y of the paper web.

The profiles are determined by taking 10 ... 15 cross-sectional samples from the machine roll, from each of which the quantity under consideration is measured, e.g. from 15 measuring points at regular intervals. There are several known methods for measuring fiber orientation: Nomuramit-. .30 background, Morgan method, skew strength test and DFS method.

The curvature, in turn, can be determined, for example, by a standard curvature test or by optical distance measurement; of these; * the former is based on the measurement of the curvature of an A4 sheet and .V in the latter the computer measures the surface shape of the test sheet and | 35 calculates the curvature of the surface from it.

Il 5 85518 1 In the following, the notation represented by formulas (1) and (2) is denoted by: (Q, 1, ΔΟ. / Ό AÖb> '5, i.e. this notation means the change in which in the initial situation (state 1) the edge currents are and and then the edge flows are changed simultaneously, the former by the amount of AQa and the latter by the amount of AQ1 to reach the final situation 10 (state 2).

Next, the change profiles are calculated from the measured curvature and fiber torsion profiles: AK (y) = K2 (y) - Κχ (γ) (3) and A © (y) = e2 (y) - © j (y). (4)

Calculating the curvature change profile 20 AK (y) and the fiber orientation change profile A © (y) according to formulas (3) and (4) terminates the execution of one response run. In this response run, it has thus been found that when the run value of the paper machine is (Q, b ^, Pj) and the edge feeds are changed in a way (Qa ^, Qjj * 'AQjj), the resulting profile changes • 25 are AK (y) and A © ( y). In order to improve the statistical significance, several response runs can be driven with the same run values (Q, b ^, Pj) and the same edge flow changes AQ ^), whereby AK (y) and Ad (y) are fitted by mathematical optimization to best match the results of all observed response runs.

For each paper machine run value (Q, b ^, Pj) and Γ initial values of edge flows (0 ^, ¾-) considered, the response runs are performed with several different edge feed changes AQa and AQ | 35 which should be selected to cover the entire available flow range. The initial values of the edge flows (Q *, 0 ^ "), in turn, can be traversed by one or more. In the case of changes in edge flows (Qjj1, AQa 'V' both AQft and 6 85518 1 AQjjJ can be changed simultaneously or kept constant (Δθβ * 0 or ΔΟϊ, = 0) and changes only the second, in the former case going through all the combinations requires nm response runs, while in the latter n + m-1 pieces are used to determine the response times (n 5 is the number of AQa changes and m is the number of AQjj changes).

The use of the latter method is based on the approximation that the sum of the profile changes obtained from the response times (Q, 1, AO ^ / Oj / VO) and AQj,) is the same as the profile change result due to the change (Qa1, AQa; QbB, ΔΟ *,). Underlying the approximation 10 is the observation that changing the edge flow on either side affects the flow over the entire width of the lip opening. If now simultaneously changed into the edge on both sides of the liquid-collapsibility can be expected due to the change of additive from each side edge 15 feeds the flow to one, that is, the overall effect is the same as the sum of both sides of a single change.

For each paper machine run value (Q, b £, Pj) considered and for the initial values of the edge feeds (0 ^, 0 ^ *), the results of the response runs can be illustrated in the form of the following table.

TABLE 1: Example of presenting the results of response times.

.... 25 (Qrb ^ Pj); (Q.1, ^ ·) Δ0 », 1 6¾2 AQb3 30 <ΔΚ, ιΐ'ΔΘ, ιι> (Δκι12, αθ, 12) .....

ΔΟ.2 <ΔΚ, 21 ^ 121 ^ <ΔΚβ22, Δθβ22) .....

ΔΟ.3

Table 1 shows the profile changes AK and ΑΘ, which are calculated by formulas (3) and (4) and are thus functions of the transverse distance '/ • 35 7 85518 1 y, i.e. e.g. ΔΚ ^ ι * ΔΚ (γ) ζ1 ^, the index z is abbreviation for indices i, j, l, m. Depending on how the response times are performed, whether all elements of the table are based on separate response times (making them more accurate) or whether part 5 is obtained in the above approximate way as the sum of two changes (in which case fewer response times survive).

For the application of the control method according to the invention, it is sufficient to make 10 response times for one setpoint of lip opening b and headbox pressure P and for one initial values of edge flows and Of, "· Based on user experience the headbox pressure P, is substantially varied, it may be advantageous to perform response runs with other values of the (b, P) pair as described above.

