CONTINUOUS ROLLING SYSTEM

Abstract

When the tracking point reaches the i-th stand, the continuous rolling system outputs, to an i-th stand, a roll gap operation value for bringing to zero a difference between a value which is obtained by correcting a strip thickness target value of the i-th stand with a target strip thickness correction value of the i-th stand and a value which is obtained by correcting a strip thickness actual recalculation value of the i-th stand with a gap correction value of the i-th stand. Here, the gap correction value is a correction value that brings to zero a difference between a head end gap error when a head end of the material to be rolled reaches the i-th stand and a non-head end gap error when a part other than the head end of the material to be rolled reaches the i-th stand.

Claims

1. A continuous rolling system that changes product specifications during continuous rolling of one strip of a material to be rolled, comprising: a tandem rolling mill including a plurality of rolling stands, each of the plurality of rolling stands controlling a roll gap according to a roll gap operation value; a strip thickness gauge provided on a delivery side of the tandem rolling mill, the strip thickness gage measuring strip thickness of the material to be rolled; and a roll force distribution control device matching an actual roll force ratio between the plurality of rolling stands with a target roll force ratio; wherein the roll force distribution control device comprising: a setting calculation unit determining: a strip thickness target value of each of the plurality of rolling stands; and a roll force distribution ratio target value of each of the plurality of rolling stands, the roll force distribution ratio target value representing the target roll force ratio between the plurality of rolling stands; an actual data collection unit collecting: a roll force actual value of each of the plurality of rolling stands; a roll gap actual value of each of the plurality of stands, the roll gap actual value being calculated based on the roll gap operation value of each of the plurality of rolling stands; a roll rotational speed actual value of each of the plurality of rolling stands; and a strip thickness measurement value obtained by measurement with the strip thickness gauge; a mass flow thickness correction unit performing: calculating a strip thickness actual value of each of the plurality of rolling stands based on the strip thickness measurement value and the roll rotational speed actual value of each of the plurality of rolling stands; calculating a strip thickness actual recalculation value of each of the plurality of rolling stands based on the roll force actual value of each of the plurality of rolling stands and the roll gap actual value of each of the plurality of rolling stands; calculating a gap error of each of the plurality of rolling stands based on a difference between the strip thickness actual value of each of the plurality of rolling stands and the strip thickness actual recalculation value of each of the plurality of rolling stands; and calculating a gap correction value of each of the plurality of rolling stands, the gap correction value being for preventing the gap error of each of the plurality of rolling stands from being changed; a target strip thickness correction value calculation unit performing: calculating a roll force distribution ratio actual value of each of the plurality of rolling stands, the roll force distribution ratio actual value representing the actual roll force ratio between the plurality of rolling stands, based on the roll force actual value of each of the plurality of rolling stands; and calculating a target strip thickness correction value of each of the plurality of stands based on a difference between the roll force distribution ratio target value of each of the plurality of rolling stands and the roll force distribution ratio actual value of each of the plurality of rolling stands; a tracking unit tracking a tracking point, the tracking point being set on the material to be rolled; and a gap operation unit outputting, when the tracking point reaches each of the plurality of rolling stands, the roll gap operation value to a target rolling stand, the target rolling stand being the each rolling stand reached by the tracking point, the roll gap operation value bringing, to zero, a difference between a value obtained by correcting the strip thickness target value of the target rolling stand with the target strip thickness correction value of the target rolling stand and a value obtained by correcting the strip thickness actual recalculation value of the target rolling stand with the gap correction value of the target rolling stand.

2. The continuous rolling system according to claim 1 wherein the gap correction value is a correction value bringing to zero a difference between a correction reference gap error and a non-head-end gap error, the correction reference gap error being the gap error when a head end of the material to be rolled reaches the rolling stand, the non-head-end gap error being the gap error when a part other than the head end of the material to be rolled reaches the rolling stand.

3. The continuous rolling system according to claim 1, comprising: a gap operation end intervention unit allowing the roll gap operation value to be changed based on an intervention signal by an operator; wherein the roll force distribution control device performs: calculating the roll force distribution ratio actual value of each of the plurality of rolling stands based on the roll force actual value of each of the plurality of rolling stands, the roll force actual value being collected after the roll gap operation value having been changed is applied to the tandem rolling mill; and updating the roll force distribution ratio target value of each of the plurality of rolling stands with the roll force distribution ratio actual value of each of the plurality of rolling stands.

4. The continuous rolling system according to claim 2, wherein the roll force distribution control device performs: interrupting calculation of the gap correction value and the target strip thickness correction value before executing flying strip thickness change, the flying strip thickness change causing the strip thickness target value of the tandem rolling mill to be changed without stopping rolling by the tandem rolling mill; storing the correction reference gap error before execution of the flying strip thickness change; resetting the roll force distribution ratio target value for the flying strip thickness change; calculating the correction reference gap error after the execution of the flying strip thickness change, by adding a difference to the correction reference gap error before the execution of the flying strip thickness change, the difference being between the gap error after the execution of the flying strip thickness change and the gap error before the execution of the flying strip thickness change; and resuming the calculation of the gap correction value and the target strip thickness correction value after calculating the correction reference gap error after the execution of the flying strip thickness change.

5. The continuous rolling system according to claim 1, wherein the roll force distribution control device performs: storing a table defining a relationship between a type and size of the material to be rolled and a control gain and; obtaining, from the table, the control gain corresponding to the type and size of the material to be rolled; and the gap correction value is calculated by multiplication by the control gain; and the target strip thickness correction value is calculated by multiplication by the control gain.

6. The continuous rolling system according to claim 1, wherein the rolling stand includes an actuator controlling a shape of the material to be rolled; and the roll force distribution control device performs change of the roll force distribution ratio target value of the rolling stand having the actuator, the change being performed in a direction of reducing an output of the actuator when the output reaches an upper limit value and in a direction of increasing an output of the actuator when the output reaches a lower limit value.

7. The continuous rolling system according to claim 4, wherein the roll force distribution control device reduces the gap error gradually with time, the gap error occurring during changing of strip thickness by the flying strip thickness change.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0083] FIG. 1 is a diagram for describing a system configuration of a continuous rolling system according to a first embodiment.

[0084] FIG. 2 is a diagram that shows a part of a hot rolling line where metal is processed.

[0085] FIG. 3 is a diagram for describing a configuration of a rolling stand.

[0086] FIG. 4 is a graph that shows changes in a roll force actual value and gap actual value due to a temperature change on a rolling line entry side.

[0087] FIG. 5 is graphs that show a change in roll force of each stand due to temperature change on the rolling line entry side.

[0088] FIG. 6 is a diagram that shows a change in a roll diameter for which the amount of thermal expansion and the amount of abrasion are taken into consideration.

[0089] FIG. 7 is a graph that shows changes in the gap actual value and roll force actual value when the amount of abrasion increases.

[0090] FIG. 8 is a diagram that shows control timings of the continuous rolling system according to the first embodiment.

[0091] FIG. 9 is a diagram for describing an output timing of a correction value according to a position of a tracking point.

[0092] FIG. 10 is a diagram that shows a control result over a total length of a material to be rolled on an upstream side stand.

[0093] FIG. 11 is a diagram that shows examples of roll force actual values at the start time of rolling and before the end of rolling.

[0094] FIG. 12 is a diagram for describing a system configuration of a continuous rolling system according to a second embodiment.

