JPH02165809A - Controller for speed detection roll for rolled strip - Google Patents

Abstract

PURPOSE:To accurately detect a strip speed by separately selecting control modes in both the back tension and the forward tension sides. CONSTITUTION:A strip 2 rewound from an inlet side reel 1 is supplied to a rolling mill 5 through a back tension side speed detection roll 3 and a sheet thickness detector 4 using X-ray, etc., and then the strip 2 is wound on an outlet side reel 8 after respective detections by a sheet thickness detector 6 and a speed detection roll 7 in the forward tension side. In that time, a driving motor MB in the back tension side is controlled by an electric current control mode based on electric currents given to the motor MB. A driving motor MF in the forward tension side is controlled based on rotating speeds of a deflector roll 7. Therefore, the deflector roll 7 is controlled with stability and no slip.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for controlling the drive of a speed detection roll in a rolling mill.

[Prior art] Conventionally, plate speed detection in the rolling process was performed using mass flow AG.
C, and for this purpose a board speed detection roll (
A deflector roll) is brought into contact with the strip to detect the speed. In this case, the plate speed detection roll is mostly used in an idle state, and when the frictional force between the plate and the deflector roll decreases, especially when the front and rear tension is low, the friction between the plate and the roll decreases. When the coefficient decreases, slip occurs, which has an adverse effect on mass flow AGC, etc. This tendency is particularly noticeable during line acceleration and deceleration.

As a countermeasure, the deflector roll is driven by a motor,
There is a method of controlling the motor using current control or a speed control system with drooping (drooping characteristics).

[Problem to be solved by the invention] However, the above method has the following problems.

(1) Problems with the current control method As shown in Figure 8, when driving the motor, the current target value is given as a function of mechanical loss, and the acceleration/deceleration current (inertia of the deflector roll during acceleration/deceleration) moment compensation bone) is given. However, mechanical loss tends to fluctuate due to various causes, and when the current target value is given as a function of the initial setting value, if the frictional force between the strip and the deflector roll decreases and slip occurs, the deflector roll will change. Acceleration (current target value 〉 actual mechanical loss) or deceleration (current target value 〈 actual mechanical loss)
The speed limit circuit operates and the speed of the deflector roll increases to the speed limit bias of the line speed. For example, the speed limit bias is 10 to 1 of the maximum speed.
In order to have 5%, if a slip occurs during operation at 200mpm on a line with a maximum speed of 1000mpm, 200 + 1000X (10~15%) ~ 300~3
The speed increases to 50mpm. For this reason, accurate stripping speed cannot be measured, and the error thereof is also very large.

(2) Problems with the drooping + speed control method When driving the deflector roll, there is no need to perform external work such as conveying the strip, so the motor capacity may be small. Therefore, in order to prevent the motor from tripping due to load fluctuations on the load side, it is necessary to provide drooping as shown in FIG. 9. However, as shown in Figure 10, when the lead rate is zero, no current flows in the steady state (total target speed totalvt
, l=feedback speed VFII), so the movement is the same as the conventional idle roll, and has no effect on slipping at all.

Also, since an accelerating current flows during acceleration/deceleration, the total target speed 101alVr=+=target speedvr,, -■pn"
X8%, which gives a total target speed lower than the strip speed, resulting in a state where slipping is likely to occur.

As a countermeasure for this, it is conceivable to multiply the deflector roll alone by a lead rate to compensate for its own mechanical loss, as shown in FIG. 1A.

The lead rate biases the strip speed to compensate for the cancellation caused by drooping. However, since the read rate is preset and the drooping amount changes depending on the load condition, it is impossible to use it without both. This is because their personalities are completely different. If the lead ratio is set to an appropriate value, the deflector roll will flow its own mechanical loss compensation bone and acceleration/deceleration current, making it possible to create a control system that is resistant to slips.

In any case, in the past, there was a choice between current control and speed control, and sufficient consideration was not given to the above points.

An object of the present invention is to provide a speed detection roll control device that can accurately detect strip speed.

[Means for Solving the Problems] The present invention for solving the above problems includes providing deflector rolls on the back tension side and the forward tension side of a rolling mill, respectively, for contacting the strip and detecting its moving speed. In addition, in equipment in which each deflector roll is rotationally driven by a drive motor in accordance with the moving speed of the strip; a current control method that controls the drive motor on the back tension side based on the current applied thereto, and a current control method on the forward tension side. The drive motors of the deflector rolls are controlled by a speed control method based on the rotational speed of the deflector roll.

