WO2013183135A1

WO2013183135A1 - Method for controlling in-mold molten steel surface level

Info

Publication number: WO2013183135A1
Application number: PCT/JP2012/064620
Authority: WO
Inventors: 浅野　一哉; 島本　拓幸
Original assignee: Ｊｆｅスチール株式会社
Priority date: 2012-06-07
Filing date: 2012-06-07
Publication date: 2013-12-12
Also published as: KR20150013241A; KR101664171B1; IN2014DN10256A; CN104334298B; CN104334298A

Abstract

The objective of the present invention is to achieve high-precision control of the level of molten steel surface, by using one level gauge to extract and remove a primary, a secondary, and a tertiary standing wave component, and thus to extract only the variation in the bulging molten steel surface, which variation is to be controlled, and to use this in controlling the level of the molten steel surface. In this method, models (12, 14) are expressed with secondary vibration systems, with these models being models of the variation in the molten steel surface level due to standing waves that oscillate with a specific cycle corresponding to the mold width. In addition, the deviation between a measured level value measured with a surface level gauge and the output from the models (12, 14), and/or the differential value thereof, is fed back as an input to the models (12, 14), thereby exciting the models (12, 14), and the surface level variation component due to the standing waves is estimated by means of the obtained output from the models (12, 14), and the standing wave component is removed using the deviation between the measured level value measured with the surface level gauge and the output from the models (12, 14), thereby producing a level signal. In addition, an actuator that adjusts the flow volume of the molten steel flowing into the mold is operated by means of feedback control using this level signal.

Description

Molten steel surface level control method in mold

The present invention relates to a molten steel surface level control method in a mold of a continuous casting machine.

In a continuous casting machine, controlling the molten metal level in molten metal (molten steel) to keep the molten metal level constant and controlling the molten metal level to be constant is not only stable, but also the quality of the slab. It is extremely important for management.

Normally, the molten steel level in the mold is controlled by measuring the molten steel level in the mold using a molten metal level meter, and adjusting the opening of the sliding nozzle as a molten steel flow control device based on the measured value. And the method of balancing the mass balance of the molten steel drawn out from a mold and the molten steel poured from a tundish is taken.

Fig. 8 shows a typical example of the mold peripheral part and the surface level control system of a slab continuous casting machine. A tundish 2 is disposed at a predetermined position above the mold 1 of the slab continuous casting machine, and a sliding nozzle 3 and an immersion nozzle 4 are disposed at the bottom of the tundish 2. Thereby, the molten steel 5 once retained in the tundish 2 is injected into the mold 1 through the sliding nozzle 3 and the immersion nozzle 4. The sliding nozzle 3 is composed of a fixed plate and a sliding plate. By operating the position of the sliding plate with an actuator 6 such as a hydraulic servo system, the opening degree of the sliding nozzle 3 increases or decreases, and flows into the mold 1 from the tundish 2. The flow rate of the molten steel 5 is controlled. On the other hand, a molten metal level meter (for example, eddy current sensor) 7 is disposed above the molten steel surface in the mold 1. The molten metal level meter 7 is a device for measuring the level (height position) of the molten steel surface in the mold 1, and the measurement signal (melt level signal) of the molten metal level meter 7 is input to the molten metal level control device 8. ing.

The molten steel 5 injected into the tundish 2 from the ladle (not shown) is injected into the mold 1 through the immersion nozzle 4 according to the opening degree of the sliding nozzle 3. The injected molten steel 5 is cooled by the mold 1 and solidifies at the contact surface with the mold 1 to form a solidified shell, and the slab having the liquid phase portion inside is supported by the guide roll and the pinch roll 9 while being pinched. The roll 9 is pulled out below the mold 1. At that time, the hot water level control device 8 performs an operation such as PI control or PID control on a deviation between the hot water level signal obtained from the hot water level meter 7 and a preset hot water level setting value. The amount of operation of the sliding nozzle opening is obtained and output to the actuator 6 to adjust the flow rate of the molten steel flowing into the mold 1 from the tundish 2 by operating the sliding nozzle opening.

As a result, a feedback loop relating to the molten metal level of the molten steel 5 in the mold 1 is formed, so even if the flow rate of the molten steel 5 flowing into the mold 1 or the flow rate of the molten steel 5 flowing out of the mold 1 varies due to some factor. The molten steel surface level of the molten steel 5 in the mold 1 can be controlled to be a constant value (set value).

As a major issue in controlling the level of molten steel in the mold, it has flowed out of the mold due to bulging in the thickness direction of the slab that occurs between slab support rolls such as guide rolls and pinch rolls. There is a molten metal level fluctuation (bulging level level fluctuation) due to a periodic fluctuation of the molten steel flow rate.

What should be suppressed by the molten steel surface level control in the mold is the fluctuation of the molten metal surface level due to disturbance that causes substantial mass flow fluctuations such as bulging as described above. The fluctuation acts as measurement noise in the molten metal level control, and the sliding nozzle opening operation should not be performed in response to the fluctuation.

Especially when the mold width is increased, a standing wave in which the molten metal surface fluctuates at a natural frequency corresponding to the mold width becomes a problem. Of particular concern is a primary standing wave having one vibration node as shown in FIG. 9 (a), the node being at the mold width center (mold width 1/2 position), As shown in FIG. 9B, there are two vibration nodes, and the node is a secondary standing wave in the middle of the mold width center and the mold width end (mold width 1/4 position). In particular, as the mold width increases, the vibration frequency decreases (when the width is 2 m, the frequency of the primary mode is approximately 0.6 Hz), which approaches the bulging frequency (0.1 to 0.2 Hz).

