JPH0155048B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a rolling mill control device, and particularly to a speed control device for a tandem rolling mill that employs tension control between rolling mill stands and switches from tension control to droop characteristic control when roll slip occurs. The present invention relates to a rolling mill control device suitable for performing the following steps.

Generally, in rolling equipment, tension control is employed to roll the material between rolling mill stands with a certain tension. If a slip occurs between the rolling roll and the material, this tension control cannot be continued, so it is necessary to switch to drooping characteristic control. At this time, the speed correction signal is rapidly switched, but this has an adverse effect such as creating tension in the rolled material between the stands and forming a loop. When controlling the speed of such a tandem rolling mill, it is necessary to switch to drooping characteristic control without deteriorating the quality of the rolled material.

Fig. 1 is a block diagram showing the configuration of a well-known rolling mill control device that performs basic speed control of a tandem rolling mill. Electric motor, 4 is rolled material, 5
6 is a drooping characteristic control circuit, 7 is a tension control circuit that controls the tension of the rolled material 4, and 8 determines the speed of the rolling mill stand 1. 9 is a drooping amount setting device for setting the drooping amount of the drooping characteristic control circuit 6, 10 is a speed reference signal for the rolling mill stand 1, 11 is a changeover switch between tension control and drooping characteristic control, and 12 is a tension control or a speed control signal for the rolling mill stand 1 including a speed correction signal based on drooping characteristic control; 17 is a rolling current signal obtained from the current of the electric motor 3 for driving the rolling mill via an acceleration/deceleration current removal circuit 21; 20 is a rolling current signal obtained from the rolling mill drive electric motor 3; A rolling load detector detects the load and generates a rolling load signal 18, and 16 is a motor speed correction signal from the tension control circuit 7.

In a rolling mill control device having such a configuration,
The basic operations of the tension control circuit 7 and drooping characteristic control circuit 6 used to control the tension of the rolled material 4 between the rolling stands 1 and 2 are as follows. First, the tension control circuit 7 holds the rolling torque obtained from the rolling load signal 18 and the rolling current signal 17 when the rolled material 4 is being bitten by only a single stand as the rolling load and rolling torque in a non-tensioned state.

Next, the rolling load and rolling torque are also detected while the rolled material 4 is biting in tandem. At this time,
Tension is generated between the stands 1 and 2, and the tension torque ΔG _M due to this tension is expressed by the following formula.

△G _M = G _MO /P _MO ×P _M −G _M (Kg・m) …(1) Here, P _MO is the rolling load in the no-tension state, G _MO is the rolling torque in the no-tension state, P _M is the rolling load during tandem rolling, and G _M is the rolling torque during tandem rolling.

If ΔG _M =0, it means that there is no tension. Therefore, when this ΔG _M is occurring, if the speed of the electric motor 3 is corrected by ΔN _M expressed by the following formula, the tension can be controlled to the target tension.

△N _M = G _M (S) × (T _M − T _MO ) (rpm) …(2) T _M = △G _M /A _M × R _M ×i _M …(3) Here, G _M (S ) is the control gain, T _M is the current value of the tension between the stands, T _MO is the target value of the tension between the stands, A _M is the plate thickness at the exit side of the stand, R _M is the stand roll diameter, and i _M is the gear ratio.

The tension of the rolled material between the stands is controlled by adding this correction amount ΔN _M to the speed reference signal 10 from the speed reference circuit 8 to obtain a speed control signal.

FIG. 2 is a block diagram of the tension control circuit 7 used for such control, and 22 in the figure shows the rolling current signal 1.
23 is a tension torque calculation circuit which receives the rolling torque from the rolling torque calculation circuit 22 and the rolling load signal 18 from the rolling load detector 20, and 24 is calculated by the tension torque calculation circuit 23. The current value of the inter-stand tension determined by equation (3) from the current value of the tension torque and the inter-stand tension setting value from the inter-stand tension setting device 25 are input, and the motor speed correction signal 16 is calculated by equation (2). This is a speed correction signal calculation circuit that outputs .

The operation of this tension control circuit 7 is as follows. First, the rolling current signal 17 is input and the rolling torque is calculated. This rolling torque and the rolling load signal 18 detected and input by the rolling load detector 20
The tension torque is calculated from the tension torque calculation circuit 23. Next, this tension torque is divided by the plate thickness, roll diameter, and gear ratio, that is, the calculation of equation (3) is executed to obtain the current value of tension. From the difference between this current tension value and the tension setting value from the stand tension setting device 25, a speed correction amount is determined and output according to equation (2).

On the other hand, the drooping characteristic control in the drooping characteristic control circuit 6 reduces the motor speed in accordance with the rolling current obtained by removing the acceleration/deceleration current from the current of the electric motor 3 for driving the rolling stand 1, thereby reducing the speed between the stands 1 and 2. Rolled material 4
It changes, or lowers, the tension generated in the Note that this drooping characteristic control does not control the tension generated in the rolled material 4 between the stands 1 and 2, but rather controls the tension based on the equilibrium point of the motor current between the stands 1 and 2. The relationship between the rolling current and the speed correction amount is expressed by the equation below, and the coefficient K is determined from the rolling model equation.

