JPH11188413A - Method of controlling continuous hot rolling mill - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve product accuracy and yield by obtaining manipulated volumes by solving plural state equations each described using state variables, input variables, and output variables for a rolling mill to be controlled, and by outputting the manipulated volumes to each control unit via specified low pass filters. SOLUTION: A state variable consists of entire set or partial set of delivery- side sheet thickness deviation, looper angle deviation, inter-stand tension deviation, inter-stand sheet speed deviation, and looper torque deviation or looper angular velocity deviation. The entire set of partial set of set values of looper torque or velocity, mill speed, and reduction position is made input variables. A state equation with the entire set or partial set of delivery-side sheet thickness, looper angle, and inter-stand tension as output variables is described, and by solving the state equation, manipulated volumes of each control unit are obtained and outputted to each control unit via a given low-pass filter 24.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling a plate thickness, a tension between stands, and a looper angle of a hot continuous rolling mill. Using a mill speed control device and a rolling position control device arranged at a position, a control method of a hot continuous rolling mill for controlling an exit side plate thickness, a tension between stands, and a looper angle to desired values, and in particular, exists in a control system. Detection noise, noise generated by rolling work roll eccentricity,
The present invention relates to a method for compensating for the influence of high-frequency vibration (chattering) or the like due to a nonlinear operation such as a sliding mode controller.

[0002]

2. Description of the Related Art A rolled work roll used in a hot continuous rolling process for manufacturing a steel sheet usually has eccentric wave noise due to eccentricity, and measurement noise by a tension measuring device is present. These noises are amplified by the controller, causing variations in plate thickness, tension, and roll speed, deteriorating control performance and reducing product accuracy. As a method for solving the problem caused by the eccentric wave noise, Japanese Patent Application Laid-Open No. Sho 54-112367 discloses that the noise of the eccentric waveform of each backup roll is removed and stored.
There is disclosed a method of controlling the eccentricity of a roll by reading out in correspondence with the rotation position of the roll during rolling.
As a method for solving the problem caused by the measurement noise, Japanese Patent Application Laid-Open No. 56-13109 discloses a method in which detection data of a rolling process is alternately integrated and stored at regular intervals using two integrators. A method has been disclosed in which a weighted average is obtained to attenuate noise in detection data to improve tension detection accuracy and control accuracy.

[0003]

However, each of the above publications is a control method applied to each control loop of a distributed control system, and is a method of directly processing and compensating a measurement signal. Cannot eliminate the effect of the excitation (spillover) caused by the spillover. In addition, there is a problem that it cannot be applied to a three-input three-output centralized controller that simultaneously operates the rolling position control device, the looper torque control device, and the mill speed control device.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and reduces the effects of noise in a control system and excitation by a controller. It is an object of the present invention to provide a method for controlling a continuous hot rolling mill.

[0005]

According to the present invention, there is provided a method for controlling a continuous hot rolling mill according to the present invention, which calculates a delivery side plate thickness, a tension between stands, and a looper angle, and controls a torque of a looper disposed between stands. Or a speed control device, using a mill speed control device and a rolling position control device arranged in each stand, in a control method of a hot continuous rolling mill that controls a delivery side plate thickness, a tension between stands, and a looper angle to desired values. The rolling mill to be controlled is a state variable consisting of a whole set or a subset of the exit side sheet thickness deviation, looper angle deviation, stand-to-stand tension deviation, stand-to-stand plate velocity deviation and looper torque deviation or looper angular velocity deviation, and the torque of the looper Complete set or subset of set value or speed set value, mill speed set value and rolling position set value as input variables, complete set of exit side plate thickness, looper angle and stand-to-stand tension Or describe the subset as a state equation and output variables by solving the state equations determine the amount of operation of each control unit, and outputs the manipulated variable to the control device via a predetermined low-pass filters.