Generally, in the feedback control system, it is necessary to suppress the influence of the disturbance by increasing the gain at the frequency of the disturbance to be removed and not to react to the measurement noise by decreasing the gain at the frequency of the measurement noise. That is, it is necessary to design the frequency characteristics of the feedback control system in consideration of disturbance and measurement noise. However, in this case, since the fluctuation level of the molten metal level due to the disturbance to be originally removed is close to the frequency of the molten metal level fluctuation caused by the measurement noise, the control parameters (PI control gain, etc.) of the molten metal level control device 8 Adjustment becomes difficult. That is, when the gain is increased, the hot water level control device 8 picks up measurement noise and outputs an unnecessary sliding nozzle opening manipulated variable, whereby the hot water surface level fluctuates, and the level meter 7 measures it. Therefore, a loop of outputting to the hot water surface level control device 8 occurs. As a result, the fluctuation of the molten metal surface level may be increased or, in an extreme case, the control system may diverge without being stabilized. On the other hand, when the gain of the molten metal level control device 8 is lowered, the control performance with respect to the bulging molten metal surface fluctuation is deteriorated, and the cyclic molten metal surface fluctuation cannot be reduced.

Therefore, as a method for improving the control performance against fluctuations in the bulging level, in Patent Document 1, frequency analysis is performed on the level signal from the level gauge, and when the frequency of the bulging is detected, only the vicinity of the frequency is detected. The method of performing the hot water surface level control based on the differential value of the component is described. However, in this method, since the above-described standing wave is not considered to be processed as measurement noise, the influence of the standing wave cannot be removed.

In order to deal with such a problem, in Patent Document 2, the standing wave frequency corresponding to the standing wave fluctuation of the molten metal surface level fluctuation is calculated from the mold width, and the standing wave is described by a sin function and a cos function of the frequency. In addition, a method for detecting a standing wave fluctuation in a mold in which a standing wave fluctuation is obtained by estimating these coefficients online is disclosed.

Moreover, in patent document 3, the hot_water | molten_metal surface level from which the primary standing wave component was removed is measured by installing the hot_water | molten_metal surface level meter in the center position of a mold, and it uses frequency filter and 2 In the mold of a continuous casting machine, a corrected molten metal level signal from which the frequency component of the standing wave has been removed is obtained, and the opening of the sliding nozzle is adjusted so that the obtained corrected molten metal level signal is constant. A molten steel level control method is disclosed.

Further, in Patent Document 4, in a molten metal continuous casting facility, two hot water level meters are installed so as to measure symmetrical positions in the mold width direction around an immersion nozzle disposed in the center of the mold, and measurement thereof is performed. There is disclosed a hot water level detecting device that removes a standing wave component by obtaining an average value of values.

Further, in

Patent Documents

5 and 6, the structure of the control system based on the parametrization concept of the stabilization controller (a molten metal level deviation correction value calculation unit, an opening command correction value calculation unit, an opening change correction value calculation) Level of the continuous casting machine that is not affected by standing wave components by frequency shaping the sensitivity function into a notch filter by designing it based on robust control theory. A control method is disclosed.

Moreover, in patent document 7, the frequency of the periodicity level fluctuation | variation contained in the molten metal surface level signal is detected, and the opening degree change of the inlet to a mold is changed based on the signal which attenuate | damped the component of the detected frequency, and the deviation of a target level A level control that calculates the amount and generates a signal of the same frequency as the detected frequency that has a phase and amplitude that cancels periodic level fluctuations, and corrects the signal by adding it to the amount of change in opening. A method is disclosed.

JP 2007-260693 A JP 2009-241150 A JP 2010-69513 A JP 2005-28381 A JP 2001-129647 A JP 2002-248555 A JP 2002-59249 A

The amplitude of the standing wave that appears on the mold surface changes from moment to moment. On the other hand, in the method of Patent Document 2, it is assumed that the amplitude of the standing wave to be estimated is constant for a predetermined time. This is because the method of least squares is applied, but there is a problem that the response of the estimation is delayed, and the amplitude change of the standing wave cannot be followed.

In addition, in the method of Patent Document 3, the primary standing wave component is removed by installing a hot water level meter at the center of the mold, but mold powder is put near the opening on the upper surface of the mold. Since there is a device and it may be difficult to install a level meter in the center, it is desirable to remove the primary standing wave by signal processing.

Also, in the method of Patent Document 4, since two level meters must be installed, the installation cost and the maintenance cost are doubled compared to installing one level meter. In addition, because it is used in a severe environment at high temperatures, there is a difference between the two level meters, and there is a problem that the same level of the same level is different, and the accuracy of calibration for maintaining performance is required more than ever. Is done.

In the methods of

Patent Documents

5 and 6, the structure of the control system is defined based on the concept of parametrization of the stabilization controller, and the characteristics of the entire control system including the casting process (sensitivity function) using the robust control theory. ) Is shaped like a notch filter, and it is difficult to adjust the parameters of the control system because the structure is complex and the surface level signal from which standing waves have been removed cannot be observed. .