[0095] FIG. 13 is a diagram for describing roll force distribution control after gap intervention in the second embodiment.

[0096] FIG. 14 is a diagram for describing an example of modifying a roll force distribution ratio target value at the time of the gap intervention in the second embodiment.

[0097] FIG. 15 is a diagram that shows control timings of a continuous rolling system according to a third embodiment.

[0098] FIG. 16 is a diagram that shows a setting example of a table according to a fourth embodiment.

[0099] FIG. 17 is a conceptual diagram that shows a hardware configuration example of a processing circuit included in a roll force distribution control device 10 in each of the embodiments.

DESCRIPTION OF EMBODIMENTS

[0100] Hereinafter, embodiments of the present disclosure will be described in detail with reference to drawings. However, when numbers such as the number, quantity, volume, or range of elements are referred to in the embodiments presented below, the present disclosure is not limited by the numbers referred to except where especially explicitly specified and where clearly specified to the numbers in principle. In addition, structures and the like that are described in the embodiments presented below are not necessarily required for this disclosure except where especially explicitly specified and where clearly specified thereto in principle. Note that common elements in the drawings are denoted by the same reference signs to omit redundant explanations.

[0101] As described above, herein, the “rolling stand” is also simply described as “stand.” The “roll gap” is also simply described as “gap.” The “delivery side strip thickness” is also simply described as “strip thickness.” Therefore, the “strip thickness target value,” “strip thickness actual value,” and “strip thickness actual recalculation value” relate to a strip thickness on a stand delivery side.

First Embodiment

[0102] (System Configuration)

[0103] A first embodiment of the present disclosure will be described. FIG. 1 is a diagram for describing a system configuration of a continuous rolling system according to the first embodiment of the present disclosure. The continuous rolling system that changes product specifications during continuous rolling of one material to be rolled includes a roll force distribution control device 10 and a rolling line 20. The rolling line 20 is a hot rolling line. As shown in FIG. 2, the rolling line 20 includes a tandem rolling mill 2 having a plurality of rolling stands. Each of the plurality of rolling stands controls a roll gap according to a roll gap operation value. A concrete configuration example of the rolling line 20 is the same as in FIG. 2 and FIG. 3 described above and therefore, the explanation thereof will be omitted.

[0104] The roll force distribution control device 10 includes, in order to match an actual roll force ratio between the plurality of rolling stands with a target roll force ratio, an operating instruction input unit 1b, a setting calculation unit 1c, a gap operation unit 1d, an actual data collection unit 1e, a target strip thickness operation unit 1f, a roll force distribution modification unit 1g, a target strip thickness correction value calculation unit 1h, a mass flow thickness correction unit 1i, and a tracking unit 1j.

[0105] The operating instruction input unit 1b outputs, to the setting calculation unit 1c, an operating instruction that includes base material information of a material to be rolled 2b (entry side strip thickness, entry side strip width, type, etc.) and target information of the material to be rolled 2b (strip thickness, strip width, temperature, etc.).

[0106] The setting calculation unit 1c determines, based on the base material information and the target information, at least a strip thickness target value of each stand, a gap setting value of each stand, and a roll circumferential speed setting value of each stand.

[0107] In addition, the setting calculation unit 1c calculates two parameters (entry side strip thickness influence coefficient Q.sub.i and roll force distribution ratio target value γ.sub.i.sup.AIM) described later, and outputs to the roll force distribution modification unit 1g.

[0108] Furthermore, the setting calculation unit 1c determines the use or non-use of roll force distribution control by the roll force distribution modification unit 1g.

[0109] The actual data collection unit 1e continuously collects from the rolling line 20: a roll force actual value of each stand; a gap actual value of each stand; a roll rotational speed actual value of each stand; and a strip thickness measurement value on a final stand (the N-th stand) delivery side.

[0110] Here, the roll force actual value is a calculation value that is calculated from either a measurement value obtained by measurement with each of load cells 3d or a measurement value obtained by measurement with a pressure gauge that measures pressure of each of hydraulic cylinders 3c.

[0111] The gap actual value is the size of a roll gap that is calculated from an amount by which the hydraulic cylinder 3c as an actuator controlling the roll gap is operated. The amount by which the hydraulic cylinder 3c is operated is based on a roll gap operation value. Thus, the gap actual value does not include a change in a roll diameter due to the amount of abrasion and amount of thermal expansion described above. Therefore, there is a deviation between the gap actual value and a gap true value that is the size of a real roll gap for which a change in a roll diameter due to the amount of abrasion and amount of thermal expansion of rolls is taken into consideration.

[0112] The roll rotational speed actual value is a work roll rotational speed which is measured by encoders 3e. A roll circumferential speed actual value is calculated from the roll rotational speed actual value.

[0113] The strip thickness measurement value is a measurement value obtained by measurement with a strip thickness gauge 2c that is provided on a delivery side of the tandem rolling mill 2.

[0114] The target strip thickness operation unit 1f changes, when there is a difference between the strip thickness measurement value and a strip thickness target value of a final stand during rolling, a strip thickness target value of each stand other than the final stand, which is set by the setting calculation unit 1c, so as to bring the difference to zero.

[0115] In addition, the target strip thickness operation unit 1f receives, when a tracking point which is set on the material to be rolled 2b reaches the i-th stand (1≤i≤N), an input of a target strip thickness correction value of the i-th stand from the roll force distribution modification unit 1g during the execution of the roll force distribution control described later. Then, the target strip thickness operation unit 1f corrects the strip thickness target value of the i-th stand with the target strip thickness correction value of the i-th stand. The corrected strip thickness target value is output to the gap operation unit 1d.

[0116] The roll force distribution modification unit 1g includes: a target strip thickness correction value calculation unit 1h, a mass flow thickness correction unit 1i, and a tracking unit 1j, for executing the roll force distribution control.

[0117] The roll force distribution modification unit 1g outputs, when a tracking point which is set on the material to be rolled 2b reaches the i-th stand, a gap correction value of the i-th stand to the gap operation unit 1d and a target strip thickness correction value of the i-th stand to the target strip thickness operation unit 1f during the execution of the roll force distribution control.

[0118] The target strip thickness correction value calculation unit 1h receives an input of a roll force distribution ratio target value of each stand which is set by the setting calculation unit 1c and a roll force actual value of each stand which is collected by the actual data collection unit 1e.

[0119] The target strip thickness correction value calculation unit 1h calculates a roll force distribution ratio actual value of each stand, which represents an actual roll force ratio between stands, based on the roll force actual value of each stand.

[0120] The target strip thickness correction value calculation unit 1h calculates a target strip thickness correction value of each stand, based on a difference between the roll force distribution ratio target value of each stand and a roll force distribution ratio actual value of each stand.

[0121] The mass flow thickness correction unit 1i calculates a strip thickness actual value of each stand, based on the strip thickness measurement value and the roll rotational speed actual value of each stand.

[0122] The mass flow thickness correction unit 1i calculates a strip thickness actual recalculation value of each stand, based on the roll force actual value of each stand and a gap actual value of each stand.

[0123] The mass flow thickness correction unit 1i calculates a gap error of each stand, based on a difference between the strip thickness actual value of each stand and the strip thickness actual recalculation value of each stand.

