JP5668301B2 - Temperature control method and temperature control apparatus for heating object - Google Patents

Description

  The present invention relates to a temperature control method and a temperature control device for a heating object such as a steel plate heated by a heating device.

  A continuous hot dip plating facility such as a steel plate is provided with a heating device that heats an object to be heated so that a metal plate such as a strip-shaped steel plate reaches a target temperature. The temperature control of the metal plate in the heating device is important in the production of the metal plate because it affects the quality of the metal plate as a product. As conventional metal plate temperature control techniques, for example, those described in Patent Documents 1 and 2 are known.

  The plate temperature control method described in Patent Document 1 calculates the operation amount change amount of the plate temperature adjusting unit for each feedforward control / feedback control gain that sets the calculated processing furnace outlet plate temperature to the target plate temperature. Then, from the calculated manipulated variable change amount and the heat balance model in the processing furnace body, the fluctuation of the plate temperature at the processing furnace outlet is predicted and calculated for each gain, and the predicted processing furnace outlet plate temperature and the target are calculated. Based on the temperature difference from the plate temperature and the operation amount change amount, an optimum operation amount change amount is determined from the operation amount change amounts calculated for each gain.

  The plate temperature control method described in Patent Document 2 performs feedforward control for changing the heating condition based on the heat transfer equation at a predetermined timing when a thermal load such as a plate thickness and a target plate temperature changes, and a predetermined time has elapsed. Thereafter, feedback control for correcting the heating condition according to the plate temperature deviation is performed with the heating condition set value as an initial value.

JP 2008-266715 A Japanese Patent Laid-Open No. 6-49546

  In the plate temperature control method described in Patent Document 1, the gain is forcibly adjusted so that the plate temperature measurement value at the outlet of the processing furnace body is fully trusted and the deviation from the plate temperature predicted value by the heat balance model becomes small. It will be out. Therefore, this plate temperature control method is a technique that can be applied only when the measurement error of the plate thermometer is allowed.

  On the other hand, in the plate temperature control method described in Patent Literature 2, after a predetermined time has elapsed, feedback control is performed to correct the heating condition according to the plate temperature deviation with the heating condition set value as an initial value. It is a major premise that the detected plate temperature is measured with desired accuracy.

  However, since it is difficult to measure the temperature of a metal plate such as a steel plate with a contact-type thermometer due to problems such as surface scratches, radiation thermometers that can measure temperature without contact are often used. The thermometer has a problem that high-precision temperature measurement cannot be performed depending on the surface property of the object to be measured. In particular, radiation thermometers are often not practical when they are mirror-like and have low emissivity, such as steel plates. In Patent Document 2, it is not assumed that a thermometer with poor measurement accuracy is used.

  Therefore, in the present invention, even in a heating process in which temperature measurement with a desired accuracy cannot be expected with a thermometer due to the low emissivity of a heating object such as a steel plate, and modeling with the desired accuracy is difficult. It is an object of the present invention to provide a temperature control method and a temperature control apparatus capable of performing highly accurate temperature control.

Temperature control method for heating an object of the present invention, there is provided a temperature control method for heating an object of the steel sheet is heated by passing plate continuously to the heating device the steel sheet, continuously Tsuban the steel plate heating apparatus When the heat treatment is performed, the output value of the heating device (hereinafter referred to as “model calculation”) is calculated by calculating the heat balance model in the heating device from the required temperature rise of the steel plate obtained from the target temperature of the steel plate and the inlet temperature of the heating device. The temperature after heating of the steel sheet by the heating device is measured with a radiation thermometer, and the output value of the heating device is controlled by temperature feedback control from the deviation between this measurement result and the temperature target value of the steel plate. (hereinafter. referred to as "temperature feedback control value") to calculate a temperature feedback control output values, control the limiter limiting value is set from empirically confirmed normal model error range Is the fact, when outputting the command model calculated value to the heating device, characterized in that it comprises corrected by temperature feedback control value.