Before discussing the following steps, which describe the actual implementation of the paper machine adjustment 20, the concepts and mathematical formulas required therein will be reviewed. The adjustable curvature profile measured by the user at baseline is denoted K (y) and the fiber orientation profile is denoted 6 (y). Adding to these profile changes measured in response times, new functions are obtained: - - 25 KD (y; z, p, q) - K (y) + ΔΚ (Υ) ιρ, (5) ®D (y; z, p, q) - ® (y) + A® (y) Bpq, (6) 30 where z is an abbreviation for the indices i, j, l, m, i.e. ^ K (y) Bp ^ and Ae <y) apq are at the paper machine running value (Q, b ^, Pj) measured for the change (Qe *, ΔΟ ^) measured curvature and fiber orientation profile changes, cf. Table 1. The profiles defined by formulas (5) and (6) thus approximate the curvature and fiber orientation -. '. 35 profiles in case the edge currents would be changed by AQaP j * To form the cost function described below, the user of the method of the invention 8 85518 1 should and the fiberization profiles to be comparable with each other and form a figure describing the difference between the modified and the desired profile. One way to accomplish this is as follows: the user defines a maximum allowable 5 (denoted by Κ> βχ) and a minimum allowable curvature (Ka £ n) r maximum allowable (Θ_m ^) and minimum allowable fiber orientation <®.in) and a target value for curl (Ktay) for the paper web. and the target value (θ ^ βν>; these numbers may be constant or change as a function of the web width y. The closer the profile 10 (curvature or fiber orientation profile) to the final state (i.e., the post-adjustment state) is, the closer it is. The difference between these is described by the area between the well-measured profile and the target value obtained mathematically by integration, in which case the co-dimensional reference values for curvature and fiber-15 orientation (K and Θ, respectively) describing the goodness of achieving the target value are obtained from the formulas:

L

K (* rP »q) - J lfK (y) l dy '<7> o where L is the width of the lip jet and 20 f ^ -Ktav ^ Kmax-Ktav» »if KD a Ktay fK (y>“ Λ (8) [iKtav - ^ / iKtav-W '1 ° β »<Ktav ... 25 KD = KO (y; z, p, g) from formula (5), and

L

§ (ZrP »q) J | fθ (y) | dy / (9) 30 o where f 'Jo · eD a et „; ··. fe <y) - <(10) [(et „-eD) / (et„ -e.in), jo. eo <et „.;. 35 6D = 6D (y; z, p, q) from formula (6).

Equations (7) ... (10) are only one way to realize the mutual comparability of curvature and fiber 9 85518 1 orientation and to produce a figure describing the achievement of target profiles. However, the method of the invention is not limited to this particular representation, but the user may apply other formulas as needed: for example, paper web edge strips may be disregarded (by delimiting the integration area) or narrow but large amplitude deviations may be made particularly undesirable (f by changing the weighting factors of the ^ and fQ functions). It is essential to ensure that Jt and Θ are non-negative and that the lower the reference value (K or Θ), the better the quality characteristic of the paper.

It is expected in advance that the minimum possible curvature and the minimum possible fiber orientation will not be achieved simultaneously. Therefore, before beginning the adjustment, the user should decide in which ratio the importance of achieving a small curvature or a small fiber orientation is emphasized. This is determined by the curvature weighting factor r, by means of which the quantities K and Θ are formed into the so-called cost function Z: Z2pq * rK (*, p, q) + (1-r) § (z, p, q), (11) 20 where 0 sr <1. Then, for example, setting r = 1 minimizes only curvature regardless of orientation, and the value r-0.5 is used to obtain a situation in which both curvature and orientation are simultaneously as small as possible, but neither is necessarily at a minimum.

.25

Let us now consider the mass flow from the headbox in general. The total volume flow Q discharged from the headbox lip is: Q * Av, (12) 30 where A is the cross-sectional area of the lip jet at the point where the jet has velocity v. Immediately after the tip strip, the jet velocity is approximately: * *. 2P / d, (13): * · where P is the headbox pressure and d is the mass density. Taking into account the height difference (H / 2) between the pressure measuring point and the jet speed reference point (so-called vena ίο B 5 51 8 1 contracta) as well as various friction etc. dimensionless figures describing the losses and Kc, the following formula is obtained for the jet velocity in the vena contracta: 5 v = CV 2P / d, (14) where the formula for the velocity correction factor C is derived from the literature: 10/1 + (Hb) gd / (2P) c = | I ΓΤ <15> Ί (t) 15 where b is the average lip opening, g is the acceleration due to gravity and ^ is the coefficient of contraction. In practice, the numerical value of the speed correction factor C is very close to one. On the other hand, the cross-sectional area A of the jet in the vena contracta is: 20 A = b-tf L, (16) where L is the width of the lip jet. The volume flow of the lip jet can thus be expressed by the formula -.-: • -25 Q = b-X L C ^ 2P / d. (17)