[0124] The mass flow thickness correction unit 1i calculates a gap correction value for each stand for preventing a gap error of each stand from varying. Here, the gap correction value is a correction value that brings to zero a difference between a head end gap error (correction reference gap error) when a head end of the material to be rolled 2b reaches the i-th stand (19≤i≤N) and a non-head-end gap error when a part other than the tip end of the material to be rolled 2b reaches the i-th stand.

[0125] The tracking unit 1j tracks a tracking point which is set on the material to be rolled 2b, based on the roll rotational speed actual value.

[0126] The gap operation unit 1d outputs, before start of rolling, an actuator control signal (roll gap operation value, roll rotational speed value) to the rolling line 20 so as to match the roll gap and roll circumferential speed of each stand with the setting values thereof. An actuator that controls the roll gap is each of the hydraulic cylinders 3c. An actuator that controls the roll circumferential speed is a drive device for work rolls.

[0127] The gap operation unit 1d outputs, during rolling, a roll gap operation value for bringing to zero a difference between the strip thickness target value of each stand and the strip thickness actual recalculation value of each stand, to the rolling line 20 (hydraulic cylinders 3c).

[0128] In addition, the gap operation unit 1d receives, when a tracking point reaches the i-th stand (target rolling stand), an input of a gap correction value of the i-th stand from the roll force distribution modification unit 1g during the execution of the roll force distribution control. At the same time, the gap operation unit 1d receives an input of the strip thickness target value of the i-th stand which has been corrected by the target strip thickness operation unit 1f.

[0129] Then, the gap operation unit 1d outputs, to the i-th stand, a roll gap operation value for bringing to zero a difference between the strip thickness target value of the i-th stand which has been corrected by the target strip thickness operation unit 1f and a value which has been obtained by correcting the strip thickness actual recalculation value of the i-th stand with the gap correction value of the i-th stand. The hydraulic cylinders 3c of the i-th stand change a roll gap based on the roll gap operation value.

[0130] Next, the operation of the continuous rolling system will be described with reference to FIG. 8 to FIG. 11. FIG. 8 is a diagram that shows control timings of the continuous rolling system. Details of the control timings and the control thereof will be described based on FIG. 1 and FIG. 8.

[0131] (Control Timing 8a: Setting Calculation)

[0132] The 8a is a timing before a material to be rolled reaches the most upstream stand (the first stand). At the control timing 8a, setting calculation is executed.

[0133] The setting calculation unit 1c receives an input of the base material information of the material to be rolled and the target information of the material to be rolled which are described above, from the operating instruction input unit 1b. The setting calculation unit 1c determines at least a gap setting value of each stand and a roll circumferential speed setting value of each stand, based on the base material information of the material to be rolled and the target information of the material to be rolled.

[0134] The gap operation unit 1d outputs an actuator control signal (roll gap operation value, roll rotational speed value) to the rolling line 20 so as to match the roll gap and roll circumferential speed of each stand with the setting values thereof.

[0135] The setting calculation unit 1c calculates two parameters which are required by the roll force distribution modification unit 1g. The two parameters are an entry side strip thickness influence coefficient Q.sub.i and a roll force distribution ratio target value γ.sub.i.sup.AIM.

[0136] The entry side strip thickness influence coefficient Q.sub.i is a value indicating the amount of change in roll force with respect to a change in a strip thickness and is represented by equation (9).

[00001]$\begin{array}{cc}\left[\mathrm{Math}.9\right]& \\ Q_i={\left(\frac{\partial P\left(T,H,h,V,.Math.\right)}{\partial h}\right)}^{\mathrm{CAL}}& \left(9\right)\end{array}$

[0137] where [0138] Q.sub.i: an entry side strip thickness influence coefficient of the i-th stand

[0139] The roll force distribution ratio target value γ.sub.i.sup.AIM represents a target ratio of roll force of each stand. The roll force distribution ratio target value γ.sub.i.sup.AIMN is determined, for example, by using roll force which is predicted when the setting calculation unit 1c determines a roll gap, as in equation (10).

[Math. 10]

γ.sub.1.sup.AIM:γ.sub.2.sup.AIM:γ.sub.3.sup.AIM: . . . :γ.sub.i.sup.AIM: . . . :γ.sub.N.sup.AIM:=P.sub.1.sup.Pre:P.sub.2.sup.Pre:P.sub.3.sup.Pre: . . . :P.sub.i.sup.Pre: . . . :P.sub.N.sup.Pre:   (10)

[0140] where [0141] P.sub.i.sup.Pre: a roll force prediction value of the i-th stand [kN] [0142] γ.sub.i.sup.AIM: a roll force distribution ratio target value of the i-th stand [-]

[0143] The entry side strip thickness influence coefficient Q.sub.i and the roll force distribution ratio target value γ.sub.i.sup.AIM are used in calculation of a target strip thickness correction value Δh.sup.BAL(i) by the roll force distribution modification unit 1g (target strip thickness correction value calculation unit 1h) described later.

[0144] After the control timing 8a, the material to be rolled 2b is conveyed from the upstream side of the rolling line 20 and rolling starts.

[0145] The actual data collection unit 1e continues collecting measurement data including a roll force actual value of each stand; a roll rotational speed actual value of each stand, a strip thickness measurement value on a final stand delivery side, from the start of rolling to the end of rolling.

[0146] The target strip thickness operation unit 1f changes during rolling, when there is a difference between the strip thickness measurement value and the strip thickness target value of a final stand, the strip thickness target value of each stand (the first stand to the N−1-th stand) so as to bring the difference to zero. The corrected strip thickness target value is output to the gap operation unit 1d.

[0147] The gap operation unit 1d outputs, during rolling, a roll gap operation value for bringing to zero a difference between the strip thickness target value of each stand and the strip thickness actual recalculation value of each stand, to the rolling line 20 (hydraulic cylinders 3c). Each of the hydraulic cylinders 3c change a roll gap, based on the roll gap operation value.

[0148] (Control Timing 8b: Calculation of Correction Reference Gap Error)

[0149] The 8b is a timing at which after passing sequentially from the most upstream stand to the final stand, the head end of the material to be rolled 2b further reaches the strip thickness gauge 2c.

[0150] At the control timing 8b, the mass flow thickness correction unit 1i calculates a correction reference gap error of each stand. The correction reference gap error is a gap error (head end gap error) when the head end of the material to be rolled 2b reaches the i-th stand (1≤i≤N).

[0151] More specifically, the mass flow thickness correction unit 1i calculates a correction reference gap error S.sup.OFS(i) of each stand, based on a difference between a strip thickness actual value when the head end of the material to be rolled 2b passes through the i-th stand and the strip thickness actual recalculation value of the i-th stand.

[0152] The strip thickness actual recalculation value h.sup.GM(i) is calculated as in equation

[Math. 11]

h.sup.GM(i)=S.sub.i.sup.act+P.sub.i.sup.act/M.sub.iα.sub.i   (11)

[0153] where [0154] S.sub.i.sup.act: a gap actual value of the i-th stand [mm] [0155] P.sub.i.sup.act: a roll force actual value of the i-th stand [kN] [0156] α.sub.i: an offset value of the i-th stand (for example, a gap learning value) [mm]

[0157] When a strip thickness gauge is placed on a stand delivery side, the strip thickness actual value h.sup.MF(i) is a measurement value of the strip thickness gauge. When a strip thickness gauge is not placed on a stand delivery side, the strip thickness actual value h.sup.MF(i) is calculated from a roll circumferential speed actual value, a strip thickness measurement value on the final stand delivery side, and a forward slip ratio, as shown in equation (12).