According to the present invention, the output value (model calculation value) of the heating device is estimated by model calculation from the required temperature rise of the steel plate , and the heating device is mainly controlled based on the model calculation value with desired accuracy. The model error can be eliminated by using the measured value of the thermometer, which is not expected to measure the temperature, for the correction of the model calculation value by the auxiliary temperature feedback control.

The temperature feedback control output value Ru is limited by the limiter. By limiting the temperature feedback control output value, correction by the temperature feedback control output value is not performed beyond the model error, and it is possible to prevent the correction from being applied without limit.

Upon the temperature control device of the present invention, there is provided a temperature control apparatus for steel plates heated by passing plate continuously to the heating device the steel sheet, continuously subjected to heat treatment by Tsuban the steel plate heating apparatus, steel Required power calculation model to estimate the output value (model calculation value) of the heating device by the heat balance model calculation in the heating device from the required temperature rise of the steel plate obtained from the temperature target value of the heater and the inlet side temperature of the heating device And the temperature after heating the steel sheet by the heating device is measured with a radiation thermometer, and the output value of the heating device (temperature feedback control output value) is calculated by temperature feedback control from the deviation between this measurement result and the temperature target value of the steel plate a limiter for limiting the temperature feedback control output value and the temperature feedback control means, the restriction value set from empirically confirmed normal model error range, model Upon the calculated value and outputs the command to the heating device, is intended to include a correction means for correcting the temperature feedback control value model calculated values.

According to the present invention, the main object is to estimate the output value (model calculated value) of the heating device by model calculation from the required temperature rise of the steel sheet by the required power calculation model and control the heating device based on this model calculated value. The model error can be eliminated by supplementarily calculating the measured value of the thermometer that is not expected to measure the temperature with the desired accuracy by the temperature feedback control means and using the correction means to correct the model calculation value. it can.

The temperature control apparatus of the present invention, Ru der further contains a limiter for limiting the temperature feedback control output value. Thus, by limiting the temperature feedback control output value, correction by the temperature feedback control output value is not performed beyond the model error, and it is possible to prevent the correction from being applied indefinitely.

  According to the present invention, it is possible to perform highly accurate temperature control even in a heating process in which desired accuracy cannot be satisfied by each of temperature control based on a model calculation value and temperature feedback control based on a thermometer measurement value.

It is a schematic block diagram of the steel plate surface treatment line in embodiment of this invention. (A) is a figure which shows the temperature controllability of the temperature control apparatus in this embodiment, (b) is a figure which shows the temperature controllability in the case of only temperature control based on a model calculation value, (c) is the temperature by a thermometer measured value It is a figure which shows the temperature control property in the case of only feedback control.

FIG. 1 is a schematic configuration diagram of a steel sheet surface treatment line in an embodiment of the present invention.
As shown in FIG. 1, the steel sheet surface treatment line according to the embodiment of the present invention includes a transport roller 2 that continuously transports the steel sheet 1, and a near infrared (NIR) heater as a heating device that heats the steel sheet 1 ( 3), a radiation thermometer 4 that is a thermometer that measures the temperature of the steel sheet 1 as a measurement object in a non-contact manner, and a temperature control device 5 that controls the heating temperature of the heater 3. Have

  The heater 3 is for heating the steel plate 1 coated with a coating liquid such as an organic resin, and performing drying or film formation after the surface treatment. In addition to the NIR, the heater 3 can use a method such as resistance heating or infrared heating. The radiation thermometer 4 measures the temperature of the steel plate 1 after the heat treatment by the heater 3 in a non-contact manner.

  The temperature control device 5 includes a required power calculation model 10 for estimating an output value (hereinafter referred to as a “model calculation value”) that is a required power of the heater 3 by model calculation from a required temperature increase amount of the steel plate 1, and a radiation temperature. The temperature FB control means 11 for calculating the output value of the heater 3 (hereinafter referred to as “temperature FB control output value”) from the deviation between the measurement result by the meter 4 and the temperature target value, and is output by the temperature FB control means 11. And a limiter 12 for limiting the temperature FB control output value.