Further, the periodic fluctuation in the molten metal level signal that is the object of the method of Patent Document 7 is a bulging molten metal fluctuation, and is not a standing wave. Therefore, the molten metal level signal obtained by attenuating a specific frequency component is used for molten metal level control, and a signal that cancels the frequency component is generated and used for molten metal level control. That is, if the fluctuation level signal used for the molten metal surface level control includes periodic fluctuation, the calculation such as PID control becomes unstable, and the molten metal surface level fluctuation is amplified instead. The level signal is used for hot water level control. Then, since the fluctuation level control cannot be performed in the molten metal level control, the periodicity level is generated by generating a signal of the frequency component, adjusting the phase and amplitude, and adding it to the output of the molten metal level control. The fluctuation component is offset. For periodic level fluctuations that are not mass flow fluctuations such as standing waves, the molten steel flow rate to the mold must not be controlled by control, but when this method is applied, the molten steel flow rate to the mold is controlled at that frequency. This excites the rocking of the molten steel in the mold, strengthens the standing wave, and has an adverse effect on control.

The present invention has been made in view of the above. A bulging hot water to be originally controlled by using a single level meter and extracting and removing primary, secondary and tertiary standing wave components therefrom. An object of the present invention is to provide an in-mold molten steel surface level control method that realizes highly accurate molten metal surface level control by extracting only surface fluctuation and using it for molten metal surface level control.

In order to solve the above-described problems and achieve the object, the molten steel level control method in the mold according to the present invention is a unique method corresponding to the mold width in controlling the molten steel level in the mold of the continuous casting machine. A model of the molten metal level fluctuation due to a standing wave that oscillates with a period is represented by a secondary vibration system, and at least one of the deviation between the level measured value measured by the molten metal level meter and the output of the model and its differential value. The model is excited by feeding back to the input of the model, and the level change value measured by the level meter is estimated using the obtained output of the model to estimate the level fluctuation component due to the standing wave. The level signal from which the standing wave component is removed with the deviation between the model output and the flow rate of the molten steel flowing into the mold by feedback control using the level signal Characterized by operating the actuator to adjust.

Further, in the above-described invention, the molten metal level control method in the mold according to the present invention is such that the molten metal level meter is arranged at a position of the mold width 1/4 that is between the mold width center and the mold width end. It is characterized by being.

In addition, the molten steel level control method in the mold according to the present invention is a method for controlling the molten steel level in the mold of a continuous casting machine. The first-order standing wave model and second-order standing wave model of fluctuation are each represented by a second-order vibration system, and the difference between the level measurement value measured by the molten metal level meter and the output of the first standing wave model and its derivative. The primary standing wave model is excited by feeding back at least one of the values to the input of the primary standing wave model, and the primary standing wave is obtained by the obtained output of the primary standing wave model. A level signal obtained by removing the primary standing wave component with a deviation between the level measurement value measured by the level meter and the output of the primary standing wave model, The primary standing wave component The secondary standing wave model is excited by feeding back at least one of the deviation between the level signal thus removed and the output of the secondary standing wave model and the differential value thereof to the input of the secondary standing wave model. Then, the molten metal surface level fluctuation component due to the secondary standing wave is estimated from the output of the obtained secondary standing wave model, and the level signal from which the primary standing wave component has been removed and the secondary standing wave Operates an actuator that adjusts the flow rate of molten steel flowing into the mold by feedback control using the level signal, with the deviation from the model output as a level signal from which the primary standing wave component and the secondary standing wave component have been removed. It is characterized by doing.

Further, in the above-mentioned invention, the molten metal level control method in the mold according to the present invention is characterized in that the molten metal level meter has a mold width larger than a position of the mold width 1/4 that is intermediate between the mold width center and the mold width end. It is arranged at a position near the edge where a standing wave component can be taken.

In addition, the molten steel level control method in the mold according to the present invention is a method for controlling the molten steel level in the mold of a continuous casting machine. The first-order standing wave model, second-order standing wave model, and third-order standing wave model of fluctuation are each represented by a secondary vibration system, and the level measurement value measured by the molten metal level meter and the first-order standing wave model The primary standing wave model is excited by feeding back at least one of the deviation from the output and the differential value thereof to the input of the primary standing wave model. The molten metal level fluctuation component due to the primary standing wave is estimated based on the output, and the primary standing wave component is determined by the deviation between the level measurement value measured by the molten metal level meter and the output of the primary standing wave model. Is a level signal from which By feeding back at least one of the difference between the level signal from which the first-order standing wave component is removed and the output of the second-order standing wave model and the differential value thereof to the input of the second-order standing wave model, A level obtained by exciting a secondary standing wave model, estimating a level fluctuation component due to the secondary standing wave based on the output of the obtained secondary standing wave model, and removing the primary standing wave component A level signal obtained by removing the primary standing wave component and the secondary standing wave component with a deviation between the signal and the output of the secondary standing wave model, and the primary standing wave component and the secondary standing wave By feeding back at least one of the deviation between the level signal from which the wave component is removed and the output of the third-order standing wave model and its differential value to the input of the third-order standing wave model, the third-order standing wave The third-order standing wave model obtained by exciting the model The level fluctuation component due to the third-order standing wave is estimated from the output, and the level signal from which the first-order standing wave component and the second-order standing wave component are removed and the output of the third-order standing wave model A level signal from which the primary standing wave component, the secondary standing wave component, and the tertiary standing wave component have been removed is used as a deviation, and the flow rate of molten steel flowing into the mold is adjusted by feedback control using the level signal. It is characterized by operating an actuator.