[Math. 12]

h.sup.MF(i)=h.sup.MES(N).Math.(1+fs.sup.ACAL(N).Math.V.sup.ACT(N)/(1fs.sup.ACAL(i)/V.sup.ACT(i)   (12)

[0158] where [0159] V.sup.ACT(i): a roll circumferential speed actual value of the i-th stand [mm] [0160] h.sup.MES(N): a strip thickness measurement value on the N-th stand (final stand) delivery side [mm] [0161] fs.sup.ACAL(i): a forward slip ratio of the i-th stand [-]

[0162] where, the roll circumferential speed actual value is the one collected at the same time for all stands. The strip thickness measurement value is a measurement value of the strip thickness gauge 2c that is placed on the final stand delivery side. The forward slip ratio fs.sup.ACAL(i) is a ratio between a roll circumferential speed and a roll delivery side material-to-be-rolled speed; and changes according to at least a draft which is represented by a ratio between the amount of strip thickness change and entry side strip thickness of a stand.

[Math. 13]

fs.sup.ACAL(i_=fs((h.sup.MF(i−1)−h.sup.MF(i)/h.sup.MF(i−1), . . . )   (13)

[0163] When a strip thickness actual value changes, a forward slip ratio changes, and when the forward slip ratio changes, the strip thickness actual value changes; and therefore, the strip thickness actual value described above can be obtained by performing convergent calculation.

[0164] As described above, the strip thickness actual recalculation value can be calculated from equation (11). The strip thickness actual value can be obtained by a convergent calculation between equation (12) and equation (13). Therefore, the correction reference gap error S.sup.OFS(i) is calculated as in equation (14).

[Math. 14]

S.sup.OFS()=h.sup.GM_hd(i)−h.sup.MF_hd(i)   (14)

[0165] The h.sup.GM_hd(i) in equation (14) is represented by equation (15).

[Math. 15]

h.sup.GM_hd(i)=S.sub.i.sup.adct_hd+P.sub.i.sup.act_hd/M.sub.i+α.sub.i   (15)

[0166] where [0167] h.sup.GM_hd(i): a strip thickness actual recalculation value at the head end of a material to be rolled on the i-th stand [mm] [0168] S.sub.i.sup.act_hd: a gap actual value at the head end of the material to be rolled on the i-th stand [mm] [0169] P.sub.i.sup.act_hd : a roll force actual value at the head end of the material to be rolled on the i-th stand [mm] [0170] α.sub.i: an offset value of the i-th stand (for example, a gap learning value) [mm]

[0171] The h.sup.MF_hd(i) in equation (14) is represented by equation (16).

[Math. 16]

h.sup.MF_hd(i)=h.sup.MES_hd(N).Math.(1+fs.sup.ACAL_hd(N)).Math.V.sup.ACT_hd(N)/(1+fs.sup.ACL_hd(i))/V.sup.ACT_hd(i)   (16)

[0172] The fs.sup.ACAL_hd(i) in equation (16) is represented by equation (17).

[Math. 17]

fs.sup.ACAL_hd(i)=fs((h.sup.MF_hd(i−1)−h.sup.MF_hd(i))/h.sup.MF_hd(i−1), . . . )   (17)

[0173] where [0174] h.sup.MF_hd(i): a strip thickness actual value at the head end of a material to be rolled on the i-th stand [mm] [0175] V.sup.ACT_hd(i): a roll circumferential speed at the head end of the material to be rolled on the i-th stand (collected at timing 8b) [m/s] [0176] h.sup.MES_hd(N): a strip thickness measurement value at the head end of the material to be rolled on the N-th stand (final stand) delivery side [mm] [0177] fs.sup.ACAL_hd(i): a forward slip ratio of the i-th stand [-]

[0178] (Control Timing 8c: Calculation of A Gap Correction Value and a Target Strip Thickness Correction Value)

[0179] In recent years, coils of thin size have been manufactured. In rolling for a thin size, if an abrupt load change and a speed balance change occur due to an abrupt gap change, rolling becomes unstable due to shape irregularities and a deterioration of tension between stands, where a serious trouble such as strip breakage is more likely to occur. Therefore, it is not preferable to abruptly change a gap immediately after passing of a material to be rolled, immediately after a size change, or the like.

[0180] For these reasons, the roll force distribution control is not performed immediately after the start of strip thickness measurement since rolling at a head end non-steady part is performed then. The roll force distribution modification unit 1g executes the roll force distribution control, for example, after the head end of the material to be rolled 2b has passed LS[m] since reaching the strip thickness gauge 2c. In the roll force distribution control, a gap correction value and a target strip thickness correction value are calculated.

[0181] The 8c is a control timing at which correction value calculation starts. It is no problem whether a calculation timing of a gap correction value by the mass flow thickness correction unit 1i and a calculation timing of a target strip thickness correction value by the target strip thickness correction value calculation unit 1h are simultaneous or either of them precedes the other. Here, an example where the calculations are simultaneously performed is described.

[0182] First, the calculation of a gap correction value will be described. The mass flow thickness correction unit 1i calculates a gap correction value of each stand, based on a difference between the strip thickness actual value of each stand and the strip thickness actual recalculation value of each stand.

[0183] First, the mass flow thickness correction unit 1i calculates a gap error S.sup.EER(i), based on the strip thickness actual recalculation value h.sup.GM(i) which is calculated by using equation (11) and the strip thickness actual value h.sup.MF(i) which is calculated by using equation (12) (equation (18)). The gap error S.sup.EER(i) is a non-head-end gap error when a part other than the head end of the material to be rolled 2b reaches the i-th stand.

[0184] In addition, the mass flow thickness correction unit 1i determines the amount of change in a gap error from the head end by comparing this gap error SEER(i) and the above-described correction reference gap error S.sup.OFS(i) by using the equation (20). The mass flow thickness correction unit 1i calculates a gap correction value for bringing the amount of change in the gap error to zero. The mass flow thickness correction unit 1i applies an adjustment gain as shown in equation (21) and performs a limit check with the maximum value and minimum value of an output as shown in equation (22), thereby determining a final gap correction value ΔS.sup.COMP(i).

[Math. 18]

S.sup.ERR(i)=h.sup.GM(i)−h.sup.MF(i)   (18)

[Math. 19]

S.sup.ERR_PREV(i)=S.sup.ERR(i)   (19)

[Math. 20]

err(i)=S.sup.ERR(i)−S.sup.OFS(i)   (20)

[Math. 21]

ΔS.sup.COMP(i)=G.sup.SCOMP(i).Math.{ΔS.sup.COMP_Prev(i)+β(i).Math.err(i)}  (21)

[Math. 22]

ΔS.sup.COMP(i)=Clamp(ΔS.sup.COMP(i),ΔS.sup.COMP_UL(i)ΔS.sup.COMP_LL(i))   (22)

[0185] where [0186] ΔS.sup.COMP_Prev(i): a previous output value of the i-th stand (initial value is 0) [0187] β(i): an update gain of the i-th stand [-] [0188] G.sup.SCOMP(i): a correction output gain of the i-th stand [-] [0189] ΔS.sup.COMP_UL(i): a gap correction upper limit value of the i-th stand [mm] [0190] ΔS.sup.COMP_LL(i): a gap correction lower limit value of the i-th stand [mm] [0191] S.sup.ERR(i): a gap error of the i-th stand [mm] [0192] ΔS.sup.COMP(i): a gap correction value of the i-th stand [mm]

[0193] The strip thickness actual recalculation value h.sup.GM(i) after correction which is shown by equation (23) is a value obtained by subtracting the above gap correction value ΔS.sup.COMP(i) which has been output, from the strip thickness actual recalculation value h.sup.GM(i) shown by equation (11).