  More specifically, the required power calculation model 10 includes steel plate size (plate width, plate thickness), plate speed (line speed), specific heat, steel plate conditions such as heating efficiency and temperature target value, and the inlet side temperature (estimated) of the heater 3. The output value of the heater 3 is calculated by model calculation from the required temperature rise ΔT obtained from the value). The required power calculation model 10 is executed at a constant cycle (for example, 20 sec. Cycle by a PLC (programmable logic controller)).

  In the steel plate surface treatment line having the above-described configuration, when the steel plate 1 is continuously passed through the heater 3 and heat treatment is performed, the temperature control device 5 calculates the steel plate from the temperature target value of the steel plate 1 and the inlet temperature of the heater 3. 1 is calculated, and the output value (model calculation value) of the heater 3 is estimated from the required temperature increase amount ΔT and the above-described steel plate conditions by the required power calculation model 10 and is mainly based on this model calculation value. To control the heater 3.

  At this time, the temperature control device 5 calculates the temperature feedback control output value by the temperature FB control means 11 from the deviation between the temperature of the steel plate 1 measured by the radiation thermometer 4 on the outlet side of the heater 3 and the temperature target value, and the model The model calculation value is corrected by adding to the calculation value. The summing point 13 in FIG. 1 functions as a correction unit that corrects the model calculation value with the temperature FB control output value and issues an output command to the heater 3. Since the temperature feedback control output value is limited by the limiter 12, no correction beyond the model error is performed.

  Here, since the temperature FB control means 11 is intended to remove the steady-state deviation due to the model error, the measured value of the radiation thermometer 4 is filtered to remove the noise, and the differential element is As a non-use, the gain setting is mainly based on integral elements. The limiter 12 is set with a normal model error range confirmed empirically, for example, a limit value confirmed by investigating the actual state of the model error using a contact thermometer in advance. As a result, correction by the temperature FB control means 11 is not applied beyond the confirmed model error.

  Thus, in the temperature control device 5 in the present embodiment, the output value (model calculation value) of the heater 3 is estimated by model calculation from the necessary temperature increase ΔT of the steel plate 1, and the heater 3 is determined based on this model calculation value. Mainly controlling the temperature, the measurement value of the radiation thermometer 3 that cannot expect the temperature measurement with the desired accuracy is used for correcting the model calculation value by the temperature feedback control simultaneously in parallel, thereby eliminating the steady deviation due to the model error can do.

  Therefore, in the temperature control device 5 in the present embodiment, it is possible to perform highly accurate temperature control even in a heating process in which the desired accuracy cannot be satisfied by the temperature control based on the model calculation value and the temperature feedback control based on the thermometer measurement value alone. It is.

  In addition, when controlling under such a condition only by temperature feedback control as in the past, it takes a long time to converge to the target temperature when the heating condition changes, but the temperature control device in this embodiment 5 is used in combination with the model calculation value, so most of the power change required when the condition changes is performed in a timely manner based on the model calculation result, and the temperature feedback control is performed for the steady deviation due to the model error. It will contribute to elimination.

  Further, in the present embodiment, the model calculation is executed not only at the preset but also at a constant cycle, so that temperature control can be performed in a timely manner even when the target temperature, the size of the steel plate 1 and the processing speed vary. However, since this causes a difference between the target temperature due to an error between the model and the actual process, by adding the correction by the temperature FB control means 11 to the model calculation value as described above, the output command value of the heater 3 is obtained. The error is eliminated.

  As described above, in the temperature control device 5 according to the present embodiment, the temperature feedback control and the temperature control based on the model calculation value are always executed in parallel. It is possible. In particular, in a highly responsive process such as a steel plate surface treatment line as in this embodiment, it is possible to correct the model error even during the transient period of line acceleration / deceleration. It is more suitable than the method of switching between word control and feedback control.

  Although the actual measured value can be used as the inlet side temperature of the heater 3, the steel sheet surface treatment line as in the present embodiment has many fluctuation factors of the inlet side temperature, so that the desired accuracy is the same as the outlet side temperature. There are many cases that cannot be measured with. Therefore, in this embodiment, a calibration curve for estimating the inlet temperature is created and the estimated value is used.

