JP3041155B2 - Looper control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a looper control device for simultaneously controlling the height of a looper disposed between stands of a tandem hot rolling mill and the tension between stands of a rolled material.

[0002]

2. Description of the Related Art One of the evaluation criteria of a final product in hot rolling or cold rolling is a sheet thickness and a sheet width. Since the sheet thickness and the sheet width are affected by the tension applied to the material during rolling, control is performed to keep the tension at a certain value.

[0003] In particular, since the rolled material in hot rolling is heated to a high temperature due to heat treatment and the deformation resistance of the rolled material is reduced, the material is easily broken when a large tension is applied. If the tension is set low to prevent this breakage, there may be no tension due to disturbance or erroneous setting, and if that condition continues, a large loop will occur between the rolling mill stands and an accident will occur. Maybe. Therefore, in the hot rolling mill, a looper device is particularly provided between the stands, and the tension control is performed by the looper device, and the height of the looper is simultaneously controlled from the viewpoint of improving the material passing property.

However, in the control device for controlling the rolled material tension and the looper height, interference occurs from the rolled material tension to the looper height, and interference occurs from the looper rotation speed to the tension. In the conventional looper control, a method of controlling the rolled material tension and the looper height by PID (proportional-integral-derivative operation) control without providing any means for suppressing such interference (hereinafter, referred to as “individual control method”). Has been taken.

On the other hand, the interference system described above is treated as a multivariable system, and a non-interference compensation device for suppressing the interference is added to control the tension of the rolled material and the height of the looper independently of each other. Or an optimal control that applies an optimal control theory (LQ) to coordinately control the rolled material tension and the looper height, and an ILQ (an inverse LQ) that solves the inverse problem of the LQ and obtains the control gain by a mathematical expression. Multivariable control, such as H∞ control, which can take into account the robustness of control and control systems, is known, and each is applied to an actual machine.
Here, the robustness means that noise is added to the control system,
It is a property that is less likely to be unstable even if the control target changes.

[0006]

The above-described multivariable control includes:
It is premised to detect the rolled material tension and the looper angle in order to make use of each feature, and therefore, it is difficult to apply the method to a rolling mill without a tensiometer. Also, the i-th stand (i-th stand from the upstream side) of the rolling mill and the i-th stand
The tension between the + 1st stands is generated after the leading end of the rolled material is bitten by the (i + 1) th stand, that is, after the (i + 1) th stand passing plate. During this pass, the disturbance is very large,
Until a while after passing the i + 1st stand, the tension detection value obtained by the tension meter becomes unstable, and during this time, the tension detection value required for multivariable control cannot be obtained. Therefore, an individual control method that does not require a tension meter is required. It becomes.

Further, depending on the rolling material, the tension control by the multivariable control cannot completely cover the rolled material, and a well-adjusted individual control method may show a better control performance in some cases. It is necessary to do it.

As described above, the conventional individual control method does not have the function of suppressing the mutual interference between the tension of the rolled material and the height of the looper, and thus may be inferior to multivariable control in terms of quick response and stability. This is because the control response of the looper height control cannot be sufficiently increased for the following reason.

When the tension and the looper system are represented by transfer functions, 2
The following resonance system is included. The characteristic of the secondary resonance system is
Represented by the resonance frequency omega _n and damping factor zeta, the looper crossover angular frequency of the high control response approaches the resonance frequency omega _n,
Resonance occurs near this frequency, and when the damping constant ζ is small, it becomes oscillating. Therefore looper response height control is limited to less than about 1/4 of the resonance frequency omega _n, must be kept even lower depending on the value Ikan the attenuation constant zeta.

On the other hand, conventionally, there is a method of increasing the looper damping equivalently by multiplying the looper rotation speed by a certain constant and converting the converted value into a reference value of the current and adding the converted value to the looper current reference value. . However, in this method, the response of the looper motor becomes slow, which adversely affects the tension control of the rolled material.

The present invention solves the above problems based on the individual control method described above, without the necessity of a tension meter, and eliminating the mutual interference between the tension control and the looper height control.
It is an object of the present invention to provide a looper control device capable of performing highly accurate and stable looper control.