[Math. 23]

h.sup.GM(i)=S.sub.i.sup.act+P.sub.i.sup.act/M.sub.i+α.sub.i−S.sup.COMP(i)   (23)

[0194] Next, the calculation of a target strip thickness correction value will be described. The target strip thickness correction value calculation unit 1h calculates a target strip thickness correction value Δh.sup.BAL(i) by comparing a current roll force actual value P.sub.i.sup.act and a roll force distribution ratio target value γ.sub.i.sup.AIM, so as to bring the roll force distribution ratio actual value close to the roll force distribution ratio target value γ.sub.i.sup.AIM. For example, the target strip thickness correction value Δh.sup.BAL(i) is calculated by using the following equation.

[00002]$\begin{array}{cc}\left[\mathrm{Math}.24\right]& \\ \Delta h_{i-1}^{\mathrm{BAL}0}=-\frac{1}{Q_i}\left(P_i^{\mathrm{ACT}}-A.Math.{\gamma }_i^{\mathrm{AIM}}\right)+\Delta h_i^{\mathrm{BAL}0}& \left(24\right)\end{array}$$\begin{array}{cc}\left[\mathrm{Math}.25\right]& \\ A=\frac{\frac{P_1^{\mathrm{ACT}}}{Q_1}+\frac{P_2^{\mathrm{ACT}}}{Q_2}+.Math.+\frac{P_5^{\mathrm{ACT}}}{Q_5}}{\frac{{\gamma }_1^{\mathrm{AIM}}}{Q_1}+\frac{{\gamma }_2^{\mathrm{AIM}}}{Q_2}+.Math.+\frac{{\gamma }_5^{\mathrm{AIM}}}{Q_5}}& \left(25\right)\end{array}$

[0195] The coefficient A is common to all stands. Q.sub.i and Δ.sub.i.sup.AIM are calculated in advance by using the equation (9) and the equation (10) by the setting calculation unit 1c. where, Δh.sub.i.sup.BAL0 in equation (24) is zero for the final stand F.sub.N as shown in equation (26) and is calculated sequentially from a latter stand.

[00003]$\begin{array}{cc}\left[\mathrm{Math}.26\right]& \\ \Delta h_N^{\mathrm{BAL}0}=0\Delta h_{N-1}^{\mathrm{BAL}0}=-\frac{1}{Q_N}\left(P_N^{\mathrm{ACT}}-A.Math.{\gamma }_N^{\mathrm{AIM}}\right)+\Delta h_N^{\mathrm{BAL}0}.Math.\Delta h_1^{\mathrm{BAL}0}=-\frac{1}{Q_2}\left(P_2^{\mathrm{ACT}}-A.Math.{\gamma }_2^{\mathrm{AIM}}\right)+\Delta h_2^{\mathrm{BAL}0}& \left(26\right)\end{array}$

[0196] The target strip thickness correction value calculation unit 1h applies an adjustment gain as shown in equation (27) and performs a limit check as shown in equation (28), thereby determining a final target strip thickness correction value Δh.sup.BAL(i).

[Math. 27]

dh=G.sup.BAL(i).Math.{Δh.sup.BAL_Prev(i)+β(i).Math.Δh.sup.BAL0(i)}  (27)

[Math. 28]

Δh.sup.BAL(i)=Clamp(dh,Δh.sup.BAL_UL(i),Δh.sup.BAL_LL(i))   (28)

[Math. 29]

Δh.sup.BAL_Prev(i)=Δh.sup.BAL(i)   (29)

[0197] where [0198] Δh.sup.BAL_Prev(i): a previous value of the i-th stand (initial value=0) [mm] [0199] Δh.sup.BAL(i): a target strip thickness correction value of the i-th stand [mm] [0200] β(i): an update gain of the i-th stand (adjustment value, for example, 0.3) (0≤β≤1.0) [0201] G.sup.BAL(i): a correction output gain of the i-th stand (adjustment value, for example, 0.5) (0≤G.sup.BAL(i)≤1.0)

[0202] As described above, during the execution of the roll force distribution control, the mass flow thickness correction unit 1i calculates a gap correction value of each stand and the target strip thickness correction value calculation unit 1h calculates a target strip thickness correction value of each stand.

[0203] (Control Timing 8d: Correction of a Delivery Side Strip Thickness Target Value and Correction of a Strip Thickness Actual Recalculation Value, Using a Tracking Function)

[0204] Next, by using the tracking unit 1j, the above target strip thickness correction value calculated by the target strip thickness correction value calculation unit 1h and the above gap correction value calculated by the mass flow thickness correction unit 1i are output to the target strip thickness operation unit 1f and the gap operation unit 1d, respectively, sequentially from an upstream side stand.

[0205] The 8d is a control timing at which a gap correction value and target strip thickness correction value of the most upstream stand are output during the execution of roll force distribution control. At the control timing 8d, the gap correction value and target strip thickness correction value of the most upstream stand are output.

[0206] Simultaneously, the tracking unit 1j sets a tracking point on the material to be rolled 2b positioned on the most upstream stand. The tracking unit 1j tracks the tracking point, based on the roll rotational speed actual value. The roll force distribution modification unit 1g outputs, when the tracking point reaches a downstream side stand, a gap correction value and target strip thickness correction value of the downstream side stand.

[0207] The target strip thickness operation unit 1f corrects a strip thickness target value of the i-th stand with a target strip thickness correction value of the i-th stand. The corrected strip thickness target value is output to the gap operation unit 1d.

[0208] The gap operation unit 1d outputs, to the i-th stand, a roll gap operation value for bringing to zero a difference between the strip thickness target value of the i-th stand which has been corrected by the target strip thickness operation unit 1f and a value which has been obtained by correcting the strip thickness actual recalculation value of the i-th stand with the gap correction value of the i-th stand (equation (23)). The hydraulic cylinder 3c of the i-th stand changes a roll gap, based on the roll gap operation value.

[0209] FIG. 9 is a diagram for describing an output timing of a correction value according to the position of the tracking point. First, a gap correction value ΔS.sup.COMP(1) and target strip thickness correction value Δh.sup.BAL(1) of the first stand F.sub.1 (the most upstream stand) are output (9a). At this time, a part of the material to be rolled 2b positioned on the first stand F1 is set as a tracking point A (9b). When the tracking point A reaches the second stand F.sub.2, a gap correction value ΔS.sup.COMP(2) and target strip thickness correction value Δh.sup.BAL(2) of the second stand F.sub.2 is output. Subsequently, when the tracking point A reaches the i-th stand on a downstream side, a gap correction value ΔS.sup.COMP(i) and target strip thickness correction value Δh.sup.BAL(i) of the i-th stand are output (9c). The tracking unit 1j performs tracking until the tracking point A reaches the strip thickness gauge 2c on the N-th stand (final stand) delivery side. Note that the processing order of 9a and 9b may be in reverse.