Since the width L of the lip jet is a paper machine dependent constant and the contraction factor X and the speed correction factor C are kept constant or vary only slightly and the density d changes slowly through temperature 30, it can be deduced from formula (17) that Q depends essentially only on the average lip b and the headbox pressure P. Therefore, in the future, the volume flow Q is presented only as a function of b and P, Q = Q (b, P), but when calculating the value of the function, the the values of C, <K and d prevailing under the conditions may be available.

/.35

The running point (Qo'b0 'P0; ®a °') refers to the running values of the paper machine (i.e. the average lip opening setpoint bg, the headbox pressure setpoint 855 1 8 1 P0 and Q0 * Qo ^ bO'P0 ^ the borehole feed rates (Qa °, Qj, 0) in it in the state (initial state) in which the method according to the invention starts to control the paper machine to minimize the cost function Z. In the future, the driving point is denoted AP for brevity. The response point VPQ »5 (Qn, bn'pn» Qa ° * Qj, n) the edge feed rates with the response runs according to step 1. The distance AVQ between the running gear AP and the response point VPn is defined by the formula: 10 AVn = λ / ci'dl + c2 d2 + c3 d3 + c4d4 'dl = ΠΟθ- ° η> / 0θ12 d2 * KVbn> / b0) 2 15 d3 = l (~ / v /> / V2 d4 = t <lo. ° -0 + 1¾ ° -¾ ^) / Qo 52 · 20 In formula (18) the numbers Cj, c ^, and are standard coefficients that determine the extent to which different factors are taken into account; one possible choice is: Cj = l, ¢ ^ = 1/2, Cj * l / 4 and c ^ = l / 8.

The following steps describe the control part of the method, cf. Figure 3C.

-25

Step 2 To generate the cost function, the user gives the weighting support factor r for the curvature. If r * 1, the input data and profile measurements related to the fiber orientation are not required. The same is true for curvature if r «0 is given.

Step 3 The user gives the target value of the curvature Ν: · ν 3 * the target value of the fiberization ®tav · Also read the figures WK * in '®.a * and θΜ £ η or equivalent values for the formulas developed by the user. . The figures given can also be profiles, i.e. depend on the transverse distance y of the track.

i2 85 5 1 8 1 Step 4 The curvature profile K (y) and the fiber orientation profile 0 (y) corresponding to the current driving point are measured. The results of laboratory measurements are entered into a microcomputer.

5

Step 5 Check if the profiles are already within the desired limits, ie no adjustment is required. No adjustment is required if in case of 10 (i) 0 <r <1: K.in 5 K <y> S K..x 3a ®.in 5 ® <y> 5 θ · »χ 'in case 15 (li) r = 1: In the case of K * in ss Nwx '(iii) r = 0: 20 ®min s ® <y) s ®..x *

If no adjustment is required, the algorithm skips to step 8.

- -.25

Step 6 In this step, it is assumed that only one response point is available VP ^ = (®l'bl'pi * ΔΟ ^ *) · If response runs have been made for two or more response points, the implementation of the algorithm jumps to step 7.

30

From the measured profiles and the response run inputs (step 1), form the functions according to formulas (5) and (6). Using the parameters and formulas (7) ... (11) read in steps 2 and 3, these further give the cost function Z as a function of the edge flow changes AQa / 35 and Δ0 |. According to Table 1, a table corresponding to ‘* can now be presented for the cost function.

I: i3 85 5 1 8 1 TABLE 2: Example of showing a cost function.

(Q1rb1, P1); (0.1.¾1) 5 4¾1 Δ ^ Δ¾3 ^ ¾1 Zxll Z * 12 .....

^ ¾2 Zx21 Zx22 .....

10 ^ ¾3 ...............