[0012]

SUMMARY OF THE INVENTION According to the present invention, a main machine speed command value is calculated so that the height of a looper disposed between stands of a tandem hot rolling mill matches a looper height target value.
Looper height control means for driving and controlling the looper electric motor via the main machine speed control means according to the main machine speed command value, and a tension target value and a looper height based on the tension target value and the roll material height to make the rolled material tension between the stands coincide with the tension target value. A looper control device that calculates a looper current command value and controls a looper electric motor through a looper current control device in accordance with the looper current command value, the looper control device changing a resonance frequency of the looper control system. Frequency change means for calculating a first main engine speed change amount command value for changing the damper constant of the looper control system so as to compensate for the change of the damping constant due to the change of the resonance frequency in the looper control system. Second
Damping constant changing means for calculating the main engine speed change amount command value, and adding the first main machine speed change amount command value and the second main machine speed change amount command value to the main engine speed command value to obtain a new main machine speed command value. Means for inputting to the main engine speed control means.

[0013]

According to the present invention, the resonance frequency changing means calculates a main engine speed change amount command value for changing the resonance frequency of the looper control system, and the damping constant changing means compensates for the fluctuation of the damping constant due to the change of the resonance frequency. To change the damping constant of the looper control system so that the main engine speed command value is corrected by the two main machine speed change command values. Input to the control unit. By doing this,
The control response of the looper control system can be increased, and high-precision and stable looper control can be performed.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in more detail with reference to embodiments shown in the drawings. (First Embodiment) FIG. 1 is a block diagram showing one embodiment of the present invention. In FIG. 1, a rolled material 1 is rolled in the order of a rolling mill of an i-th stand counted from an upstream side, that is, an i-th stand rolling mill 2 and a subsequent i + 1-th stand rolling mill 3. Here, the total number of stands of the tandem rolling mill is n
Then, n = 5 to 7 is general. The devices such as the looper shown below are installed between each adjacent stand. If the behavior between two specific adjacent stands is considered, the result of the consideration can be easily extended to the behavior between other stands. Therefore, only the behavior between the i-th stand and the (i + 1) -th stand will be considered here. Note that i
Is 1 ≦ i ≦ n−1.

A looper 4 is provided between the i-th stand rolling mill 2 and the (i + 1) -th stand rolling mill 3. Looper 4
Is detected by the looper height detector 5. The looper height detected by the looper height detector 5 is converted into the angle of the arm of the looper 4, that is, the angle of the looper arm. The looper motor 6 for driving the looper 4 is provided looper current detector 9, it is fed back the detected value I _L to the looper current control means (CC) 8. Looper current control unit 8 controls the operation so as to follow the detected value I _L to the current command value I _LREF which is set by the looper tension control means (LTC) 10. Also,
The speed detector 7 is attached to the looper motor 6, and the detection signal is sent to the resonance frequency changing means 15 and the damping constant changing means 16 described later.

The looper tension control means 10 calculates a current command value I _LREF such that the actual rolling material tension between the two rolling stands follows the tension command value t _fREF (kg / mm ² ). F _o ^* (θ, t _fREF ) = g [(R ₁ / g _L ) t _fREF A {sin (θ + β) −sin (θ−α)} + (R ₂ / g _L ) W _S cos θ + (R ₃ / g _L ) W _L cos θ] × 10 ⁻³ (1) where, I _LREF = F _o ^* (θ, t _fREF ) (2) where θ: looper angle (rad) g: gravity Acceleration (mm / s ² ) = 9.8 R ₁ : Distance from looper rotation center to looper roll center (mm) R ₂ : Looper roll radius (mm) R ₃ : Distance from looper rotation center to looper center of gravity (mm) g _L : Gear ratio between looper machine and looper motor A: Cross-sectional area of rolled material (mm ² ) (product of plate thickness and plate width) α: Angle between pass line and rolled material at exit side of i-th stand ( rad) beta: determined from the mass of the strip between the stands (kg) (cross-sectional area of the rolled material, length, and density: the (i + 1) stand angle of the incoming side in the pass line and rolled material (rad) W _S ) W _L: looper Weight (kg) (1), equation (2), looper angle θ and the tension command value t
_{When fREF} is set, the current command value I _LREF can be calculated.

[0017] On the other hand, the i stands of the rolling mill traction motor (hereinafter, rolling mill main electric motor of main engine) speed V _M of 11 is controlled by the main engine speed control means (ASR) 13. The main motor speed control means 13, the main engine speed detector 12 main engine speed detection value V _M detected by (a rate converted to have the same dimensions and roll peripheral speed V _R to be described later) in the speed command value V _MREF The current control of the i-th stand main machine 11 is performed so as to follow.