[Function] Generally, the back tension side is always in a high tension state (usually 1
3 to 25 tons), the frictional force between the deflector roll and the strip is very large, making it difficult for slips to occur. Additionally, speed control and current control have significantly different responsiveness, with current control being faster. For example, in speed control, 10~
30 rad/sec, current control: 70 to 300 r
ad/see. Also, the back tension side is AGC
Due to the correction, the reverse rate changes more than the forward rate (lead rate), resulting in severe speed fluctuations. In the present invention, since the drive control of the deflector roll on the back tension side is performed by current control, response is quick and stable control without slip is possible.

On the other hand, on the forward tension side, winding is performed at a low tension due to limitations on the appropriate winding tension of the coil, so slippage is likely to occur. Furthermore, on the forward tension side, fluctuations in the lead rate are small and the speed is stable. In the present invention, the drive control of the forward tension side deflector roll is performed based on the rotational speed of the deflector roll, which has a control system that is resistant to slips, so that the deflector roll can be controlled stably and without slipping.

[Specific structure of the invention] Hereinafter, the present invention will be explained in more detail based on the drawings.

FIG. 2 is a schematic diagram of reverse rolling. The strip 2 unwound from the input reel 1 is sent to a rolling mill 5 via a speed detection roll 3 on the back tension side and a plate thickness detection device 4 using X-rays or the like on the back tension side, and is then sent to a rolling mill 5 to detect the plate thickness on the forward tension side. After the speed is detected by the detection device 6 and the forward tension side speed detection roll 7, it is wound onto the exit side reel 8. In the present invention, the drive of both speed detection rolls 3.7 is controlled as follows.

First, FIG. 1A is a diagram showing the control of the deflector roll 3 on the back tension side. First, the target speed V r e
Given I, the pre-created mechanical loss VS
In the speed mechanical loss conversion table IO, target currents ①, 8. is calculated, and the acceleration/deceleration compensation signal is added to the total target current total I. , is calculated. Next, the target current signal total I, -t is input to the motor MB via the current control device 11 to drive the back tension side deflector roll 3. A current detector 12 is provided between the current control device 11' and the motor MB.
is provided to control the current while feeding back the current current to the total target current signal.

On the other hand, to explain the drive control of the speed detection roll on the forward tension side with reference to FIG. 1B, first, for a given target speed V, A rate signal is output, and this and a drooping signal, which will be described later, are added to the target speed value V□, to obtain a total target speed of 1otalv,s.
get r. Then, this total target speed signal total v
rat is subtracted by the speed feedback signal VP11 obtained from the rotary motor 21 that detects the rotational drive of the drive motor MF that drives the deflector roll 7, and then inputted into the speed control device 22 to obtain the target current value I. ,
. .

After that, the current feedback signal Irn from the current detector 23 is subtracted, and then the current control device 24 drives the motor MF to drive the forward tension side deflector roll 7. The signal from the current detector 23 is the target current value I. , and a drooping setting device 25 applies drooping to the total target speed value totalvre+. The speed signal V□ from the forward tension side rotary generator 21 is fed back to the total target speed value total V re I, and also fed back to the lead rate correction table 20 to calculate the lead rate.

By the way, if the lead rate is constant, if a change in mechanical loss occurs, the total target speed will no longer match the stripping speed, and slipping will occur easily. Therefore,
It is desirable to correct the read rate according to changes in mechanical loss.

For this purpose, a lead rate correction signal is input into the lead rate correction table 20. This lead rate correction signal includes the drive speed from the rotary generator 13 attached to the drive motor MB, the drive speed from the rotary generator 21, the plate thickness detection device 4.
This is given by a slip detector 30 that calculates the amount of slip, mechanical loss, and correction amount of lead rate obtained based on each plate thickness signal from 6. This slip detector 30
The mechanical loss correction signal calculated by is given to the mechanical loss correction table 10 as a mechanical loss correction signal.

In a speed control system, if the lead rate is optimal, the control system will be extremely resistant to slips, but if it is inappropriate, it will cause slips. In this embodiment, as described above, the read rate is given after being corrected as a function of mechanical loss.

