Mass flow regulation in roller devices

Abstract

A method for controlling a roller line, preferably a cold roller line, which has one or more roller stands each with two working rollers, which form a roller gap, through which a roller band is transportable. One or both working rollers can shift relative to the other, so that the roller gap is adjustable. The method includes making available a reference speed, which is a parameter for controlling the roller line, measurement of speed of the roller band before the inlet into the roller gap, measurement of the thickness of the roller band before the inlet into the roller gap, and adjustment of the roller gap of one or more roller frames in the roller line on the basis of measured speed and thickness before the inlet into the roller gap as well as the reference speed.

Claims

1. A method for controlling a roller line, which has one or more roller stands each with two working rollers, which form a roller gap, through which a roller band is transportable, wherein one or both working rollers can shift relative to the other, so that the roller gap is adjustable, wherein the method comprises controlling the roller line by performing the steps of: determining a reference speed, which is a parameter for controlling the roller line; measuring a speed of the roller band before an inlet into a first roller gap; measuring a thickness of the roller band before the inlet into the first roller gap; and adjusting one or more roller gaps of one or more roller stands in the roller line on the basis of the measured speed and the thickness before the inlet into the first roller gap as well as the reference speed, wherein the controlling of the roller line is carried out without taking into account any measured or calculated outlet side band speed at a last roller stand of the one or more roller stands, and further comprising: determining a reference band thickness, which is a parameter for controlling the roller line, and before the adjusting of the one or more roller gaps, computing a thickness deviation of the roller band as follows: $h_{\mathrm{iDevCalc}}\left(t\right)=\frac{h_{\mathrm{iTrk}-1}\left(t\right)*v_{i-1}\left(t\right)}{v_{\mathrm{iR}}\left(t\right)}-h_{\mathrm{iR}}$ wherein: h.sub.iDevCalc(t)=the thickness deviation of the roller band, h.sub.iTrk1(t)=the thickness at an inlet of any roller stand, v.sub.i1(t)=the measured speed, v.sub.iR(t)=the reference speed, and h.sub.iR=the reference band thickness.

2. The method of claim 1, wherein the reference speed corresponds to a target speed at which the roller band is to be transported through the roller line, or is a speed parameter with which one or more rollers, a return pulley or a winch, are controlled in the roller line.

3. The method of claim 1, further comprising: measuring an outlet-side band thickness at the one or more roller stands, for each roller stand in the one or more roller stands, determining a measured thickness deviation based on an inlet-side band thickness and the outlet-side band thickness across said each roller stand, and comparing the measured thickness deviation with the computed thickness deviation.

4. The method of claim 1, wherein the reference band thickness is a target thickness upon exiting the roller line.

5. The method of claim 1, wherein the thickness of the roller band at the inlet of one roller stand is measured and the reference band thickness is used for adjusting the roller gap of one or more subsequent roller stands of the one or more roller stands in a transport direction of the roller line.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) FIG. 1 is a schematic depiction of a tandem line with four roller stands situated one after the other.

(2) FIG. 2 is a schematic depiction of a roller stand with two supporting rollers and two working rollers.

DETAILED DESCRIPTION

(3) In what follows, preferred embodiments are described, employing the figures. With this, similar or identically acting elements are provided with identical reference symbols, and in part a repeated description of these elements is dispensed with, to avoid redundancies.

(4) FIG. 1 is a schematic depiction of a tandem line or roller line 1 with four roller stands 10 situated one behind the other, preferably for a cold roller line. Roller line 1 in the current example has an unwinding winch 2 and a takeup winch 3. A roller band or roller stock B is fed to roller stands 10 in transport direction R, if necessary via return pulleys, and after passing roller stands 10, i.e. after completion of the roller processing, is wound up by takeup winch 3. The feeding and removal of roller band B via winches 2 and 3, is only an example; roller band B can also be brought to roller stands 10 by another means and be removed for further processing, for transport, etc.