The main-machine speed change amount command value ΔV _RREF is controlled by a looper height control means so that the looper angle θ corresponding to the looper height detected by the looper height detector 5 follows the looper height target value θ _REF. LHC) 14 computes it, algebraically adds it to the initial main engine speed command value, and sets the new main engine speed command value in main engine speed control means 13.

The resonance frequency change means 15 inputs the looper motor speed omega _L detected by the looper motor speed detector 7, a first main machine speed change amount command value so as to change the resonant frequency of the looper control system [Delta] V _R1 Similarly, the damping constant changing means 16 similarly receives the looper motor speed ω _L and calculates a second main engine speed change amount command value ΔV _R2 for changing the damping constant of the looper control system. Algebraically added to the initial main engine speed command value together with the change amount command value ΔV _RREF to obtain a new main engine speed command value as the main engine speed control means 13
Set to.

Next, a method of changing the resonance frequency and the attenuation constant will be described.

FIG. 2 is a control block diagram describing an example of the individual control method of the looper. The control target of the looper height control is a portion surrounded by a broken line.

[0022] in a non-linear relationship between the general looper angle to be controlled in θ and the main engine speed V _M which is an operation amount. Therefore, the looper angle theta, then converted to the rolled material loop amount L _P between the stand in the relation of the main engine speed V _M and linear, the loop amount L _P
Is used to configure a looper height control system. The non-linear function F ₂ ^* (θ) for converting the looper angle θ into the loop amount L _P is represented by equation (3). F ₂ ^* (θ) = {(L ₁ + R ₁ cos θ) / cos α} − {(L−L ₁ −R ₁ cos θ) / cos β} −L (3) The loop amount L _P is L _P = F ₂ ^* (θ) (4) where L: distance between stands (mm) L ₁ : distance from the center of rotation of the looper to the i-th stand (mm) Block according to equations (3) and (4) 17 converts the looper angle target value theta _REF loop amount target value L _PREF, block 18 converts the looper angle theta to the loop amount L _P.

The loop amount L _P and the looper height control means so that difference or loop amount deviation between the loop amount target value L _PREF reduced (LHC) 14 is for calculating a roll peripheral speed change amount [Delta] V _RREF. The looper height control means 14 is of a PI control type and is represented by control gains T ₁ and T ₂ .

The roll peripheral speed change amount ΔV _RREF is input to the main engine speed control system 19. The main engine speed control system 19 expresses the speed response of the main engine using a first-order lag time constant T _V (S).
Then, from the roll peripheral speed change amount ΔV _RREF , the roll peripheral speed change amount Δ
It is represented as a transfer function of a V _R. This is Figure 1
Corresponds to a portion composed of blocks 11, 12, and 13.

The roll peripheral velocity variation [Delta] V _R by the block 20 when the forward slip is f material velocity ΔV _S (mm / s)
And passes through the integrator represented by the block 21 to become a loop amount change ΔL _PV (mm) depending on the material speed. The sum of the loop amount change ΔL _PV and the loop amount change ΔL _PL due to the looper passes through the block 22 and contributes to the tension change Δt _f . E in the block 22 is the Young's modulus of the rolled material. Further, representative of the tension feedback coefficient K ₁₀ for representing the variation of the material speed of variation in tension as a block 23.

The change in the tension t _f is caused by the change in the tension torque T _T applied to the looper motor 6, that is, the change in the tension torque ΔT.
Appears as _T. The block 25 is for expressing this linearly, and the function F ₃ (θ) therefor is represented by the equation (5). F ₃ (θ) = d ｛F ₃ ^* (θ)｝ / d θ (5) where F ₃ ^* (θ) = g (R ₁ / g _L ) A ｛sin (θ + β) −sin (θ− α)｝ × 10 ⁻³ (6) The next block 26 is to calculate the rotation speed change Δω _L of the looper motor from the change ΔT _{T of the} torque applied to the looper motor 6.
And J _L is the moment of inertia of the looper. The rotation speed change Δω _L is represented in a block 29 in order to cause a looper angle change Δθ. Also,
In block 27, Z is looper damping, and block 28 is torque change Δ of looper motor 6 from looper angle change Δθ.
Shows a transfer function F ₁ (θ) up to T _T ,
It is expressed by equation (7). _{F 1 (θ) = d {} F 1 * (θ)} / dθ ... (7) ^{_{where, F 1 * (θ) =}} g [(R 1 / g L) W S cos θ + (R 3 / g _L ) W _L cos θ] × 10 ⁻³ (8) The transfer function from the looper angle change Δθ to the loop amount change ΔL _PL is block 24, and is represented by equation (9). F ₂ (θ) = d {F ₂ ^* (θ)} / dθ (9) where F ₂ ^* (θ) is based on the equation (3).

