JPH0551369B2 - - Google Patents

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 is used for mass flow AGC, and for this purpose, a plate speed detection roll (deflector roll) is brought into contact with a 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 coefficient between the plate and the roll decreases. When the flow rate decreases, slip occurs, which has a negative impact on mass flow AGC, etc. This tendency is particularly noticeable during line acceleration and deceleration.

As a countermeasure, there is a method in which the deflector roll is driven by a motor, and the motor is controlled by current control or a speed control system with drooping (drooping characteristics).

[Problems 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 given by the mechanical loss function and the acceleration/deceleration compensation (moment of inertia of the deflector roll during acceleration/deceleration) compensation) is given. However, mechanical loss tends to fluctuate due to various causes, and if the target current 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 is accelerated (current target value > actual mechanical loss) or decelerated (current target value < actual mechanical loss), and the speed limit circuit operates and the speed of the deflector roll is reduced to line speed + speed limit bias. It will rise. For example, the speed limit bias has 10-15% of the high speed, so on the maximum 1000mpm line,
If a slip occurs while driving at 200mpm,
Increases to 200 + 1000 x (10-15%) = 300-350mpm. For this reason, it is not possible to accurately measure the stripping speed, and the error is also very large.

(2) Problems with the drooping + speed control method When driving the deflector roll, there is no need for external work such as conveying the strip, so the motor capacity can be small. Therefore, in order to prevent the load from tripping due to load fluctuations on the load side, as shown in Figure 9,
It is necessary to add drooping. However, as shown in Figure 10, when the read rate is zero, no current flows in the steady state (total target speed totalv _ref = feedback speed
v _FB ), so the movement is the same as a conventional idle roll, and has no effect on slips.

Also, since acceleration current flows during acceleration/deceleration, total target speed totalv _ref = target speed v _ref −I _FB ^* ×
a%, and a total target speed lower than the strip speed is given, resulting in a state in which slips are 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 allow its own mechanical loss compensation and acceleration/deceleration current to flow, 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 method that can accurately detect the strip speed.

[Means for Solving the Problems] The present invention for solving the above problems provides deflector rolls on the back tension side and the forward tension side of a rolling mill, which contact the strip and detect its moving speed. In the method in which each deflector roll is rotationally driven by a drive motor in accordance with the moving speed of the strip, there is a current control method in which the drive motor on the back tension side is controlled based on the current applied thereto, and a current control method is used 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 13 to 25 tons), so the frictional force between the deflector roll and the strip is very large, making it difficult to slip. Additionally, speed control and current control have significantly different responsiveness, with current control being faster.
For example, speed control is 10 to 30 red/sec, and current control is 70 to 300 rad/sec. Also, on the back tension side, due to AGC correction, the reverse rate changes more than the forward rate (lead rate), resulting in severe speed fluctuations. In the present invention, since the drive of the deflector roll on the back tension side is controlled by current control, the response is quick and stable control without slip is possible.

On the other hand, the forward tension side is susceptible to slipping because low-tension ticket taking is performed due to limitations on the appropriate ticket taking tension of the coil. Furthermore, on the forward tension side, fluctuations in the read rate are small and the speed is stable. In the present invention, the drive of the forward tension side deflector roll is controlled 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] The present invention will be explained in more detail below 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. After the speed is detected by the plate thickness detecting device 6 on the side and the speed detecting roll 7 on the forward tension side, the sheet is wound onto the exit reel 8. In the present invention, the driving of both speed detection rolls 3 and 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, when the target speed v _ref is given, the mechanical loss conversion table 10 of mechanical loss vs. speed created in advance is shown in FIG. 1B. Calculate the target current _Iref in response to the mechanical loss correction signal from the slip detector 30 shown in FIG.
By adding the acceleration/deceleration compensation signal to this, the total target current is calculated.
Calculate totalI _ref . Then the target current signal
totalI _ref is sent to the motor MB via the current control device 11.
is input to drive the deflector roll 3 on the back tension side. The above current control device 11 and motor
A current detector 12 is provided between the MBs, and the current is controlled 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. A rate signal is output, and this and a Dru Pink signal, which will be described later, are added to the target speed value v _ref to obtain the total target speed totalv _ref . This total target speed signal totalv _ref is then subtracted by the speed feedback signal v _FB obtained from the rotary motor 21 which detects the rotary drive of the drive motor MF that drives the deflector roll 7, which is then sent to the speed control device 22. After inputting and setting the target current value I _ref ,
Current feedback signal from current detector 23
_IFB is subtracted, and then the motor MF is driven by the current control device 24, and the deflector roll 7 on the forward tension side is driven. Current detector 23
The signal from is fed back to the target current value I _ref , and a drooping setting device 25 applies drooping to the total target speed value totalv _ref . The speed signal v _FB from the forward tension side rotating generator 21 not only feeds back to the total target speed value totalv _ref , but also uses the lead rate correction table 2 mentioned above.
0 as well to calculate the lead rate.