In addition, the molten steel level control method in the mold according to the present invention is a method for controlling the molten steel level in the mold of a continuous casting machine. The model of fluctuation is expressed by a secondary vibration system, and the model is excited by feeding back the deviation between the level measurement value measured by the molten metal level meter and the output of the model to the state variable of the model. A level signal obtained by estimating the level fluctuation component due to the standing wave from the output of the model and removing the standing wave component with a deviation between the level measurement value measured by the level gauge and the output of the model. And operating an actuator for adjusting the flow rate of the molten steel flowing into the mold by feedback control using the level signal.

In addition, the molten steel level control method in the mold according to the present invention is a method for controlling the molten steel level in the mold of a continuous casting machine. The primary standing wave model and the secondary standing wave model of fluctuation are each expressed by a secondary vibration system, and the deviation between the level measurement value measured by the molten metal level meter and the output of the primary standing wave model is described as 1 above. The primary standing wave model is excited by feeding back to the state variable of the secondary standing wave model, and the surface level fluctuation component due to the primary standing wave is estimated from the obtained output of the primary standing wave model. And a level signal obtained by removing the primary standing wave component with a deviation between the level measurement value measured by the molten metal level meter and the output of the primary standing wave model, The removed level signal and the secondary determination The deviation from the output of the wave model is fed back to the state variable of the second-order standing wave model to excite the second-order standing wave model, and the second-order standing wave model is obtained according to the obtained output of the second-order standing wave model. The molten metal level fluctuation component due to standing waves is estimated, and the primary standing wave component and the secondary wave are determined with a deviation between the level signal from which the primary standing wave component is removed and the output of the secondary standing wave model. A level signal from which the standing wave component is removed is used, and an actuator for adjusting the flow rate of the molten steel flowing into the mold is controlled by feedback control using the level signal.

In addition, the molten steel level control method in the mold according to the present invention is a method for controlling the molten steel level in the mold of a continuous casting machine. The first-order standing wave model, second-order standing wave model, and third-order standing wave model of fluctuation are each represented by a secondary vibration system, and the level measurement value measured by the molten metal level meter and the first-order standing wave model The primary standing wave model is excited by feeding back the deviation from the output to the state variable of the primary standing wave model, and the primary standing wave is generated by the obtained output of the primary standing wave model. A level signal obtained by removing the primary standing wave component with a deviation between a level measurement value measured by the hot water level meter and an output of the primary standing wave model while estimating the molten metal level fluctuation component, Level with the primary standing wave component removed The secondary standing wave model is excited by feeding back the deviation between the signal and the output of the secondary standing wave model to the state variable of the secondary standing wave model. The level fluctuation component due to the secondary standing wave is estimated based on the output of the model, and the primary constant is determined by the deviation between the level signal from which the primary standing wave component has been removed and the output of the secondary standing wave model. A level signal from which the standing wave component and the secondary standing wave component have been removed is used, and the level signal from which the primary standing wave component and the secondary standing wave component have been removed and the output of the tertiary standing wave model The third-order standing wave model is excited by feeding back the deviation to the state variable of the third-order standing wave model, and the surface level of the third-order standing wave is obtained by the output of the obtained third-order standing wave model. While estimating the fluctuation component, the primary standing wave component and the 2 A level obtained by removing the primary standing wave component, the secondary standing wave component, and the tertiary standing wave component with a deviation between the level signal from which the standing wave component has been removed and the output of the tertiary standing wave model. It is characterized by operating an actuator that adjusts the flow rate of molten steel flowing into the mold by feedback control using the level signal.

The molten steel surface level control method in the mold according to the present invention represents the first, second, and third-order standing wave models as secondary vibration systems having respective frequencies as natural frequencies, their outputs, The output of the actual process to be compared to the level signal (in the first-order standing wave model, the level signal obtained by removing the first-order standing wave component from the level measurement value in the second-order standing wave model, and the third-order standing wave model) From the output of the model, a proportional differential operation is applied to the deviation from the level measurement value to the level signal from which the primary standing wave component and the secondary standing wave component have been removed, and the model is input to each model to excite the model. Standing wave component is estimated. At this time, the deviation between the model and the actual process becomes a level signal from which the corresponding standing wave component is removed. As described above, in the present invention, the standing wave component is extracted and the level signal from which the standing wave component is removed is performed in parallel. As a result, it is possible to adjust the damping constant of the secondary vibration system, which is the adjustment parameter in the present invention, and the gain of the proportional differential operation applied to the deviation while visually confirming the extraction status of the standing wave component. Wave extraction can be performed properly. The adjustment parameter corresponds to a selection characteristic (band width in a bandpass filter) in standing wave extraction, but since the relationship between each parameter and the characteristic is clear, the adjustment can be easily performed. Also have.

Further, the order of the standing wave to be extracted and removed may be selected according to the actual standing wave component included in the molten metal surface level measurement value. The standing wave component can be easily confirmed by frequency analysis of the measurement value of the molten metal level.