[0210] (Control Timing 8e: Repetition of Control)

[0211] When a roll gap is operated according to calculation of a gap correction value and a target strip thickness correction value by the above-described roll force distribution control, fluctuations occur in a roll force actual value, a tension detection value between stands, and the like. Since these fluctuations are disturbances in control, the roll force distribution modification unit 1g does not recalculate a correction value until the fluctuations subside to a certain degree and after a given period of time has passed, recalculates a correction value.

[0212] The 8e in FIG. 8 is a control timing after a given period of time t_slope has passed since the tracking point has reached the strip thickness gauge 2c. For example, at the control timing 8e, a gap correction value and a target strip thickness correction value are determined again; a tracking point is created at the same time when a correction value of the most upstream stand to be operated is changed; and a correction value is changed sequentially from an upstream side stand. Subsequently, the control is continued until a control end timing comes.

[0213] (Control Timing 8f: End of Control)

[0214] The 8f in FIG. 8 is a control timing at which the roll force distribution control is ended. At a tail end of the material to be rolled 2b, rolling tends to be unstable and therefore, the gap correction value and the target strip thickness correction value are not changed. For example, when the tail end is positioned LE [m] before passing through the most upstream stand to be operated, the roll force distribution modification unit 1g neither calculates a correction value nor generate a tracking point. Subsequently, the control is not performed until rolling ends.

[0215] In the present embodiment, a timing of changing a gap correction value by the mass flow thickness correction unit 1i and a timing of changing a target strip thickness correction value by the target strip thickness correction value calculation unit 1h are the same timing; however, these timings can be staggered. For example, a gap correction value is set to be changed several seconds after a target strip thickness correction value has been changed, thereby the timings for respective changes of a gap and strip thickness can be staggered.

[0216] (Work and Effect)

[0217] As described above, according to the roll force distribution control device 10, a tracking point is tracked and a gap correction value and a target strip thickness correction value are applied sequentially from an upstream side stand. By applying a gap correction value, a change in a gap error is prevented. By applying a target strip thickness correction value, a strip thickness target value on a stand delivery side is corrected so as to bring a roll force distribution ratio actual value close to a roll force distribution ratio target value.

[0218] Accordingly, an actual roll force ratio between all stands is matched with a target roll force ratio during continuous rolling, thereby a stable rolling can be achieved.

[0219] With reference to FIG. 10 and FIG. 11, one example of a control result when the roll force distribution control in the present embodiment is applied will be described.

[0220] FIG. 10 is a diagram that shows a control result over a total length of the material to be rolled 2b on an upstream side stand. An example shown in FIG. 10 is a case where a gap error that is a difference between a strip thickness actual value and a strip thickness actual recalculation value increases during rolling (10a) and after that, a mill entry side temperature rises (10g). Solid lines (4b, 4c, 7a, 7b) in FIG. 10 show control results when the roll force distribution control is not applied. Alternate long and short dash lines (10b, 10c, 10d, 10e, 10f, 10h) show control results when the roll force distribution control is applied.

[0221] First, a case where a gap error increases (10a) will be described.

[0222] In a case where a gap error that is a difference between the strip thickness actual value 7b and the strip thickness actual recalculation value 7a increases (10a), if the roll force distribution control is not applied, the roll force actual value 4b abruptly decreases and the gap actual value 4c increases.

[0223] On the other hand, when the roll force distribution control is applied, the mass flow thickness correction unit 1i calculates a gap correction value 10b for reducing the amount of change in the gap error, based on equation (22). More specifically, by increasing the gap correction value 10b in a minus direction, the gap operation unit 1d controls a rolling stand so as to reduce a roll gap. As a result of applying the roll force distribution control, an increase in the gap actual value 10c can be prevented and an abrupt decrease in the roll force actual value 10d can be prevented. At this time, the strip thickness actual recalculation value 10e based on equation (23) is prevented from decreasing in comparison with the strip thickness actual recalculation value 7a for which the roll force distribution control is not applied. In addition, the strip thickness actual value 10f for which the roll force distribution control is applied is prevented from increasing in comparison with the strip thickness actual value 7b for which the roll force distribution control is not applied. As a result, the amount of change in the gap error is reduced.

[0224] Next, a case where a mill entry side temperature rises (10g) will be described.

[0225] When a mill entry side temperature 4a increases (10g), roll force required for rolling the material to be rolled 2b decreases. Therefore, when the roll force distribution control is not applied, the roll force actual value 4b decreases. Since a final stand delivery side temperature is kept constant by finishing temperature control, the amount of decrease in the roll force of a latter stand is not as much as that of an upstream stand. Therefore, a roll force distribution ratio changes.

[0226] On the other hand, when the roll force distribution control is applied, the roll force actual values of all stands are compared and for a stand where a roll force distribution ratio actual value is smaller than a roll force distribution ratio target value, a target strip thickness correction value 10h for reducing a strip thickness target value is output. As a result, the gap operation unit 1d controls the rolling stand so as to reduce a roll gap. As a result of applying the roll force distribution control, an increase in the gap actual value 10c can be prevented and a decrease in the roll force actual value 10d can be prevented.

[0227] FIG. 11 is a diagram that shows examples of roll force actual values at the start time of rolling and before the end of rolling.

[0228] FIG. 11(A) is a graph that shows a roll force actual value 5a and a roll force distribution ratio target value 5b of each stand at the start time of rolling. When rolling starts, a roll force distribution ratio actual value which is calculated from the roll force actual value 5a of each stand matches the roll force distribution ratio target value 5b.

[0229] FIG. 11(B) is a graph that shows a roll force actual value of each stand before the end of rolling in a case where the roll force distribution control is not applied. When the roll force distribution control is not applied, control to keep the roll force distribution ratio actual value to the roll force distribution ratio target value 5b is not performed and therefore, the roll force actual value 11a of an upstream side stand shows a significant decrease in the roll force actual value of the upstream side stand due to an increase in a mill entry side temperature. The roll force of a downstream side stand does not change or on the contrary, increases under the influence of a gap error, in some cases.

[0230] FIG. 11(C) is a graph that shows a roll force actual value of each stand before the end of rolling in a case where the roll force distribution control is applied. In a case where the roll force distribution control is applied, a strip thickness target value of an upstream side stand is reduced, so that a decrease in the roll force actual value 11b of the upstream side stand can be prevented. By correcting a strip thickness target value of each stand, the roll force distribution ratio actual value can be kept to a roll force distribution ratio target value.

Second Embodiment

[0231] FIG. 12 is a diagram for describing a system configuration of a continuous rolling system according to a second embodiment of the present disclosure. The roll force distribution control device 10 according to the second embodiment includes a gap operation end intervention unit 12a in addition to the configuration shown in FIG. 1 described above. The gap operation end intervention unit 12a changes a roll gap operation value based on an intervention signal by an operator. More specifically, the gap operation end intervention unit 12a allows an operator to directly operate a roll gap.

[0232] If a roll gap operation value is changed by the gap operation end intervention unit 12a, changing of a gap correction value and a target strip thickness correction value by the roll force distribution control described above is temporarily suspended. Several seconds after the end of intervention, the roll force distribution target value is redetermined and changing the correction values by the roll force distribution control is resumed.

[0233] FIG. 13 is a diagram for describing the roll force distribution control after gap intervention. When a gap intervention in which a roll gap operation value is changed by an operator occurs (13a), a tension between stands changes due to a change in a gap and fluctuations of a force actual value occur. Therefore, the roll force distribution control device 10 stops the roll force distribution control; and neither changes the correction values nor generates a tracking point for t_gi seconds after the gap intervention.