In the present invention, a low-pass filter is provided at the front end of each of the operation amounts, for example, the gap setting value, the looper torque setting value, and the work roll speed setting value, and is included in the operation amount signal from the controller, for example. By performing control by removing high-frequency components, the influence of the above-described noise and excitation signal is reduced, and the response is less likely to be disturbed, and the response is stabilized. In the present invention, when the tension / looper / plate thickness control is performed using a centralized controller, the state predictor is incorporated in the control system, so that the state predictor exists in the operation path and the detection path of the control system. Compensate for time delays, improve product accuracy, and achieve more robust plate thickness, tension, and looper angle control effects.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 FIG. FIG. 1 is a block diagram showing a control system to which a control method according to an embodiment of the present invention is applied and related equipment, and FIG. 2 is a block diagram showing details of the control device of FIG. Normally, a hot finishing mill is composed of about seven stands, and FIG. 1 shows two stands among them. The following description is similarly applied to other stands (not shown).

1 and 2, 1 is an i-stand work roll, 2 is an i-stand backup roll, and 3 is an i-stand work roll.
+1 stand work roll, 4 is an i + 1 stand backup roll, 5 is a #i looper, 6 is a #i looper motor, 7 is an i stand mill motor, 8 is an i + 1 stand exit thickness gauge, and 9 is a stand measured by a looper roll. The inter-tension record 10 is the looper angle record. These i +
Output of thickness gauge 8 on one side of stand, actual tension between stands 9
The control operation is performed based on the information of the looper angle record 10. 11 is i + 1 stand gap record, 12
Is the i + 1 stand rolling load result, and the gauge meter plate thickness obtained by substituting these results 11 and 12 into a so-called gauge meter formula may be used instead of the i + 1 stand exit side thickness gauge 8. 13 is a #i looper motor torque record, and 14 is an i stand mill motor speed record. 15 is i + 1 stand gap setting value, 16 is #i
The looper motor torque setting value 17 is an i-stand mill motor speed setting value.
14 becomes the set value signal. Reference numeral 18 denotes a reduction APC (a reduction position control device) for controlling a gap length,
9 is a #i looper motor torque control device, and 20 is an i stand mill motor speed control device.

Reference numeral 21 denotes a control device, 22 denotes a sliding mode control controller, and 23 denotes an estimation estimator (observer) for estimating the internal state of the controlled object. The design method of the state estimator 23 is widely and generally known, such as a pole assignment designating method and a Kalman filter. Reference numeral 24 denotes a low-pass filter which is a main part of the present embodiment. These 18, 19,
Reference numerals 20 and 21 each include a computer having a storage device and an arithmetic device, which is automatically executed by a control program.

Next, the details of the control device 21 will be described based on a design policy and a design example. Usually, a model of a hot rolling system is composed of a rolling mill model, a tension model, a looper model, and a transfer model. These are modeled as linear approximation models around the operating point from the following static rolling theoretical equations and equations of motion. The variables used below are summarized.

[0011]

(Equation 1)

The deviation of the above variables from the reference value is represented by [Δ], and the basic formula of dynamics is shown below.

[0013]

(Equation 2)

However, the constants in the equation are summarized below.

[0015]

(Equation 3)

When the above dynamics are arranged, the model shown in FIG. 1 (FIG. 2) can be represented by the following differential equation.

[0017]

(Equation 4)

[0018] _{Here, a j, b j, c} j, d j, is e _j is the impact factor. The state variable vector X, the output variable vector Y, and the manipulated variable vector U are expressed by equations (15) to (17), respectively.
Then, the state equation (18) can be constructed.

[0019]

(Equation 5)

The model of equation (18) is represented by ΔT (for example, 10 m
Discretization in s) gives the state equation of the rolling system.

[0021]

(Equation 6)

Next, the low-pass filter 24 will be described. This low-pass filter 24 is installed at the input end of each operation amount. The cutoff frequency of each filter is designed based on the frequency band of the noise present in the corresponding manipulated variable. By the way, in the continuous hot rolling, the chattering of the discrete sliding mode control is due to a delay depending on the control cycle, and in consideration of the control cycle of the existing process, the chattering frequency is 50 Hz to 100 Hz.
About. On the other hand, it is known that a noise of several tens of Hz is present in the tension measurement signal, and chattering can be avoided by suppressing even the tension noise. Therefore, the cutoff frequency of the low-pass filter 24 is determined based on the tension noise. Specifically, the frequency ω _{σ of the} noise component is obtained from the measured tension data obtained by the actual operation.
And the cutoff frequency ω of the low-pass filter 24
Set _c to a lower frequency (ω _c <ω _σ ).