Further, unlike the

Patent Documents

5 and 6, the standing wave component removal of the present invention can be added to any hot water level control system, so there is no need to change the existing control system. . For example, if the hot water surface level control system is PI control, the hot water surface level signal used for PI control only needs to be the hot water surface level signal from which the standing wave component is removed according to the present invention. Moreover, it is possible to add not only to PI control but also to various known hot water level control systems.

FIG. 1 is an explanatory diagram showing a configuration example of an embodiment in which the present invention is applied to an in-mold molten steel surface level control system of a continuous casting machine. FIG. 2 is a block diagram showing the configuration of the standing wave component removal apparatus of the present embodiment. FIG. 3 is a diagram showing an example in which standing waves are extracted and removed according to the present embodiment. FIG. 4 is a diagram showing an example of the molten metal level fluctuation when the molten metal level control according to the present embodiment is performed. FIG. 5 is an explanatory view showing a configuration example of an embodiment in which the present invention is applied to a molten steel surface level control system in a mold of a continuous casting machine. FIG. 6 is a block diagram showing a transfer function of the first-order standing wave model. FIG. 7 is a block diagram illustrating a configuration example when primary standing wave removal is performed using the expression of FIG. FIG. 8 is an explanatory view showing a configuration of an example of a molten steel surface level control system in a mold of a conventional continuous casting machine. FIG. 9 is an explanatory diagram showing a standing wave. FIG. 10 is a diagram showing an example of the fluctuation of the molten metal level when the conventional molten metal level control is performed.

Hereinafter, an embodiment of a molten steel surface level control method in a mold according to the present invention will be described in detail based on the drawings. Note that the present invention is not limited to the embodiments.

First, the outline of the present invention will be described. In the present invention, a first-order and second-order standing wave model is represented by a secondary vibration system having respective frequencies as natural frequencies, and a standing wave that changes every moment according to the output is estimated. First, for the primary standing wave, the gain is multiplied by at least one of the level measurement value obtained by the level meter, the deviation of the output of the primary standing wave model and the differential value thereof, and used as the input of the primary standing wave model. provide feedback. As a result, the output of the primary standing wave model is an estimated value of the primary standing wave component every moment, so the deviation is obtained by removing the primary standing wave component from the level measurement value. At this time, by adjusting a gain multiplied by at least one of the deviation and its differential value, it is possible to set how much the frequency in the vicinity of the standing wave is to be estimated.

Next, for the secondary standing wave, the deviation between the level measurement value by the level meter and the output of the primary standing wave model, that is, the level measurement value from which the primary standing wave component has been removed and the secondary standing wave model At least one of the deviation and its differential value is multiplied by a gain and fed back to the input of the second-order standing wave model. As a result, the output of the secondary standing wave model is an estimated value of the secondary standing wave component every moment, so that the deviation is the secondary standing wave from the level measurement value from which the primary standing wave component has been removed. The wave component is removed. That is, it is possible to obtain a level signal obtained by removing the primary and secondary standing wave components from the measured value of the level meter. At this time, by adjusting a gain multiplied by at least one of the deviation and its differential value, it is possible to set how much the frequency in the vicinity of the standing wave is to be estimated.

When the molten metal level control is performed using the level signal obtained by removing the primary and secondary standing wave components obtained above, the control system does not react to the standing wave, so that the gain can be increased. It becomes possible to suppress bulging level fluctuations. Further, since only one level meter is required, installation and maintenance costs can be suppressed.

Next, FIG. 1 shows a configuration example when the present invention is applied to molten steel level control in a mold of a continuous casting machine. The same parts as those shown in FIG. 8 are denoted by the same reference numerals, and description thereof is also omitted. In FIG. 1, the standing wave component removing device 11 calculates a level signal from which the primary and secondary standing wave components have been removed from the surface level measurement value measured by the level meter 7, and sends it to the surface level control device 8. Output. The difference from the prior art of FIG. 8 is that, in this embodiment, the surface level measurement value measured by the surface level control device 8 with the level meter 7 is not used as it is, but is determined by the standing wave component removal device 11. The level signal from which the standing wave component is removed is used. Further, if the level meter 7 is intended only for the primary standing wave, the position of the node of the secondary standing wave (the position of the mold width 1/4 that is between the mold width center and the mold width end). However, if the primary and secondary standing waves are targeted, the position where the standing wave component can be taken closer to the mold width end (for example, the position of the mold width 1/8) ).

The standing wave component removal apparatus 11 is configured as shown in FIG. That is, the standing wave component removal apparatus 11 includes a primary standing wave model 12, a PD calculator 13, a secondary standing wave model 14, a PD calculator 15, and

adders

16 and 17. The first-order standing wave model 12 is a model of a first-order mode expressed by a second-order vibration system with respect to a molten metal surface level fluctuation caused by a standing wave oscillating at a specific period corresponding to the mold width. Frequency _{f 1} of the first-order standing wave is expressed by equation (1).

f ₁ = √ (G / 4πL) (1)
Here, G is the gravitational acceleration, and L is the mold width.

The transfer function G ₁ of the first-order standing wave model 12, a first-order standing wave frequency f ₁ is a secondary vibration system whose natural frequency is represented by the equation (2).

G ₁ = ω ₁ ² / (s ² + 2ζ ₁ ω ₁ s + ω ₁ ² ) (2)
Here, ω ₁ = 2πf ₁ and ζ ₁ is an attenuation coefficient.