The looper tension control means 10 is expressed by F _o (θ, t _fREF ) / Φ in a linear expression. Here, Φ is a torque constant (N · m / A), and F _o (θ, t
_fREF ) is expressed by equation (10). F _o (θ, t _fREF ) = dF _o ^* (θ, t _fREF ) / dθ (10) where F _o ^* (θ, t _fREF ) is based on equation (1).

The looper current control means 8 is of a PI operation type and is expressed using control gains T _1C and T _2C .
Block 32 represents the thyristor gain K _SCR and block 33 represents the looper motor armature. Where _Ra
Represents the armature resistance, T _a is the armature conductance, respectively. Block 30 represents an influence coefficient when a change in the looper current is converted into a torque change. Since both have the same value, they are represented by the same reference Φ.

The portions represented by blocks 8, 32, and 33 in FIG. 2 are the looper motor 6, the looper current control means 8,
And looper current detector 9, and block 2 in FIG.
6, block 27, block 30, and block 31
It corresponds to the portion represented by.

In the individual control system shown in FIG. 2, when the transfer function from the roll peripheral speed change amount ΔV _RREF to the looper angle change Δθ is represented by the transfer function G (S) of the secondary resonance system
including. G (S) = ω _n ² / (S ² + 2ζ · ω _n · S + ω _n ² ) (11) where, resonance frequency ω _n = [(E / LJ _L ) ｛F ₂ (θ) · F ₃ ( θ) + K ₁₀ Z｝] _1/2 (rad / s) (12) Attenuation constant ζ = 1 / (2ω _n ) [(K ₁₀ E / L) + (Z / J _L )] (13) ( In equation (12), it can be seen that the resonance frequency can be changed if at least one of the parameters E, L, J _L , F ₂ , F ₃ , K ₁₀ and Z on the right side can be changed. However, as shown below, these parameters except F ₂ and Z are indirectly changeable are those with a unique value to the control system of the looper can not change their values directly.

FIG. 3 shows a means for equivalently changing F ₂ (θ) in the right side of the equation (12). Block 3 in FIG.
4 is obtained by simply changing the sign of block 20 in FIG. 2, and blocks 35 and 36 are blocks 21 and 22 in FIG.
2, 24 are equivalently converted. Block 37 is a collective representation of blocks 10 and 30 in FIG. 1, and block 38 is block 8 and 30 in FIG.
The looper current control system represented by 31, 32, 33 is expressed using a first-order lag time constant T _CC .

K ₁ in block 39 of FIG. 3 is a function F of block 36 having a value specific to the looper control system.
₂ (θ) in parallel with the constant control gain, and by inserting this gain K ₁ , the function F ₂ (θ) can be equivalently changed.

Here, the resonance frequency changes as follows. Resonance frequency ω _n = [(E / LJ _L ) ｛(F ₂ (θ) + K ₁ ) · F ₃ (θ) + K ₁₀ Z｝] ^1/2 (rad / s) (14) On the other hand, FIG. As a method of indirectly changing the looper damping Z shown in the block 27, the correction coefficient τ of the block 40 is added in parallel with Z. However, since the torque cannot be directly changed in practice, τ · Δω _L A method of equivalently increasing the damping of the looper by converting the reference value into a changed value and adding the converted value to the looper current reference value has been adopted. However, this method is not preferable because the response of the looper motor becomes slow and adversely affects the tension control of the rolled material.

Although it is effective to change the function F ₂ (θ) equivalently as described above for changing the resonance frequency, it is impossible to directly change the material velocity V _S. changing the material velocity V _S through a roll peripheral speed V _R.

The resonance frequency changing means 15 in FIG.
Block 39 in FIG. 3 has a similar function,
In addition, the control is changed so that the control can be realized more practically. The function K ₁ ^* of block 15 in FIG. 4 and FIG.
Relationship between the function K ₁ of block 39 in the ignoring transient response is expressed by equation (15). K ₁ ^* = K ₁ / (1 + f) (15) Here, f is the advance rate, and the exact value is not known, so the function K ₁ ^* is a value to be adjusted in the actual rolling mill.

[0036] Now, generally the larger the resonant frequency omega _n is, it is possible to increase the response of the looper height control system, desirable. However, (13) zeta attenuation constant and to increase the resonance frequency omega _n becomes smaller from equation looper height control system becomes oscillatory. Therefore, the resonance frequency ω _n
Is increased, the stability of looper control is increased by taking measures to increase the damping constant ζ accordingly. Therefore, the damping constant changing means 1 shown in FIG.
A specific example in which No. 6 is configured according to the above concept will be described below.