[0234] The roll force distribution control device 10 calculates a roll force distribution ratio actual value from a roll force actual value after the gap intervention, immediately before starting the roll force distribution control after t_gi seconds have has passed. In addition, the roll force distribution control device 10 sets this roll force distribution ratio actual value as a new roll force distribution ratio target value. After that, calculation of the correction values by the roll force distribution control is resumed (13b).

[Math. 30]

γ.sub.1.sup.AIM:γ.sub.2.sup.AIM:γ.sub.3.sup.AIM: . . . :γ.sub.i.sup.AIM: . . . :γ.sub.N.sup.AIM:=P.sub.1.sup.Act:P.sub.2.sup.Act:P.sub.3.sup.Act: . . . :P.sub.i.sup.Act: . . . :P.sub.N.sup.Act   (30)

[0235] where [0236] P.sub.i.sup.Act: a roll force actual value of the i-th stand before resumption of control [kN] [0237] γ.sub.i.sup.AIM: a roll force distribution ratio target value of the i-th stand [-]

[0238] FIG. 14 is a diagram for describing an example of modifying a roll force distribution ratio target value at the time of gap intervention. In this example, the roll gap of the most upstream stand is increased to reduce a roll force actual value. The gap intervention is performed when a strip shape between stands and a stand condition are poor and therefore, a new roll force distribution ratio target value after the gap intervention is determined based on a roll force actual value that has changed due to the gap intervention as indicated by 14a. The roll force distribution control is executed so as to keep this new roll force distribution ratio target value.

[0239] As described above, for a given period of time after the gap intervention, the correction values are not changed; and after a stable state is obtained, a new roll force distribution target value is determined and the roll force distribution control is resumed. Thus, the roll force distribution is kept constant, allowing a stable rolling to be achieved.

Third Embodiment

[0240] The continuous rolling system can execute flying strip thickness change (flying gauge change: FGC) during rolling. When the flying strip thickness change is executed, the target value of product stripe thickness that is a stripe thickness target value on a final stand delivery side is changed without stopping rolling by the tandem rolling mill 2. According to the strip thickness target value on the final stand delivery side, a strip thickness target value of each stand is changed. A roll gap of each stand is changed sequentially from an upstream side stand so as to achieve the strip thickness target value of each stand.

[0241] FIG. 15 is a diagram that shows control timings of the continuous rolling system when the flying strip thickness change is executed. Before a gap change by the flying strip thickness change is performed (15a), the setting calculation unit 1c determines a strip thickness target value of each stand after the flying strip thickness change so as to allow the flying strip thickness change to be stably executed, based on the roll force distribution ratio actual value (or strip thickness actual value) of each stand before the flying strip thickness change. In addition, the setting calculation unit 1c predicts roll force after the flying strip thickness change and resets a new roll force distribution ratio target value.

[Math. 31]

γ.sub.1.sup.AIM:γ.sub.2.sup.AIM:γ.sub.3.sup.AIM: . . . :γ.sub.i.sup.AIM: . . . :γ.sub.N.sup.AIM:=P.sub.1.sup.Pre_nxt:P.sub.2.sup.Pre_nxt:P.sub.3.sup.Pre_nxt: . . . :P.sub.i.sup.Act: . . . :P.sub.N.sup.Pre_nxt   (31)

[0242] where [0243] P.sub.i.sup.Pre_nxt: a roll force prediction value after a thickness change of the i-th stand [kN] [0244] γ.sub.i.sup.AIM: a roll force distribution ratio target value of the i-th stand [-]

[0245] The entry side strip thickness influence coefficient Q.sub.i is updated.

[00004]$\begin{array}{cc}\left[\mathrm{Math}.32\right]& \\ Q_i={\left(\frac{\partial P\left(T_{\mathrm{nxt}}\left(i\right),H,h_{\mathrm{nxt}}\left(i\right),V_{\mathrm{nxt}}\left(i\right),.Math.\right)}{\partial H}\right)}^{\mathrm{CAL}}& \left(32\right)\end{array}$

[0246] where [0247] T.sub.nxt(i): entry side temperature of the i-th stand after the flying strip thickness change [degC] [0248] h.sub.nxt(i): delivery side strip thickness of the i-th stand after the flying strip thickness change [mm] [0249] V.sub.nxt(i): roll circumferential speed of the i-th stand after the flying strip thickness change [m/s]

[0250] The roll force distribution control device 10 stores a correction reference gap error before the execution of the flying strip thickness change. Since a roll gap is abruptly operated during the flying strip thickness change, the roll force distribution control is not executed before and after it. More specifically, before the flying strip thickness change is executed, calculation of the gap correction value and the target strip thickness correction value is interrupted. For example, the correction values are not changed from LE[m] before a roll gap of the most upstream stand is changed. Furthermore, the correction values are not changed until: the roll gap of each stand is changed; and the position of the material to be rolled 2b to which the change is applied advances LS[m] after passing through the strip thickness gauge 2c (15b).

[0251] The new roll force distribution ratio target value by equation (31) is updated before the roll force distribution control is resumed (15c).

[0252] In addition, since rolling conditions have changed after the flying strip thickness change, a difference between the strip thickness actual value and the strip thickness actual recalculation value abruptly changes in some cases. As a result of an abrupt change in the correction values according to the difference, if a roll gap is significantly changed, rolling may become unstable.

[0253] To prevent this abrupt change, the roll force distribution control device 10 calculates a correction reference gap error after the execution of the flying strip thickness change. More specifically, as shown in equation (35), the roll force distribution control device 10 calculates a correction reference gap error after the execution of the flying strip thickness change by adding a difference between a gap error after the flying strip thickness change and a gap error before the flying strip thickness change to a correction reference gap error before the flying strip thickness change. This updates the correction reference gap error. After the correction reference gap error is updated, the roll force distribution control is resumed and calculation of the gap correction value and the target strip thickness correction value is resumed.

[Math. 33]

S.sup.ofs_PREV(i)=S.sup.ofs(i)   (33)

[Math. 34]

S.sup.ERR_FGC(i)=h.sup.GM_FGC(i)−h.sup.MF_FGC(i)   (34)

[Math. 35]

S.sup.OFS(i)=S.sup.ofs_PREV(i)+(S.sup.ERR_FGC(i)−S.sup.ERR_PREV(i))   (35)

[0254] where [0255] S.sup.ofs_PREV(i): an offset value of the i-th stand before the flying strip thickness change [mm] [0256] h.sup.GM_FGC(i): a strip thickness actual recalculation value of the i-th stand after the flying strip thickness change [mm] (calculated at the timing 15d by using equation (11)) [0257] h.sup.MF_FGC(i): a strip thickness actual value of the i-th stand after the flying strip thickness change [mm] (calculated at the timing 15d by using equation (12)) [0258] S.sup.ERR_PREV(i): a gap error of the i-th stand before the flying strip thickness change [mm] (calculated at the timing 15e by using equation (19))

[0259] As described above, according to the control of the present embodiment, when the strip thickness is changed by the flying strip thickness change and a new roll force distribution ratio target value is given, a roll force distribution ratio actual value can be matched with a new target roll force distribution ratio.

[0260] In the above example, the flying strip thickness change for one time has been described. However, even in a case where the flying strip thickness change is executed many times during rolling, control can be performed in a similar manner to the above example.