Each filter in the low-pass filter 24 is designed as a second-order lag system as shown in FIG. 3, and each state equation is described as follows.

[0024]

(Equation 7)

The following equations together describe these filters.

[0026]

(Equation 8)

When the above equation is discretized by ΔT (for example, 10 ms), the discrete state equation becomes as follows.

[0028]

(Equation 9)

The state equation of the expanded plant obtained by combining the equation (19) of the rolling system and the equation (24) of the low-pass filter is as follows.

[0030]

(Equation 10)

A servo system is constructed by adding an integrator to the control system. This integrator to a new variable

[0032]

[Equation 11]

The servo system is described as follows.

[0034]

(Equation 12)

Where d represents a step-like disturbance.
Rewriting the above equation gives the following:

[0036]

(Equation 13)

The state quantity of the servo system is described by equation (30).

[0038]

[Equation 14]

Next, the design of the controller 22 will be described. In the control method of the present embodiment, the expansion system (2) including the rolling process, the low-pass filter, and the integrator is used.
9) Design a controller for equation. Although the controller 22 shown in FIG. 2 may be basically designed by any of optimal control, robust control, and sliding mode control, the control method of the present invention uses chattering when using a sliding mode controller that is nonlinear robust control. Therefore, the design of the sliding mode control controller will be described below.

The design of the sliding mode controller consists of two steps. The first is to determine a constraining surface (hyperplane) of the state and obtain an equivalent control input. The second is to find a reaching law (non-linear input) for generating a sliding mode by constraining the system to a hyperplane.

Designing the Equivalent Control Input The switching function for the expanded system of equation (29) is chosen as follows.

[0042]

(Equation 15)

A control system in which the state of the system is constrained to a hyperplane is called an equivalent control system. The input at this time is a linear equivalent control input and is obtained as follows. The switching function of a system constrained to a hyperplane satisfies the following relation:

[0044]

(Equation 16)

Equations (31) and (32) are converted to the system (29)
By substituting into the equation, the following equivalent control input u _eq (k) is obtained.

[0046]

[Equation 17]

Using the equivalent control input obtained above, the system becomes the following equivalent control system.

[0048]

(Equation 18)

[0049] it is necessary to design the hyperplane matrix S _a to be stable the equivalent control system. Here, for example, a method utilizing zeros of the system is used for designing the hyperplane. That is, a method of setting the zero of the system consisting of (φ _a , Г _a , S _a ) in a unit circle on a complex plane.
Specifically, it is obtained by the following equation using the optimal control theory.

[0050]

[Equation 19]

[0051] However, P _a is a positive Teikai of the following Riccati equation.

[0052]

(Equation 20)

Φ _ε in the equation is selected as follows.

(Equation 21)

Ε is a stability margin coefficient, given by ε ≧ 0. Since the poles of the equivalent control system can be translated by this coefficient, the stability of the control system can be freely specified.

Sliding Mode Reaching Rule The reaching rule is a non-linear input for realizing σ → 0, and several methods have been proposed. Here, for example, the final SMC control method is used. This control method is
The sliding mode does not occur at all until the system state starts from an arbitrary initial value and reaches the sliding mode area S _0, and the sliding mode is generated immediately after entering the area S ₀ . In this control method,
The condition for the existence of the sliding mode is expressed by the Lyapunov function as follows.

[0056]

(Equation 22)

A reaching rule that satisfies this condition is a non-linear input based on the sign of the switching function, and is obtained as in the following u _nl (k).

[0058]

(Equation 23)

The switching gain η is a parameter for adjusting the characteristics of the reaching mode. Thus, the control law of the sliding mode servo control system is as follows.

[0060]

(Equation 24)

FIGS. 3 and 4 are diagrams showing the configuration and functions of the low-pass filter 24 of the present embodiment. The filter 24 removes high-frequency components included in the operation amount of the rolling mill. On the other hand, a control law for performing an actual control operation is as follows.
Optimal Regulator H _∞ control, it may be a sliding mode control, etc. Any control law. In particular, when a sliding mode control system designed according to the conventional nonlinear reaching rule is applied, the nonlinear operation amount is smoothed by passing through a filter, and phenomena such as chattering and spillover are prevented. Further, the output of the rolling mill may be directly detected or estimated by an observer. In any case, the influence of noise existing in the measurement signal is cut off at the input end of the operation amount, which leads to improvement in control performance.