Based on the cost function generation principles 15 described above, all values of Z are non-negative; let Z * be used for the smallest value of Z found and the corresponding changes in edge currents are denoted by ΔΟ ^ 1 = and Δ ^ - Δ ^ · The changes Δ0. * and Δ¾ * required for edge currents have now been found, after which 20 curves and fiber orientation measured profiles and the differences between the target profile are minimized in an optimal way.

Since in the general case the volume flow «0 of the driving point differs from the corresponding Qj of the response point, the values Δ0. * And Δ¾ * retrieved for point 25 must be converted to . to guarantee a point (00, ^ 0 ^ 0 ^. ^, ¾ ^). This is done on the basis of linear weaving theory, ie when the volume flow Q of the lip jet is changed by 6Q: 30 Q - »(1 + 6) 0, (19) the edge flows also change in the same proportion, ie 0. -> (l +«) Qa (20) '• ".35 and ¾“ »(1 + 5) ¾ · (21)

By differentiating formulas (20) and (21), it can be stated that the same i4 8551 8 1 is also valid for changes in edge flow rates: AQa - »(l + δ) AQa (22) and 5 AQjj -» (1 + 6). (23)

Because of the change

Qx - * (1 + 6) Qj = Q0 (24) 10 The quantity δ is δ = (Qq / Qj) - 1, (25) 15 so based on formulas (17) ... (23) at the driving point (Qo'bo ' acid Qa °, Q »0), the differences between the measured curvature and the fiber orientation profile and a target profile is minimized in an optimum manner, the a- and b-side edge of the currents is changed amount: 20 AQaopt = (qq / Q i) · AQA * (26) and AQjj0 * * = (Qq / Q!) · AQj, * · (27) 25 Above AQa * and AQj, * were determined from the discrete set of points Δ0.1, AQa2, AQa3 ··· and AQjj1 # AQj, 2, ΔΟ ^ ... · But if desired, the cost function Z can also be estimated by mathematical interpolation in the intermediate ranges of these, and thus a new, refined minimum and corresponding values of the edge flow changes AQa * and ÄQb * can possibly be found for the cost function.

As it was assumed at this stage that only one response point is available for the control system, in this case we skip the next step and continue * "35 from step 8.

is 8551 8 1 Step 7 In this step, it is assumed that two or more clothing points are available VP ^ = 'w2 = (Qj / bj, Pj / Qa t Qjj) i · · · 5 The first step is to find the driving point AP = (Qq, bg , Ρ ^ Ο ^, Ο ^ ®) are the two closest response points. The distance between the driving point and the response point is defined by formula (18). Let's use this to find the two smallest distances. Without limiting the generality, it is assumed below that VP1 is the nearest and VP2 is the second closest response point to the 10 driving points AP (if necessary, the indexing of the response points can be changed). If Qj = Q2, the changes in the edge flows are retrieved on the basis of the response point VPj alone according to step 6.

15 Next, as described in step 6 above, find the minima of the cost function Z at the response point VPj and VP2. · Enter the values of the edge flow changes corresponding to the minimum of VP ^ Z: AQal * and and at point VPj, respectively: AQa2 and AQjjj * · It is now known that when the volume of the lip jet 20 Q is amended as follows:

Qib ^ Pj) - ♦ (l + 6) -Q (b1> P1) = Q (b2, P2) (28) so that the increases or decreases in edge flows required for optimal adjustment of the curvature and orientation then change by: AQai * - * ( l + fia) · AQal * * AQa2 * (29) and 30 AQ ^ * - (1 + ¾) · AQjjj * - AQbj *. (30)

By keeping the changes 6, 6 ^ and 6 ^ between the points VP1 and VP2 in formulas (28) ... (30) linear, the change is obtained: '•• / 35

QltVPj) - * Q (b0, P0) = (1 + χ · δ) • Q (b1, P1) (31) to correspond to: 16 855 1 8 1 AQal * - * AQa ° pt = (l + x 6a) · ^ Qal * (32) and AQj,! * - * AQjj ° pt = (l + x «b) · ΔΟ ^ *. (33) 5 Since formula (28) gives: δ = (Q ^ Qj) - 1 / (34) is in formula (31): 10 x = (Qo-QjJ / iQj-Qi) / (35) where the abbreviation is used Qq = Q (bQ, Pn). Njrt from formulas (29) and (35) gives: 15 x «a = ((Δ0β2 * / Δ0β1 *) - 1) (Q0-Q1) / (Q2-Q1) (36) and from formulas (30) and (35) respectively ) follows: 20 x 6b = ((AQb / teQbjVl) (Qq-Q!) / (Q2 ~ Qi) · (37>