△N _M ′=K×I _R …(4) Here, I _R is the rolling current, and K is the drooping coefficient.

By adding this correction amount △N _M ' to the speed reference signal and setting it as the speed control signal 12, the rolling mill stand 1
The tension of the rolled material 4 between the stands 1 and 2 is limited.

To explain this using FIG. 1, the drooping characteristic control circuit 6 multiplies the drooping amount setter 9 by the rolling current signal 17 and outputs this as a speed correction amount to reduce the speed between the stands 1 and 2. The tension of the rolled material 4 is limited.

Now, in the tension control of a rolling mill, if a slip occurs between the rolling roll and the rolled material 4, the rolling torque will no longer show the actual value, and the speed correction amount △N _M obtained from this rolling torque will also be inaccurate. The value becomes zero, making it impossible to continue tension control. As a result, tension control has to be discontinued, but if tension control is discontinued, abnormally excessive tension may occur in the rolled material 4 between stands 1 and 2 due to the speed difference between stands 1 and 2. , the electric motor 3 becomes overloaded and the electric motor 3 is disconnected by a protection circuit (not shown) of the Leonard device 5, making rolling impossible. Therefore, it is necessary to switch to droop characteristic control by operating the changeover switch 11. Then, as shown in the above formulas, the motor speed is reduced according to the load current of the motor for driving each stand 1 and 2 to reduce the speed difference between stands 1 and 2. It is necessary to prevent abnormally excessive tension from occurring in the rolled material 4 or to prevent the electric motor 3 from being overloaded. Note that slips are detected by passing the motor current through a bandpass filter or the like to detect current oscillations characteristic of slips, and when such current oscillations are detected, the system automatically switches to droop characteristic control. It is common that there is

However, simply switching the speed correction signal 16 when stopping tension control from the output of the tension control circuit 7 to the output of the drooping characteristic control circuit 6 causes a large difference in the values of the speed correction signals from each control circuit. , the speed control signal 12 to the electric motor 3 for driving the rolling mill changes rapidly. For this reason, an abnormally excessive tension is generated in the rolled material 4 between the stands 1 and 2, and there is a problem that the quality of the rolled material 4 is also adversely affected.

Therefore, an object of the present invention is to eliminate the above-mentioned drawbacks of the prior art, and to provide a method for smoothly switching from tension control to drooping characteristic control without causing abnormally excessive tension in the rolled material between stands or overloading the electric motor. The object of the present invention is to provide a rolling mill control device that makes it possible.

Hereinafter, the present invention will be explained in more detail with reference to the drawings. FIG. 3 is a block diagram showing the configuration of a rolling mill control device according to an embodiment of the present invention. The difference from the configuration shown in FIG. A circuit 13 is added, and the output signal 14 of the droop amount setting device 9 is turned on and off by a changeover switch 11.

In this configuration, during tension control, the speed correction signal 16 from the tension control circuit 7 is added to the speed reference signal 10 via the changeover switch 11, and this is given to the Leonard device 5 as the speed control signal 12, and the rolling mill The speed of the driving electric motor 3 is controlled.

On the other hand, during drooping characteristic control, the speed correction signal 15 from the drooping characteristic control circuit 6 is added to the speed reference signal 10 via the changeover switch 11, and this is given to the Leonard device 5 as the speed control signal 12, which is used to drive the rolling mill. The speed of electric motor 3 is controlled.

When a slip occurs between the rolling roll and the rolled material 4 during tension control, the changeover switch 11 is
The state of is reversed and the speed correction signal is switched from tension control output to drooping characteristic control. As mentioned above, this switching is generally performed automatically by detecting the motor current vibration that occurs during a slip, but it goes without saying that the switching may be performed manually by an operator. When switching like this,
In order to prevent the speed correction signal from changing suddenly, a droop setting control circuit 1 is installed on the input side of the droop characteristic control circuit 6.
3 is added. This drooping amount setting control circuit 1
3 is for making K in equation (4), that is, the drooping coefficient, a time function (K=α·t), and changing the speed correction signal 15, which is the output of the drooping characteristic control circuit 6, with the passage of time. Although not shown in the figure, the drooping amount setting control circuit 13 holds the speed correction value from the tension control circuit 7 immediately before the tension control is terminated, and uses this held value and the rolling current signal 17 as the drooping amount setting control circuit 13. The drooping coefficient is compared with the value obtained by multiplying the drooping coefficient from , and when they match, the speed correction amount is switched from the drooping characteristic control circuit 6, and the speed of the electric motor 3 for driving the rolling mill changes rapidly. is prevented.

Next, the waveforms of each signal at the time of switching from tension control to droop characteristic control are shown in the time chart of FIG. 4, and based on this, the droop amount setting control circuit 13
The operation will be explained in more detail. By the way, Fig. 4A shows the state of the changeover switch 11, Fig. 4B shows the speed correction signal 16, Fig. 4C shows the rolling current signal 17,
Figure D shows the drooping amount setting signal 1 from the drooping amount setting device 9.
4. Fig. 4E shows the input signal 2 of the drooping characteristic control circuit 6.
6. FIG. 4F shows the speed control signal 12, respectively.