Fourth Embodiment

[0261] A roll force distribution control device according to a fourth embodiment changes a control gain which is used for calculating a correction value in the roll force distribution control, according to the type and size of the material to be rolled 2b.

[0262] The setting calculation unit 1c receives an input of type and size information of the material to be rolled 2b from the operating instruction input unit 1b. The setting calculation unit 1c determines the use or non-use of the roll force distribution control based on the type and size information.

[0263] The setting calculation unit 1c stores in advance a table that defines a relationship between the type and size of the material to be rolled 2b and a control gain. FIG. 16 is a diagram that shows a setting example of the table. When the roll force distribution control is used, the setting calculation unit 1c obtains a parameter value corresponding to type and size information 16a from the table. The setting calculation unit 1c transmits this parameter value as a control gain to the roll force distribution modification unit 1g.

[0264] The roll force distribution modification unit 1g uses this control gain in calculation of the gap correction value and the target strip thickness correction value (equation (21), equation (27)).

[0265] According to the present embodiment, an optimum control gain according to the type and size information of the material to be rolled 2b can be applied to the calculation of the gap correction value and the target strip thickness correction value.

Fifth Embodiment

[0266] In order to stabilize a strip shape on a stand delivery side during rolling, each stand includes a shape control device (actuator) that controls the strip shape. For example, a bending device can control the strip shape by applying pressure to work roll ends to correct deformation of a roll. In addition, a work roll shift device can control the strip shape by shifting work rolls provided with an initial curve to change a width direction distribution of a roll gap.

[0267] Control of the strip shape is also possible by changing the deformation of the roll by changing the roll force of a stand. Therefore, in the present embodiment, when an output of the shape control device reaches its limit, roll force is changed by changing the roll force distribution ratio for the stand, thereby correcting the strip shape.

[0268] For example, the roll force distribution ratio for the i-th stand in which outputs of a bending device and a work roll shift device reach their limit values is modified. When a bending force is increased, pressure is applied in a direction of opening roll end portions and therefore, the amount of change in the strip thickness at the roll end portions is reduced. On the other hand, when roll force is reduced, roll deformation is reduced and therefore, the amount of change in the strip thickness at strip end portions is reduced. Therefore, when a roll bending force reaches the mechanical or operational maximum value during rolling, the roll force distribution ratio for the stand is reduced to determine a new roll force distribution ratio target value.

[Math. 36]

γ.sub.1.sup.AIM(new):γ.sub.2.sup.AIM(new):γ.sub.3.sup.AIM(new): . . . :γ.sub.i.sup.AIM(new): . . . :γ.sub.N.sup.AIM(new):=γ.sub.1.sup.AIM:γ.sub.2.sup.AIM:γ.sub.3.sup.AIM:−γ: . . . :γ.sub.i.sup.AIM: . . . :γ.sub.N.sup.AIM   (36)

[0269] where

[0270] Δγ: the amount of change in a roll force distribution ratio [-]

[0271] Thus, the roll force distribution control device 10 changes the roll force distribution ratio target value of a stand having a shape control device in a direction of reducing an output of the shape control device when the output reaches an upper limit value and in a direction of increasing an output of the shape control device when the output is reaches a lower limit value. According to this control, even when an output of the shape control device reaches a limit value, the strip shape can be improved by changing the roll force distribution ratio target value.

Sixth Embodiment

[0272] In the third embodiment, a gap error that occurs during FGC is integrated and stored to prevent an abrupt change. By transferring a gap error S.sup.OFS(i) to a gap correction value ΔS.sup.COMP(i) in stages, a gap error that occurs during changing of strip thickness by flying strip thickness change can be reduced gradually with time.

[Math. 37]

chgovr0=α(i).Math.S.sup.OFS(i)   (37)

[Math. 38]

chgovr=Clamp(chgovr0,ΔS.sup.COMP_UL(i)−ΔS.sup.COMP(i),ΔS.sup.COMP_LL(i)−ΔS.sup.COMP(i))   (38)

[Math. 39]

ΔS.sup.COMP(i)=ΔS.sup.COMP(i)+chgovr   (39)

[Math. 40]

S.sup.OFS(i)=S.sup.OFS(i)−chgovr   (40)

[0273] where [0274] α(i): a transfer gain (adjustment value, for example, 0.1) (0≤β≤1.0)

[0275] The roll force distribution control device 10 reduces a gap error S.sup.OFS(i) that occurs during FGC by using the above equation including the transfer gain α(i); and transfers a reduction amount to the gap correction value ΔS.sup.COPM(i). As a result, a difference between a strip thickness actual value and a strip thickness actual recalculation value (gap error) can be reduced.

[0276] (Hardware Configuration Example)

[0277] FIG. 17 is a conceptual diagram that shows a hardware configuration example of a processing circuit included in the roll force distribution control device 10 in each of the embodiments described above. Each of the above-mentioned functions is achieved by the processing circuit. In one aspect, the processing circuit includes at least one processor 91 and at least one memory 92. In another aspect, the processing circuit includes at least one piece of dedicated hardware 93.

[0278] In a case where the processing circuit includes the processor 91 and the memory 92, each of the functions is achieved by software, firmware, or a combination of the software and firmware. At least either the software or firmware is described as a program. At least either the software or firmware is stored in the memory 92. The processor 91 reads and executes a program stored in the memory 92, thereby implementing each of the functions.

[0279] In a case where the processing circuit includes the dedicated hardware 93, the processing circuit is, for example, a single circuit, a composite circuit, a programmed processor, or a combination of them. Each of the functions is provided by the processing circuit.

[0280] Although the embodiments according to the present disclosure have been described above, the present disclosure is not limited to the above embodiments and various modifications can be made without departing from the scope of the present disclosure. The configurations of the embodiments can be combined.

REFERENCE SIGNS LIST

[0281] 1b Operating instruction input unit

[0282] 1c Setting calculation unit

[0283] 1d Gap operation unit

[0284] 1e Actual data collection unit

[0285] 1f Target strip thickness operation unit

[0286] 1g Roll force distribution modification unit

[0287] 1h Target strip thickness correction value calculation unit

[0288] 1i Mass flow thickness correction unit

[0289] 1j Tracking unit

[0290] 2 tandem rolling mill

[0291] 2a Rolling stand

[0292] 2b Material to be rolled

[0293] 2c Strip thickness gauge

[0294] 3a Work roll

[0295] 3b Backup roll

[0296] 3c Hydraulic cylinder

[0297] 3d Load cell

[0298] 3e Encoder

[0299] 4a Mill entry side temperature

[0300] 4b Roll force actual value

[0301] 4c Gap actual value

[0302] 4d Delivery side strip thickness

[0303] 5a Roll force actual value

[0304] 5b Roll force distribution ratio target value

[0305] 5c Roll force distribution ratio actual value

[0306] 7a Strip thickness actual recalculation value

[0307] 7b Strip thickness actual value

[0308] 10 Roll force distribution control device

[0309] 10b Gap correction value

[0310] 10c Gap actual value

[0311] 10d Roll force actual value

[0312] 10e Strip thickness actual recalculation value

[0313] 10f Strip thickness actual value

[0314] 10h Target strip thickness correction value

[0315] 11a, 11b Roll force actual value

[0316] 12a Gap operation end intervention unit

[0317] 16a Type and size information

[0318] 20 Rolling line

[0319] 91 Processor

[0320] 92 Memory

[0321] 93 Hardware