From formulas (32), (33), (36) and (37) it can now be seen that at the driving point (Qo'bO'P0, ®a ° '®b ° ^ the differences between the measured profile and the target profile of the curvature and the fiber orientation are minimized simultaneously by the optimal in such a way that the edge currents are changed by: - Λ] Δ0> 1 *, *>

30 Q2 “Q1 'AQal I

and

Ar, opt _,. Q0 "Q1 (* ° b2 \] *: ** 35 ^ 1 Γ ~ Γ * ~ 1 ÄQbl <39>

: V35 L VQl I

li i7 8 5 5 1 8 1 Step 8 In steps 6 and 7 above, the quantities ΔQa ° pt and ÄQj, 01 * (ie formulas (26) and (27) and (38) and (39)) were calculated. - and b-side edge of the flows is changed in order to obtain the measured curvature and fiber orientation profiles 5 close to the optimum target profiles. The quantities Δ0 and ^ ° Pt can also be zero if no adjustment is required at all (step 5). Given that the starting situation, that is ajopieteeesä a- and b-side edge flows are Qa® and Qa ^, a new a-and b-side edge flows asetusar-10 butter (= target value) β '' - Q ° * ΔQe. ° pt (40) and

QfetaV - Ob0 ♦ Δ0> ° «*. , 41) 15

Step 9 In this step, the microcomputer 6 (Fig. 1) knows the values (target values) that the edge flows should have, i.e. the values calculated by formulas (40) and (41). Similarly, the computer 20 receives information from the flow meters 2a and 2b, which is the actual flow at any given time. Using this information, the microcomputer 6 adjusts the valves 3a and 3b via the analog signals Qa ° u * and Q ^ ° ut so that the measured values of the edge flows remain at their target values at all times: "25 O.1 * - 0. *" (42) and «b1" - Ob ** '· («) 30 The control program remains at this stage until the user wants to run a new control run or the program run is stopped.

If a new control run is run, the algorithm returns to step 2.

*. ”35 Models of profiles obtained from different stages of the response run are drawn in Figure 4. Figures 4A and 4B show the curvature and fiber orientation profiles in state 1 and Figures 4C and 4D show the corresponding in state 2, i.e. after the edge flows Qa and the change. The results obtained from laboratory measurements ie 8551 8 1 are described in dots and are combined with a dash for clarity. The horizontal axis of the figures depicts the distance in the transverse direction of the paper web (cm), the profiles (vertical axes) are shown in arbitrary units. The differences between the profiles 5 of the states 1 and 2, i.e. the change profiles AK (y) and AQ (y) according to formulas (3) and (4), are drawn in Figures 4E and 4F. Figure 5 illustrates the adjustment run itself: Figures 5A and 5B show an example of an adjustable

the profile of curvature and fiber orientation (points connected by dashed lines). The figures also show the target profiles (solid line) 10 and the upper and lower limits (dashed lines) for the range within which the profiles are desired. In this example, the target profiles and the upper and lower limits are constant over the entire width of the paper web. Figures 5C

and the 5D profiles illustrate the change profiles corresponding to the edge flow changes of the minimum point Z of the cost function, and Figures 5E and 5F show the expected final state obtained by the method of the invention when the profiles of Figures 5A and 5C and the profiles of Figures 5B and 5D are calculated. together; the target profiles and range limits are as in Figures 5A and 5B.

20 It is advisable to repeat the response runs described in step 1 at regular intervals and at least when there are significant changes in the pulp used or the running values of the paper machine, or when the paper produced differs significantly in quality from the quality for which the response runs were performed.

• 25

In particular, it should be noted that the method according to the invention can also be applied to paper machines in which the edge flows can be controlled in some other way, e.g. by removing a small part of the pulp flow through each side wall of the headbox lip channel before discharging to the wire. Likewise, the optimal edge feed rates can be determined by more than two response points. Otherwise, it should be noted that the method according to the invention has been described above with reference to only one embodiment. However, it is in no way intended to limit the invention to this example only, but many modifications are possible within the scope of the inventive idea defined by the following claims.