The drooping amount setting control circuit 13 mainly consists of an integrating circuit, and input signal 2 of the drooping characteristic control circuit 6.
6 is converted into a time function (K=α·t). In FIG. 4, t ₀ is the switching time, t ₁ is the time when the speed correction value is switched from the tension control value to the drooping characteristic control value, and t ₂ is the time to complete the setting of the drooping coefficient. As is clear from FIG. 4, from time t ₀ to time t ₁ , the drooping characteristic control circuit 13 receives the speed correction value at the time of switching from the tension control circuit 7 and the set value 14 from the droop amount setting device 9 . The value held at time t ₀ is output as _the speed correction signal 15 until the speed correction value coincides with the speed correction value obtained by
is output to perform speed correction.

Here, if the speed correction amount between time t ₀ and t ₁ is small and is within a value such that tension fluctuation can be ignored even if the speed correction signal suddenly switches to "0", the time
It is possible to immediately switch the speed correction amount from the tension control circuit 7 to the speed correction signal of the drooping characteristic control circuit 6 at time t ₀ , and the correction amount from the tension control circuit 7 at time t ₀ is rarely held. No longer needed. The time chart at this time is shown in Figure 5. Incidentally, FIGS. 5A to 5F are signals corresponding to FIGS. 4A to 4F.

By the way, in order to prevent abnormally excessive fluctuations in tension in the rolled material 4 between the stands 1 and 2,
Basically, it is sufficient to prevent the speed of the electric motor 3 for driving the rolling mill from changing suddenly. Therefore, in addition to the method exemplified in the above embodiment, the speed correction amount itself may have a time function. .

A rolling mill control device according to another embodiment of the present invention based on this idea is shown in the block diagram of FIG. 6th
The configuration of the figure is different from that of FIG. 2 in that instead of the drooping amount setting control circuit 13 and the changeover switch 11 provided immediately before it, a speed correction amount control circuit 27 is provided, and the changeover switch 11 is provided immediately after that. be.

Here, since the configuration other than the speed correction amount control circuit 27 is the same as the well-known configuration shown in FIG. 1, the operation of the speed correction amount control circuit 27 will be explained below according to the time chart of FIG. 7. do. By the way,
FIG. 7A shows the output signal 29 of the drooping characteristic control circuit 6,
FIG. 7B shows the output signal 30 of the tension control circuit 7,
Figure C shows the output signal of the speed correction amount control circuit 27, the seventh
Figure D shows the speed correction signal 15 based on drooping characteristic control, and Figure 7 E shows the speed correction signal 16 based on tension control.
Figure F shows the speed control signal 12, respectively.

Now, the speed correction amount control circuit 27 is mainly composed of an integrating circuit, and uses the speed correction signal 15 as a function of time. In FIG. 7, _t10 is the time for switching from tension control to drooping characteristic control, and _t20 is the time to complete speed correction amount control. As is clear from the figure, the speed correction amount control circuit 27 uses the output signal 30 from the tension control circuit 7 at the time of switching as an initial value and outputs the output signal 2 from the drooping characteristic control circuit 6.
9, and this output signal 28 is output as the speed correction signal 15 via the changeover switch 11 to prevent the speed correction signal from changing rapidly.

As described above, according to the present invention, in tandem rolling, when switching from tension control to droop characteristic control, the quality of the rolled material may deteriorate due to abnormally excessive tension, and the electric motor may be damaged due to overcurrent caused by this abnormality. It is possible to obtain a new rolling mill control device that enables smooth switching without causing the inconvenience of disconnection and making rolling impossible.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of a well-known rolled material control device, FIG. 2 is a block diagram of the tension control circuit shown in FIG. 1, and FIG. 3 is a configuration of a rolling mill control device according to an embodiment of the present invention. Block diagrams showing Figures 4 and 5
The figure is a time chart of each signal in the configuration of FIG. 3, FIG. 6 is a block diagram of a rolling mill control device according to another embodiment of the present invention, and FIG. 7 is a time chart of each signal in the configuration of FIG. This is a time chart of the signal. 3...Electric motor, 5...Leonard device, 6...
Drooping characteristic control circuit, 7...Tension control circuit, 9...
Drooping amount setting device, 13...Drooping amount setting control circuit, 2
7...Speed correction amount control circuit.

Claims (1)

[Claims] 1. Tension control means for applying a first correction amount to the speed standard of the roll driving electric motor when controlling the tension of the tandem rolling mill, and applying a second correction amount to the speed standard when controlling the drooping characteristic of the tandem rolling mill. a drooping characteristic control means, and when switching the tandem rolling mill from the tension control to the drooping characteristic control,
A rolling mill control device comprising: switching means for applying a third correction amount that gradually and continuously changes from the first correction amount to the second correction amount to the speed reference.