The PD calculator 13 subjects the deviation calculated by the adder 16 from the output of the primary standing wave model 12 and the measured value of the level meter 7 to input to the primary standing wave model 12. Thereby, the primary standing wave model 12 is excited and outputs an estimated value of the primary standing wave component. At this time, the deviation (output of the adder 16) between the primary standing wave model 12 and the measured value of the level meter 7 becomes a level signal from which the primary standing wave component has been removed.

The secondary standing wave model 14 represents a model of a secondary mode with respect to a molten metal surface level fluctuation caused by a standing wave that oscillates at a specific period corresponding to the mold width, as a secondary vibration system. Frequency _{f 2} of the second-order standing wave is expressed by equation (3).

f ₂ = √ (G / 2πL) (3)

The transfer function G ₂ of a secondary standing wave model 14, the second-order standing wave frequency f ₂ a secondary vibration system with its natural frequency, is expressed by the equation (4).

G ₂ = ω ₂ ² / (s ² + 2ζ ₂ ω ₂ s + ω ₂ ² ) (4)
Here, ω ₂ = 2πf ₂ and ζ ₂ is an attenuation coefficient.

The PD calculator 15 calculates the deviation (output of the adder 16) calculated by the adder 16 from the output of the primary standing wave model 12 and the measurement value of the level meter 7, and the output of the secondary standing wave model 14. Are subjected to proportional differentiation on the deviation calculated by the adder 17 and input to the secondary standing wave model 14. As a result, the secondary standing wave model 14 is excited and outputs a secondary standing wave component estimation value. At this time, the deviation between the output of the primary standing wave model 12 and the measured value of the level meter 7 (the output of the adder 16) and the deviation of the output of the secondary standing wave model 14 (the output of the adder 17) are: The level signal is obtained by removing the primary and secondary standing wave components.

Thus, in the present embodiment, the standing wave component is extracted and the level signal from which the standing wave component is removed is performed in parallel. As a result, the attenuation constants ζ ₁ and ζ ₂ and the PD calculator 13 in the primary and secondary

standing wave models

12 and 14 which are the adjustment parameters in the present embodiment are confirmed while visually confirming the standing wave component extraction status. , 15 can be adjusted, so that standing wave extraction can be performed appropriately. The adjustment parameter corresponds to the selection characteristic (bandwidth in the bandpass filter) in the standing wave extraction, but the relationship between each parameter and the characteristic is clear, so that the adjustment can be easily performed.

FIG. 3 shows an example in which the primary and secondary standing wave components are extracted and removed from the surface level including the standing wave component according to the present embodiment. The standing wave component is removed from the molten metal level measurement value including the measurement noise caused by the standing wave, and the fluctuation of the molten metal surface level caused by bulging is clearly extracted.

Next, an example in which the hot water level control method according to the present invention is compared with the prior art is shown in FIGS. First, FIG. 10 shows a case where control is performed using the control system shown in FIG. 8, and PI control is used for the hot water level control device 8. As shown in FIG. 10, the opening of the sliding nozzle (S / N) 3 includes many fluctuation components due to standing waves included in the measured value of the molten metal level meter 7. Both the standing wave component and the bulging level level fluctuation appear in the surface level. To suppress bulging level level fluctuation, it is necessary to increase the gain of PI control. Then, the standing wave component appears more and more in the opening of the sliding nozzle (S / N) 3, which is the level level fluctuation. The gain cannot be increased.

On the other hand, FIG. 4 shows a case where the present embodiment shown in FIG. 2 is applied, and a level signal from which a standing wave component is removed is used. Therefore, the opening of the sliding nozzle (S / N) 3 is Since it does not appear greatly, the gain of the PI controller can be increased. Here, the proportional gain is 2.5 times that in the case of FIG. Therefore, the opening of the sliding nozzle (S / N) 3 can be appropriately operated in response to fluctuations in the level of the bulging hot water surface, and the water surface level fluctuation should be reduced to about 1/3 of the case of FIG. Was made.

In this embodiment, the processing is performed in the order of the first order and the second order. However, the first standing wave model 12, the PD calculator 13, the adder 16, the second standing wave model 14, and the PD calculation. The unit 14 and the adder 17 may be interchanged, and processing may be performed in the order of secondary and primary.

In addition, the standing wave normally has strong primary and secondary components, and the surface level control is performed using the level signal from which the primary and secondary standing wave components are removed as in this embodiment. However, if a third-order standing wave component is included, estimation and removal can be performed with the same configuration as that for the first-order and second-order components.

FIG. 5 shows the first-order, second-order, and third-order standing wave components. This mode model is expressed by a secondary vibration system. The frequency f ₃ of the third-order standing wave is expressed by equation (5).
f ₃ = √ (3G / 4πL) (5)

The transfer function G ₃ of a third-order standing wave model 18, the frequency f ₃ of the third-order standing wave is secondary vibration system whose natural frequency is represented by the equation (6).
G ₃ = ω ₃ ² / (s ² + 2ζ ₃ ω ₃ s + ω ₃ ² ) (6)
Here, ω ₃ = 2πf ₃ and ζ ₃ is an attenuation coefficient.