As one method of increasing the damping constant ζ, there is a method disclosed in Japanese Patent Publication No. 3-10406, entitled “Control Device for Electric Looper”. As shown in blocks 41 and 42 of FIG. 4, the looper rotation speed Δω _L is differentiated by a block 41 and multiplied by a constant K ₂ in a block 42. With this method, the damping constant ζ can be substantially increased.

FIG. 5 shows the resonance constant changing means 15 in FIG.
When the output of the damping constant changing means 16 is neither, that is, ΔV _R1 = 0 and ΔV _R2 = 0, the looper angle Δθ is calculated from the main engine speed changing amount ΔV _{RREF of} FIG.
FIG. This corresponds to the case where K ₁ ^* = 0 and K ₂ = 0 in FIG. FIG. 3A shows a gain diagram, and FIG. 3B shows a phase diagram. According to this, the resonance frequency is about 4 rad /
s, and the response of the looper height control is also 1/4 of 4 rad / s.
It can be seen that it is kept below the level.

FIG. 6 shows the resonance frequency changing means 1 in FIG.
Utilizing the output [Delta] V _R1 of 5, and the damping constant change unit 16
No output, that is, when ΔV _R2 = 0,
FIG. 3 shows a frequency response from the main engine speed change amount ΔV _RREF to the looper angle Δθ in FIG. 2. This corresponds to the case where K ₁ ^* > 0 and K ₂ = 0 in FIG. FIG.
(A) shows a gain diagram, and (b) shows a phase diagram. According to FIG. 6, the resonance frequency is about 8 rad / s, which is higher than in FIG. Therefore, the response of the looper height control can be made faster than in the case of FIG. However, the frequency is 8 rad / s
The peak protrusion amount in the vicinity is slightly larger than the protrusion amount in FIG.

FIG. 7 shows the resonance frequency changing means 1 in FIG.
Utilizing the output [Delta] V _R1 of 5, and the damping constant change unit 16
2 shows the frequency response from the main engine speed change amount ΔV _RREF to the looper angle Δθ in FIG. 2 when the output ΔV _R2 of FIG. This is shown in FIG. 4 where K ₁ ^* > 0, K
_This corresponds to the case where ₂ > 0. FIG. 7A shows a gain diagram, and FIG. 7B shows a phase diagram. FIG.
According to the figure, the resonance frequency is about 8 rad / s, which is not different from the case of FIG.
The peak protrusion near s is almost eliminated, making it difficult to vibrate. (Second Embodiment) As a method for increasing the damping constant, a method disclosed in Japanese Patent Publication No. 3-10406 has been described. In this method, as shown in a block 41 of FIG. Use values. However, in practice, it is difficult to achieve perfect differentiation, and the block 41 is often performed by incomplete differentiation as in equation (16). S / (1 + T _D · S) (16) Since the expression (16) is an approximation of the original differentiation, there is an influence of the accuracy deterioration, and the result is that the noise included in the actual measurement value is increased. It may not be desirable to use differentiation.

[0041] Therefore, as another way to change the damping constant, as shown in FIG. 8, damping torque estimated by Rupatoruku estimating means 43 based on the looper motor current I _L is detected by the looper current detector 9 constant The same effect as described above can be obtained by inputting the data to the changing means 16.

FIG. 9 is a diagram expressing the functional block diagram of FIG. 8 in the form of a transfer function, and multiplies the looper torque change ΔT _LP by K ₂ / J _L represented by the block 44 to obtain a main engine speed change amount command value. and calculates the ΔV _R2. Block 44 is another means for realizing the damping constant changing means 16 of FIG.

[0043] Estimation of Rupatoruku T _LP in Rupatoruku estimating means 43 in FIG. 8 is performed as follows using the looper motor current I _L and the torque constant [Phi. T _LP = Φ · I _L (17) The change amount ΔT _LP of the looper torque is calculated from the torque _TL applied from the looper motor 6 to the looper 4, the torque T _T by the tension corresponding to the tension target value, and the stand inter-plate weight. It is determined by subtracting the torque T _M by the torque T _W, and the looper of its own weight by. ΔT _LP = T _L − (T _T + T _W + T _M ) (18) T _T = F ₃ ^* (θ _REF , t _fREF ) / Φ (19) where F ₃ ^* is obtained by the equation (5). T _W + T _M = F ₁ ^* (θ _REF ) / Φ (20) where F ₁ ^* is obtained by the equation (8).