By the way, if the read rate is constant, if a change in mechanical loss occurs, the total target speed will no longer match the strip speed, making it easy to slip. 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 is a slip rate obtained based on 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 signals from the plate thickness detectors 4 and 6, etc. It is given by the slip detector 30 which calculates the amount of correction for the amount, mechanical loss, and lead rate. This slip detector 30
The mechanical loss correction signal calculated by is given to the mechanical loss conversion 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.
Improper use may 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 there are some facilities where mechanical loss is constant, it usually changes depending on the line speed.
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 held 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, causing the strip to slip in the direction of delay. Easy to do. Further, in a read rate region where the optimum read rate is large, a current higher than the mechanical loss current flows, and the strip tends to slip in the advancing 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 slips and correct mechanical loss and read rate based on mass flow AGC as described below.

In Fig. 2, when the inlet speed of the rolling mill is V _E , the outlet speed is V _D , and the inlet plate thickness is H _X , the outlet mass flow AGC plate thickness h _M is h _M = V _E ×H _X /V _D is given by Since this mass flow AGC plate thickness h _M is the plate thickness immediately under rolling, this plate thickness is tracked and the difference Δε from the exit plate thickness _h As a result of the above, slips can be detected.

If a slip is detected in this way,
As shown in Fig. 5, the output Δy after giving a dead band to Δε is multiplied by the gain, and the mechanical loss conversion table 1 of the deflector roll on the back tension side is calculated.
Correction is added to the lead rate correction table 20 for the deflector rolls on the zero and forward tension sides. In this case, the correction gain is set to a low gain because the deflector roll on the back tension side is less likely to slip, and the correction gain is set to a high gain because the deflector roll on the forward tension side is more likely to slip. It is preferable that Further, as shown in the 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 of the slip occurrence speed.

[Example] Next, an example will be shown to clarify the effects of the present invention by comparison with a conventional method.

In other words, in obtaining low carbon steel cold rolled steel sheets,
A 2.3 mm plate was reverse rolled to a width of 0.5 mm x 1005 mm. The number of passes is 5. The deflector roll used had a diameter of 313 mm and a length of 1200 mm.

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 back tension side and the forward tension side, it has become 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 back tension side according to the present invention, and 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. ,
Figure 2 is a schematic diagram of the reverse rolling equipment, Figure 3 is a diagram showing the relationship between line speed and lead rate, Figure 4 is a diagram showing the slip detection mechanism, Figure 5 is a diagram showing the lead rate correction method, and Figure 5 is a diagram showing the lead rate correction method. FIG. 6 is a diagram showing the control characteristics of the method of the present invention, FIG. 7 is a diagram showing the control characteristics of the conventional method,
FIG. 8 is a diagram showing conventional current control, FIG. 9 is a diagram showing conventional speed control, and FIG. 10 is a diagram showing the relationship between strip speed, read rate, and current. 1... Entrance reel, 2... Strip, 3...
Back tension side deflector roll, 5...
Rolling roll, 7...Forward tension side deflector roll, 8... Output side reel.

Claims (1)

[Scope of Claims] 1 Deflector rolls are provided on the back tension side and the forward tension side of the rolling mill, respectively, for contacting the strip and detecting its moving speed, and each deflector roll is adjusted to the moving speed of the strip. In addition, in the method of rotationally driving the drive motor, there is 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 that controls the drive motor on the forward tension side based on the rotation speed of the deflector roll. A method for controlling speed detection rolls of a rolling strip, characterized in that each speed detection roll is controlled by a speed control method.