The PD calculator 19 is proportional to the deviation calculated by the adder 20 from the level signal from which the primary and secondary standing wave components output from the adder 17 are removed and the output of the tertiary standing wave model 18. The differential operation is performed and input to the third-order standing wave model 18. As a result, the third-order standing wave model 18 is excited and outputs a third-order standing wave component estimated value. At this time, the deviation between the output of the adder 17 and the output of the third-order standing wave model 18 (output of the adder 20) is a level signal from which the first-order, second-order, and third-order standing wave components have been removed.

The order of the standing wave to be extracted and removed may be selected in advance according to the actual standing wave component included in the molten metal level measurement value. The standing wave component can be easily confirmed by frequency analysis of the measurement value of the molten metal level. In addition, when the standing wave component up to the higher order is removed in this way, even if the standing wave component of a certain order decreases due to fluctuations in operating conditions, the standing wave component removed correspondingly Therefore, it is not necessary to change the configuration.

In carrying out the present invention, the differential calculation in the PD calculator may emphasize high-frequency components in the input signal and increase calculation errors. In order to prevent this, as described in claims 5 to 8, without using a PD calculator, the deviation of the surface level signal and the standing wave model is fed back to the state variable of the standing wave model (gain is set). It is effective to use a configuration of multiplying and adding.

FIG. 6 shows a block diagram representation of the transfer function of the first-order standing wave model of equation (2). The first-order standing wave model 12 is represented by a block diagram including two

integrators

21 and 22, two state feedback gains 23 and 24, and two

adders

25 and 26. The outputs of the

units

25 and 26 are the state variables of the model. FIG. 7 shows a configuration when primary standing wave removal is performed using the expression of FIG. The function of the PD calculator 13 is realized by two

gains

27 and 28. That is, a product obtained by multiplying the deviation calculated by the adder 16 from the output of the primary standing wave model 12 and the measured value of the level meter 7 by the gain 27 is fed back to the input of the integrator 21 via the adder 25. On the other hand, the product obtained by multiplying the deviation by the gain 28 is fed back to the input of the integrator 22 via the

adders

29 and 26, so that a calculation process equivalent to the proportional differential calculation can be performed. The

gains

27 and 28 correspond to a proportional term and a differential term, respectively, and their values a and b correspond to a proportional gain and a differential gain. Thereby, the primary standing wave model 12 is excited and outputs an estimated value of the primary standing wave component. At this time, the deviation (output of the adder 16) between the primary standing wave model 12 and the measured value of the level meter 7 becomes a level signal from which the primary standing wave component has been removed.

Similarly, for secondary and tertiary standing wave removal, the secondary and tertiary standing wave estimation in FIGS. 2 and 5 may be configured in the same manner as the primary standing wave estimation in FIG.

1 Mold 5 Molten Steel 6 Actuator 7 Level Meter 12 Primary Standing Wave Model 14 Secondary Standing Wave Model 18 Tertiary Standing Wave Model