(5) To distinguish the roller stands 10, they are given consecutive numbers in transport direction R of roller band B, i.e. in the FIG. 1 view, from right to left. Each roller stand 10 has two support rollers 11 and two working rollers 12. It should, however, be noted that the method depicted can be implemented and is suitable for all stand arrangements with two or more rollers per stand. For the sake of clarity, reference symbols 11 and 12 are not drawn in in FIG. 1, but they are revealed in FIG. 2, in which one roller stand 10 is chosen and shown in an enlarged manner. One working roller 12 is in contact with each support roller 11. Between the two working rollers 12 there is a roller gap, through which roller band B is guided. The roller gap is adjustable, in that one or both of the working rollers 12 that form the roller gap is adjustable relative to each other. Working rollers 12 and/or support rollers 11 are for example driven by one or more electric motors (not shown in the figures) in rotating fashion, if necessary by interposing a drive, a clutch, a brake, etc. For this purpose, the roller stands 10 each have a drive controller 33.

(6) Before first roller stand 10, before second and after fourth roller stand 10, a thickness measuring device 20 is situated, which is installed for measurement of the thickness of roller band B at the particular position. In the present embodiment, to each roller stand 10, a thickness controller 30 is assigned, which communicates with a gap controller 31 for adjusting the gap between the particular working rollers 12. Additionally, in the present example, before each roller stand 10 a tension regulator 22 is situated, which has an actuator to alter the adjustment of roller band B relative to roller stand 10. An adjustment alteration is used to regulate the inlet-side tension of roller band B. A change in tension is to be equated with a change in speed of roller band B. The tension regulators 22 of second to fourth roller stands 10 each have a tension controller 32 for setting the adjustment.

(7) Possible communication paths between controllers 30, 31, 32, 33 and the pertinent actuators, motors, etc. are schematically drawn in FIG. 1. The communication can occur in physical or in wireless fashion. Even if controllers 30, 31, 32, 33 in FIG. 1 are depicted separately, they naturally can be configured to be integrated or perhaps as part of a central control. The designation of device in this connection does not necessarily mean a mechanical entity, because controllers 30, 31, 32, 33 can also be implemented using software which controls roller line 1, if it is implemented on a computer.

(8) The gap of the particular roller stand 10 is adjusted via a mass flow control. The starting point is a conservation quantity, the product of the band speed and the band thickness shifted in the roller gap, which is designated as a mass flow quantity and is altered with passage of roller band B through roller stand 10 or example analogous to an inlet-side thickness disturbance or alteration of other process quantities such as band strength, gap friction and/or band speed.
v.sub.i(t)*h.sub.i(t)=v.sub.i1(t)*h.sub.i1(t)

(9) With this, v.sub.i(t) designates the band speed at the outlet of roller stand 10 (equal to band speed at the inlet of any following roller stand 10) as a function of time. h.sub.i(t) designates the measured band thickness at the outlet of roller stand 10 (equal to the roller band thickness at the inlet of any following roller stand 10) as a function of time. v.sub.i1(t) designates the band speed measured on the inlet side about roller stand 10 as a function of time, and h.sub.i(t) designates the measured band thickness on the inlet side about roller stand 10. The equation is valid for all roller stands 10 in a roller line 1, the i in the designations is a whole number for consecutive numbering of the individual roller stands 10.

(10) If an outlet-side reference band thickness is designated by h.sub.iR(t) and h.sub.iDev(t) designates the outlet-side band thickness deviation, i.e.,
h.sub.i(t)=h.sub.iR(t)+h.sub.iDev(t)
there follows:

(11) $h_{\mathrm{iDev}}\left(t\right)=\frac{h_{i-1}\left(t\right)*v_{i-1}\left(t\right)}{v_i\left(t\right)}-h_{\mathrm{iR}}$

(12) The reference band thickness is a parameter for guidance of the roller line. Thus, the reference band thickness can be that target thickness that is striven for the roller band after passage of the roller line, especially if the roller line, after the startup, is in a stationary or quasi-stationary state. The reference band thickness can for example be set in advance, it can be constant or a function of time, and/or of the band length.

(13) Now instead of measuring v.sub.i(t) conventionally, such as by means of a laser, or from de facto quantities of roller line 1, such as computing winch speed or working roller speed, for computation of the mass flow thickness a reference speed at the outlet v.sub.iR(t) is used. This is possible because the effects of an adjustment change of roller band B relative to roller stand 10 through tension regulator 22 can be neglected. The change in outlet speed merely contains the forward slip change evoked by the adjustment change, which is very small in relation to the absolute change, especially in the speed ranges in which a mass flow control is carried out.