In FIG. 9, K ₁ ^* = 0, K ₂ > 0 (K
FIG. 10 shows the frequency response from the main engine speed change amount ΔV _RREF to the looper angle Δθ in FIG. 9 for the case where ( ₂ is the same value as K ₂ in FIG. 7). FIG. 10A is a gain diagram,
(B) is a phase diagram. Which in FIG. 5, K _2>
0, that is, the case where only the output of the attenuation constant changing means 16 is utilized. Since the attenuation constant is larger than that in FIG. 5, the peak protrusion amount near the frequency of 8 rad / s is almost eliminated, and it can be seen that the vibration is hardly caused. Third Embodiment On the other hand, when an accelerometer is provided for a looper machine or a looper motor, an acceleration signal obtained by the accelerometer can be used. When an acceleration signal representing the acceleration of the looper motor is obtained, the acceleration signal of the looper motor is used instead of the output of the block 41 as the input signal of the block 42 in FIG. In this case, in FIG. 4, instead of the output of the block 41, a signal obtained by multiplying the acceleration signal of the looper machine by the looper gear ratio may be used as the input signal of the block 42.

Although the present invention has been described with reference to the three embodiments, the means for realizing the attenuation constant changing means may be appropriately selected from the three methods depending on the type of the detector installed in the looper device and its accuracy. It is possible. For example, what kind of accelerometer or speedometer is provided, or when the detection accuracy of the accelerometer is poor, a value obtained by differentiating the speed detection value can be used as the acceleration value.

Although the above embodiment has been described by exemplifying a quadruple rolling mill, the present invention can be applied to a different rolling mill.

[0047]

According to the present invention, when the control of the looper height and the tension in the hot rolling is performed without providing any special interference control means, the resonance frequency and the damping constant are changed to control the looper control system. Control response can be increased, and high-precision and stable looper control can be realized.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an overall configuration of a looper control device according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating a configuration of a looper control system by a transfer function in order to explain an operation when tension control and looper control are performed under control without interference suppression measures.

FIG. 3 is a diagram showing a configuration of a looper control system by a transfer function in order to show a principle of changing a resonance frequency.

FIG. 4 is a block diagram showing a detailed configuration of the looper control device according to the first embodiment of the present invention.

FIG. 5 is a diagram showing a frequency response from a change in the main engine speed to a change in the looper angle in order to explain an operation without an interference suppression measure.

FIG. 6 is a diagram showing a frequency response from a main engine speed change amount to a looper angle change for explaining the operation of the first embodiment;

FIG. 7 is a diagram showing a frequency response from a change in the main engine speed to a change in the looper angle for explaining the operation of the first embodiment;

FIG. 8 is a block diagram showing an overall configuration of a looper control device according to a second embodiment of the present invention.

FIG. 9 is a block diagram showing a detailed configuration of a looper control device according to a second embodiment.

FIG. 10 is a diagram showing a frequency response from a change in the main engine speed to a change in the looper angle for explaining the operation of the second embodiment;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Rolled material 2 i-th stand rolling machine 3 i + 1st stand rolling machine 4 looper 5 looper height detector 6 looper motor 7 rotation speed detector 8 looper motor current control means 9 looper motor current detector 10 looper tension control means 11th i stand main unit 12 main unit speed detection unit 13 main unit speed control unit 14 looper height control unit 15 resonance frequency changing unit 16 damping constant changing unit

Claims (1)

(57) [Claims] A main machine speed command value is calculated so that a height of a looper disposed between stands of a tandem hot rolling mill coincides with a looper height target value, and main machine speed control means is operated in accordance with the main machine speed command value. A looper height control means for driving and controlling a looper motor through the looper, and a looper current command value based on the tension target value and the looper height so as to make the rolled material tension between the stands equal to the tension target value. A looper tension control means for driving and controlling a looper motor via a looper current control means in accordance with a command value, wherein a first main engine speed change amount command for changing a resonance frequency of the looper control system is provided. Resonance frequency changing means for calculating a value, and changing the damping constant of the looper control system so as to compensate for fluctuation of the damping constant caused by changing the resonance frequency in the looper control system. Damping constant changing means for calculating a second main engine speed change amount command value for correcting the main engine speed command value with the first main engine speed change amount command value and the second main engine speed change amount command value. Means for inputting a speed command value to the main engine speed control means.