Claims (7)

1. A method for controlling paper curling profile and fiber orientation profile on a paper machine equipped with edge flow channels, wherein a method is used to control the edge flow rates of the paper machine due to previously collected scoop run data, p because of setting values which rides in the paper machine during the control time by means of the control system that performs the method, characterized in that the curling and fiber orientation profiles are controlled by controlling the side flow quantities in a manner which comprises the following stages: (a) with different setting values of the adjustable paper machine collects data on the relationship between the edge flow changes AQa ^ and ^ ΔΟ ^ resulting from the changes ΔΚ ^ and Δθ ^ in the curl and fiber orientation profile by performing response runs on paper machine (b) relational data obtained at the above defined stage (a) is recorded in the memory of a computer or equivalent belonging to the papermaking control system, and (c) corrected by means of the collected relational data the control system curl profile and the fiber orientation profile of the web to be produced by controlling the eo flow rates of the paper machine. 30 Method according to claim 1, characterized in that said response runs of the paper machine comprise the following stages to be performed on the base of a program (Figures 3A and 3B) registered in the memory of the computer belonging to the control system: (a) to said computer enter data related to the response run, the paper machine and the web to be produced. (B) during the time when the paper machine is in a starting state (downtime 1), a test path is run, hence measured in a laboratory curl profile K ^ fy) and the fiber orientation profile ΘΘ (γ) as well as measured in memory of (c) changing the edge machine of the papermaker in the desired manner and allowing the papermaker to stabilize in the new standstill (final or standstill 2), (d) running with the papermaking test path for the standstill 2, as measured in the laboratory curl profile Κ2 (γ) and the fiber orientation profile Θ2 (γ), measure the measurement results for the computer, and (e) count the change profiles (formulas (3) and (4)), register them in the database of the computer and finish the response run. 1 Patent claim Method according to claim 2, characterized in that the control stage of a program (Figures 3A and 3C) registered in the control system computer comprises the following sub-stages: (a) to the computer the flow profiles for the curling and fiber orientation and the other parameters needed are given. (c) the program of the computer searches in the database of the response run results one or more light response responses and, because of this, determines the new values for flow rates of the edge feeds. (D) adjusting edge flow valves or the equivalent in such a way that the edge flow quantities pour the values calculated at the above defined stage (c), and execution of the regulation maintains the above mentioned point (d), until the control stage ends or a new control run is run by following steps (a), (b), (c) and h (d). 5 4. A method according to any of claims 1-3, characterized in that (a) the response runs are performed by changing the side currents at one or more setting values for the pair of pressure in the paper machine's inlet carriage, the average lip opening, (b) in the control algorithm a cost function is used. (formula (11)) which can be observed by minimizing in the desired manner at the same time both the curl and fiber orientation and the cost function can be extended to cover the curvature and fiber orientation profiles of the entire paper web, (c) the cost function (formula (11)) ) are formed by summing the change profiles obtained from the response runs with the adjustable profiles (formulas (5) and (6)) and, if necessary, bringing the comparable terms associated with the curl and the fiber orientation (formulas ( 7) - (10)), 25 (d) Optimum flow rates for the edge feeds are invented by first determining by minimizing the cost function the change need for the edge feeds at one or more response points (by the answer point is meant the setting values of the papermaker 30 used during the response run), (e) the change needs that have been calculated for the edge feeds in the answer point are calculated setting values which are riding during control time 35 (formulas (26) and (27) when using a response point and formulas (38) and (39) when using two response points), and the curl and fiber orientation profiles are corrected by changing the edge currents according to the values calculated at the above stage (e). 5. Method according to any of claims 1-4, characterized in that in the process the cantile flow rates are controlled by the paper machine by means of control valves (3a) and (3b) or the corresponding and a control system which atures them (Figure 1). 10 Method according to any of claims 1-5, characterized in that the computer of the control system, which is most preferably a microcomputer (6), counts on account of this fed adjustable profiles and counting parameters and the database of the response runs recorded in the memory of the computer. necessary optimal quantities of the edge feeds, which in a connection unit (7) are converted into control quantities, which control the control valves (3a) and (3b), or the like (Figure 1). Method according to any one of claims 1-6, characterized in that the quantities of the edge currents are measured every moment by the flow meters (2a) and (2b) and these measurement quantities are converted in the connection unit (7) to one for the computer (6). light-like shape, after which the program of the computer compares measured values with the measured values calculated by the control algorithm and changes, if necessary, control quantities, which should be set to control valves (3a) and (3b), or the equivalent, so that the measured values for the edge currents should be the same as the calculated mean values are as accurate as possible (Figure 1). 30 II