Claims

When controlling the molten steel surface level in the mold of a continuous casting machine, a model of the molten metal surface level fluctuation due to the standing wave that oscillates with a specific period corresponding to the mold width is represented by a secondary vibration system.
The model is excited by feeding back at least one of a deviation between the level measurement value measured by the molten metal level meter and the output of the model and a differential value thereof to the input of the model, and the obtained output of the model By estimating the surface level fluctuation component due to the standing wave by the level signal obtained by removing the standing wave component with a deviation between the level measurement value measured by the level meter and the output of the model,
An in-mold molten steel surface level control method comprising operating an actuator for adjusting a flow rate of molten steel flowing into a mold by feedback control using the level signal.
2. The molten steel level level control method in a mold according to claim 1, wherein the molten metal level meter is arranged at a position of a mold width ¼ that is intermediate between a mold width center and a mold width end. .
When controlling the molten steel surface level in the mold of a continuous casting machine, the primary standing wave model and the secondary standing wave model of the molten metal surface level fluctuation due to the standing wave oscillating at a specific period corresponding to the mold width are used. Each is represented by a secondary vibration system,
By feeding back at least one of the deviation between the level measurement value measured by the molten metal level meter and the output of the primary standing wave model and the differential value thereof to the input of the primary standing wave model, The standing wave model is excited, and the level fluctuation component due to the primary standing wave is estimated from the obtained output of the primary standing wave model. A level signal obtained by removing the primary standing wave component with a deviation from the output of the primary standing wave model,
By feeding back at least one of a deviation between the level signal from which the primary standing wave component has been removed and the output of the secondary standing wave model and its differential value to the input of the secondary standing wave model, A level obtained by exciting a secondary standing wave model, estimating a level fluctuation component due to the secondary standing wave based on the output of the obtained secondary standing wave model, and removing the primary standing wave component A level signal obtained by removing the primary standing wave component and the secondary standing wave component with a deviation between the signal and the output of the secondary standing wave model;
An in-mold molten steel surface level control method comprising operating an actuator for adjusting a flow rate of molten steel flowing into a mold by feedback control using the level signal.
The hot water surface level meter is arranged at a position where a standing wave component can be taken closer to the mold width end than the position of the mold width ¼, which is intermediate between the mold width center and the mold width end. The in-mold molten steel surface level control method according to claim 3.
When controlling the molten steel surface level in the mold of a continuous casting machine, the primary standing wave model, the secondary standing wave model of the molten metal surface level fluctuation due to the standing wave oscillating at a specific period corresponding to the mold width, and Each 3rd-order standing wave model is represented by a secondary vibration system,
By feeding back at least one of the deviation between the level measurement value measured by the molten metal level meter and the output of the primary standing wave model and the differential value thereof to the input of the primary standing wave model, The standing wave model is excited, and the level fluctuation component due to the primary standing wave is estimated from the obtained output of the primary standing wave model. A level signal obtained by removing the primary standing wave component with a deviation from the output of the primary standing wave model,
By feeding back at least one of a difference between the level signal from which the primary standing wave component has been removed and the output of the secondary standing wave model and its differential value to the input of the secondary standing wave model, A level obtained by exciting a secondary standing wave model, estimating a level fluctuation component due to the secondary standing wave based on the output of the obtained secondary standing wave model, and removing the primary standing wave component A level signal obtained by removing the primary standing wave component and the secondary standing wave component with a deviation between the signal and the output of the secondary standing wave model;
At least one of a deviation between a level signal from which the primary standing wave component and the secondary standing wave component have been removed and an output of the tertiary standing wave model and a differential value thereof is used as the tertiary standing wave model. The third-order standing wave model is excited by returning to the input of the first-order wave, and the molten metal level fluctuation component due to the third-order standing wave is estimated from the output of the obtained third-order standing wave model. The primary standing wave component, the secondary standing wave component, and the tertiary are determined with a deviation between the level signal from which the standing wave component and the secondary standing wave component have been removed and the output of the tertiary standing wave model. A level signal from which standing wave components have been removed
An in-mold molten steel surface level control method comprising operating an actuator for adjusting a flow rate of molten steel flowing into a mold by feedback control using the level signal.
When controlling the molten steel surface level in the mold of a continuous casting machine, a model of the molten metal surface level fluctuation due to the standing wave that oscillates with a specific period corresponding to the mold width is represented by a secondary vibration system.
The model is excited by feeding back the deviation between the level measurement value measured by the molten metal level meter and the output of the model to the state variable of the model, and the molten metal surface by the standing wave is obtained by the output of the model obtained. Estimating the level fluctuation component, and a level signal obtained by removing the standing wave component with a deviation between the level measurement value measured by the molten metal level meter and the output of the model,
An in-mold molten steel surface level control method comprising operating an actuator for adjusting a flow rate of molten steel flowing into a mold by feedback control using the level signal.
When controlling the molten steel surface level in the mold of a continuous casting machine, the primary standing wave model and the secondary standing wave model of the molten metal surface level fluctuation due to the standing wave oscillating at a specific period corresponding to the mold width are used. Each is represented by a secondary vibration system,
Exciting the primary standing wave model by feeding back the deviation between the level measurement value measured by the molten metal level meter and the output of the primary standing wave model to the state variable of the primary standing wave model; The molten metal level fluctuation component due to the primary standing wave is estimated from the output of the obtained primary standing wave model, and the level measurement value measured by the molten metal level meter and the output of the primary standing wave model And a level signal from which the first-order standing wave component has been removed,
The secondary standing wave model is excited by feeding back the deviation between the level signal from which the primary standing wave component has been removed and the output of the secondary standing wave model to the state variable of the secondary standing wave model. Then, the molten metal surface level fluctuation component due to the secondary standing wave is estimated from the output of the obtained secondary standing wave model, and the level signal from which the primary standing wave component has been removed and the secondary standing wave A level signal obtained by removing the primary standing wave component and the secondary standing wave component with a deviation from the output of the model,
An in-mold molten steel surface level control method comprising operating an actuator for adjusting a flow rate of molten steel flowing into a mold by feedback control using the level signal.
When controlling the molten steel surface level in the mold of a continuous casting machine, the primary standing wave model, the secondary standing wave model of the molten metal surface level fluctuation due to the standing wave oscillating at a specific period corresponding to the mold width, and Each 3rd-order standing wave model is represented by a secondary vibration system,
Exciting the primary standing wave model by feeding back the deviation between the level measurement value measured by the molten metal level meter and the output of the primary standing wave model to the state variable of the primary standing wave model; Based on the obtained output of the primary standing wave model, the molten metal level fluctuation component due to the primary standing wave is estimated, and the level measurement value measured by the molten metal level meter and the output of the primary standing wave model And a level signal from which the first-order standing wave component has been removed,
The secondary standing wave model is excited by feeding back the deviation between the level signal from which the primary standing wave component has been removed and the output of the secondary standing wave model to the state variable of the secondary standing wave model. Then, the molten metal surface level fluctuation component due to the secondary standing wave is estimated from the output of the obtained secondary standing wave model, and the level signal from which the primary standing wave component has been removed and the secondary standing wave A level signal obtained by removing the primary standing wave component and the secondary standing wave component with a deviation from the output of the model,
By feeding back a deviation between the level signal from which the primary standing wave component and the secondary standing wave component are removed and the output of the tertiary standing wave model to the state variable of the tertiary standing wave model, A third-order standing wave model is excited, and a level fluctuation component due to the third-order standing wave is estimated from the output of the obtained third-order standing wave model, and the first-order standing wave component and the second-order wave are estimated. A level obtained by removing the primary standing wave component, the secondary standing wave component, and the tertiary standing wave component with a deviation between the level signal from which the standing wave component has been removed and the output of the tertiary standing wave model. Signal and
An in-mold molten steel surface level control method comprising operating an actuator for adjusting a flow rate of molten steel flowing into a mold by feedback control using the level signal.