(14) The reference speed v.sub.iR(t) can therefore be a speed parameter by which roller line 1 is controlled. Therefore, measurement or computation of a speed while using a measured quantity that corresponds to the speed at the outlet of the roller gap, can be dispensed with. The reference speed v.sub.iR(t) can for example be a target speed at which roller band B is to be transported through roller line 1, perhaps if the roller line 1 after startup is in a stationary or quasi-stationary state. The reference speed v.sub.iR(t) can for example also be a speed parameter by which a roller, preferably working roller 12, or a winch, is guided in roller line 1. The reference speed can be set in advance, it can be constant or a function of time or of the band length. The reference speed can, but must not, contain one or more correction values from other control systems. These correction values can for example consist of or be computed from control corrections of tension, band thickness and/or of speed guidance. These correction values can, for example, consist of or be computed from control corrections of tension, band thickness and/or of the speed guidance.

(15) From this follows the computed band thickness deviation h.sub.iDevCale(t) in the i'th roller stand 10,

(16) $h_{\mathrm{iDevCalc}}\left(t\right)=\frac{h_{\mathrm{iTrk}-1}\left(t\right)*v_{i-1}\left(t\right)}{v_{\mathrm{iR}}\left(t\right)}-h_{\mathrm{iR}}$

(17) Where h.sub.iTrk1(t) designates the inlet-side (on the i'th roller stand 10) measured band thickness of roller band B.

(18) Roller band 10 with the band thickness deviation thus computed, is then transferred or transported to the outlet-side thickness measuring device 20. This computed hand thickness deviation, transported on to the thickness measurement device 20 at the outlet is compared with the thickness deviation measured at the outlet. The error is tracked, this being done likewise with the reference speed v.sub.iR(t).

(19) In this way, thickness errors can be tracked, and the target thickness at the end of roller line 1 is reached. The difference between the de facto thickness of roller band 10 at the end of roller line 1 and the desired thickness can be stabilized for example by a PI controller or PID controller, as also by a feedback via a filter unit.

(20) According to another embodiment, the mass flow control can also be run without tracking of the outlet-side thickness, i.e., exclusively with the inlet-side thickness and speed measurement as per:

(21) $h_{\mathrm{iDevCalc}}\left(t\right)=\frac{h_{\mathrm{iTrk}-1}\left(t\right)*v_{i-1}\left(t\right)}{v_{\mathrm{iR}}\left(t\right)}-h_{\mathrm{iR}}$

(22) With this, in a roller line 1 with multiple roller stands 10 (a tandem line), in addition to doing away with an outlet-side speed measurement in the first roller stand 10, thickness measurement can also be dispensed with on the outlet side. In this case the thickness control in the last roller stand 10 can stabilize the thickness offset, to be able to come to the desired target thickness. All dynamic disturbances, such as irregularities in inlet thickness and/or variations in hardness, can be stabilized already from the first roller stand 10 according to a variant of this embodiment. Although a measurement of thickness after the first roller stand 10 is not absolutely necessary in this version, nonetheless an appropriate thickness measurement device can be provided, to provide a fallback option in case the inlet-side thickness measurement fails.

(23) Through the embodiments depicted for mass flow thickness regulation, measurement or computation of speed of toiler band B at the outlet of one or more roller stands 10 can be dispensed with. Costs can thereby be saved which otherwise would accrue to setup, installation, maintenance, etc. of the corresponding sensors and electronic devices. The control is less impaired by measurement error, which especially can appear with a speed measurement at the outlet of first roller stand 10, perhaps due to slip between the roller stock and measurement roller unit, emulsion or oil on the measured stock, vapor or lack of space, for example if a laser is used for measurement. The reliability of thickness regulation is increased, which in turn has an effect on the quality of the rolled product to be manufactured. Especially with facilities having difficult installation situations, the described control makes possible regulation of thickness with high dynamics and direct reaction in the roller gap.

(24) The control or regulation is especially preferably applicable for cold rolling lines for rolling band-shaped metallic materials, especially metallic bands of steel or nonferrous metals (NF) metals.

(25) If applicable, all the individual features that are described in the embodiments, can be combined with each other and/or exchanged, without departing from the scope of the invention.

LIST OF REFERENCE SYMBOLS

(26) 1 Roller line 2 Unwinding winch 3 Takeup winch 10 Roller stand 11 Support roller 12 Working roller 20 Thickness measuring device 22 Tension regulator 30 Thickness controller 31 Gap controller 32 Tension controller 33 Drive controller B Roller band R Transport direction