Originally, it is optimal for the lead rate to correct the target speed reduction due to drooping (drooping a% x current for mechanical loss) which is affected by the current for mechanical loss of the deflector roll. However, although some equipment has a constant mechanical loss, it usually changes depending on the line speed and is not constant.

Therefore, in this embodiment, the lead is changed depending on the line speed as shown in FIG. Note that the optimum lead rate is given by mechanical loss X% x a (drooping)%.

Furthermore, if the lead rate is kept constant as in the past, the mechanical loss current required in the lead rate region smaller than the optimum lead rate does not flow, so the strip moves in the direction of being pulled by the strip and tends to slip in the lag direction. . Further, in a read rate region larger than the optimum read rate, a current higher than the mechanical loss current flows, and the strip tends to slip in the advance direction with respect to the strip speed. By such lead rate correction, only the mechanical loss of the deflector roll flows, and a control system that is always resistant to slipping can be achieved.

Although a control system that is sufficiently strong against slips has been constructed in this way, it does not have the ability to correct changes in mechanical loss over time.

Therefore, it is desirable to detect slip and correct mechanical loss and lead rate based on mass flow AGC as described below.

In Fig. 2, when the inlet speed of the rolling mill is VB, the outlet speed is vl, and the inlet plate thickness is HX, the outlet mass 7O-A
The GC plate thickness hM is given by hM=Vp xHx/vo. Since this mass flow AGC plate thickness is the plate thickness immediately under mill rolling, slip can be detected by tracking this plate thickness and comparing it with the outlet plate thickness as shown in FIG.

When slip is detected in this way, Δε is multiplied by a gain as shown in FIG. Add correction to. In this case, the correction gain is set to a low gain because the pack tension side deflector roll is less likely to slip, and a high gain is set to the forward tension side deflector roll because it is more likely to slip. It is preferable to do so. Further, as shown in the same figure, in order to prevent sudden changes in the table value of the longitudinal speed, it is preferable to perform correction by linear approximation to the table value at 10% points before and after the slip occurrence speed.

[Example] Next, the effects of the apparatus of the present invention will be clarified by comparing the above-mentioned present invention and the conventional method.

That is, to obtain a low carbon cold rolled steel plate, a 2.3 positive plate was reverse rolled to a width of 0.5 mm x 1005 m. The number of passes is 5. The deflector roll used had a diameter of 313 mm and a length of 120 mm (1 m).

The case of the present invention is shown in FIG. 6, and the conventional example is shown in FIG. It can be seen that the exit plate thickness accuracy in the final pass has been improved.

[Effects of the Invention] As described above, according to the present invention, since the control methods are selected for each of the pack tension side and the forward tension side, it is possible to accurately detect the stripping speed.

[Brief explanation of the drawing]

FIG. 1A is an explanatory diagram of the current control system of the drive motor of the speed detection roll on the pack tension side according to the present invention, FIG. 1B is an explanatory diagram of the speed control system of the drive motor of the speed detection roll on the forward tension side, and FIG. The figure is a schematic diagram of the reverse rolling equipment, Figure 3 is a diagram of the relationship between line speed and lead ratio, and Figure 4 is a diagram of the relationship between line speed and lead ratio.
FIG. 5 is a diagram showing the slip detection mechanism, FIG. 5 is a diagram showing the lead rate correction method, FIG. 6 is a diagram showing the effect of the device of the present invention,
Figure 7 is a diagram showing the effects of the conventional device, Figure 8 is a diagram of conventional current control, Figure 9 is a diagram of conventional speed control, and Figure 1O is a diagram of the relationship between stripping speed, lead rate, and current. be. ■...Entry side reel, 2...Strip, 3...Back tension side deflector roll, 5...Rolling roll, 7...Forward tension side deflector roll, 8...Output reel . Line, 2 degrees

Claims (1)

[Claims] (1) Deflector rolls are provided on the back tension side and forward tension side of the rolling mill to contact the strip and detect its moving speed, and each deflector roll is driven to rotate by a drive motor in accordance with the moving speed of the strip. A current control method that controls the drive motor on the back tension side based on the current applied to it
1. A speed detection roll control device for rolling strip, characterized in that the drive motors on the forward tension side are each controlled by a speed control method that controls the drive motors based on the rotational speed of the deflector roll.