FIGS. 5 and 6 are characteristic diagrams of an example in which the conventional method and the control method of the present embodiment are compared in response to an initial thickness deviation. In each case, the width is 0.01 kg / mm ² , 1
The control result when it is assumed that a noise of 5 Hz is generated is shown.

FIG. 5 shows the response when the above-mentioned tension noise is present in the control system and the low-pass filter is not used.
In this case, vibrations of the same frequency are generated in the tension, the delivery side plate thickness, and the operation amount corresponding to these, and it can be seen that the control performance is deteriorated.

FIG. 6 shows a low-pass filter 24 according to this embodiment.
This is the response of the control system incorporating. It can be seen that the application of the low-pass filter to the input end removes the high-frequency component of the manipulated variable caused by any cause and considerably improves the control performance of the entire control system including the controller.

[0065]

As described above, according to the present invention, the rolling mills to be controlled can be controlled so that the exit side sheet thickness deviation, looper angle deviation, stand tension deviation, stand plate velocity deviation and looper torque deviation or looper angular velocity deviation. The state variable consisting of a whole set or a subset of the set value, the total set or a subset of the torque set value or speed set value of the looper, the mill speed set value, and the rolling position set value as input variables, the outlet plate thickness, the looper angle and The whole set or a subset of the inter-stand tension is described as a state equation with an output variable, and the state equation is solved to determine the operation amount of each of the control devices, and the operation amount is controlled via a predetermined low-pass filter. Since the output is output to the device, even if a centralized controller is applied to the tension / looper / thickness control system, the effects of measurement noise and work roll eccentricity are not affected. Is Gensa, also prevents chattering due to the application of discrete sliding mode controller is, is realized better control effect, the product accuracy and improvement in yield is achieved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a control system to which a control method according to an embodiment of the present invention is applied and related equipment.

FIG. 2 is a block diagram showing details of a control device of FIG. 1;

FIG. 3 is a configuration diagram of a low-pass filter of the present embodiment.

FIG. 4 is a block diagram illustrating functions of a low-pass filter according to the present embodiment.

FIG. 5 is a characteristic diagram of an example in which responses are compared with respect to an initial thickness deviation in a conventional method.

FIG. 6 is a characteristic diagram of an example in which a comparison is made in response to an initial thickness deviation in the present embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 i stand work roll 2 i stand backup roll 3 i + 1 stand work roll 4 i + 1 stand backup roll 5 #i looper 6 #i looper motor 7 i stand mill motor 8 i + 1 stand out side thickness gauge 9 stand tension result 10 looper angle result 11 i + 1 stand gap result 12 i + 1 stand rolling load result 13 #i looper motor torque result 14 i stand mill motor speed result 15 i + 1 stand gap set value 16 #i looper motor torque set value 17 i stand mill motor speed set value 18 i + 1 stand Reduction APC (Reduction position control device) 19 #i Looper motor torque control device 20 i Stand mill motor speed control device 21 Control device 22 Sliding mode control controller 23 State estimation Vessel (observer) 24 low-pass filter

Continued on the front page (72) Inventor Kenzo Nonami 1-33 Yayoicho, Inage-ku, Chiba-shi, Chiba

Claims (1)

[Claims] 1. An outlet side plate thickness, a stand-to-stand tension and a looper angle are determined, and a torque control device or a speed control device of a looper disposed between stands, a mill speed control device disposed on each stand, and a rolling position. In a control method of a hot continuous rolling mill for controlling a delivery thickness, a tension between stands, and a looper angle to desired values using a control device, a rolling mill to be controlled is provided with a delivery thickness deviation, a looper angle deviation, A state variable consisting of the entire set or a subset of the stand-to-stand tension deviation, stand-to-stand plate velocity deviation and looper torque deviation or looper angular velocity deviation, and the looper torque set value or speed set value, mill speed set value, and rolling position set value Describe as a state equation the whole set or a subset as an input variable, and the whole set or a subset of the exit plate thickness, looper angle, and stand-to-stand tension as an output variable. By solving the state equations determine the amount of operation of the respective control device, the hot method of controlling the continuous rolling mill and outputs the operation amount to said each control device via a predetermined low-pass filters.