  In the steel plate surface treatment line, there is a section passing through the water tank in front of the heater 3, and the plate temperature is affected by the water temperature there. Therefore, the inlet side temperature is a contact type using the water tank temperature, the plate thickness and the atmospheric temperature as parameters. A calibration curve is created from the results of measurement with a thermometer, and the estimated input side temperature is read from the actual values of these parameters during operation and used as the input temperature of the heater 3.

  In the present embodiment, an NIR heater is used as the heater 3. However, since several hundred lamps are heating sources, the NIR heater can be operated even if it is disconnected a little. At this time, the output command to the heater 3 is performed regardless of the presence or absence of disconnection, and only the output voltage of the power source (thyristor) is changed. Therefore, this can be dealt with by detecting the number of disconnections of the NIR heater and changing the limit value of the limiter 12 in accordance with the disconnection state.

  Further, when the output of the radiation thermometer 4 decreases due to dirt or the like, the temperature change (ΔT) with respect to the power change (ΔP) of the heater 3 also decreases. Therefore, except for the part where the line speed fluctuates, ΔT with respect to ΔP is logged, and compared with the current situation, if the temperature change becomes dull, it is determined that there is a concern about contamination of the radiation thermometer 4, and the positive side It is also possible to adopt a configuration in which the upper limit of the temperature FB control output value is set low.

  The temperature controllability of the temperature control device 5 in the present embodiment that uses both temperature control based on the model calculation value and temperature feedback control based on the thermometer measurement value was verified. FIG. 2A shows the temperature controllability of the temperature control device 5 in this embodiment. FIG. 2 shows, as a comparative example, an example (b) only for temperature control based on model calculation values and an example (c) only for temperature feedback control based on thermometer measurement values.

  As shown in FIG. 2 (b), in the case of only temperature control based on the model calculation value, the required power increases simultaneously with the line speed change (strictly, there is a delay in the control cycle) by the model calculation. The followability is good, but steady deviations due to model errors are inevitable. In addition, the steady deviation increases as the mass of the object to be heated increases.

  In addition, as shown in FIG. 2C, in the case of only temperature feedback based on a thermometer measurement value, the reaction is slow because the NIR output changes according to the PID gain only when a temperature deviation occurs due to a change in line speed. For this reason, when the accuracy of the thermometer is poor and the filtering process and the integration element are mainly used, the reaction becomes particularly gentle.

  On the other hand, as shown in FIG. 2A, in the temperature control device 5 in the present embodiment, when acceleration is performed from a state in which the steady deviation is eliminated by the temperature feedback element, the steady deviation is temporarily reduced due to a model calculation error with respect to the acceleration. Although it occurs, the steady-state deviation is eventually eliminated by the temperature feedback mainly of integration.

  As described above, in the temperature control device 5 according to the present embodiment, even when temperature measurement with a desired accuracy by the thermometer cannot be expected, the temperature control based on the conventional model calculation value and the temperature feedback control based on the thermometer measurement value are performed. It was confirmed that it was possible to eliminate steady-state deviations that could not be solved by each single unit, and that it was possible to perform highly accurate temperature control.

  INDUSTRIAL APPLICABILITY The present invention is useful as a temperature control method and a temperature control device for an object to be heated that is heated by a heating device in a continuous hot dip plating facility such as a steel plate.

DESCRIPTION OF SYMBOLS 1 Steel plate 2 Conveyance roller 3 Heater 4 Radiation thermometer 5 Temperature control apparatus 10 Required power calculation model 11 Temperature FB control means 12 Limiter

Claims (2)

A method for controlling the temperature of the steel sheet, in which the steel sheet is continuously passed through a heating device and heated.
When performing the heat treatment by continuously passing the steel plate through the heating device, the inside of the heating device is calculated from the required temperature rise of the steel plate obtained from the temperature target value of the steel plate and the inlet side temperature of the heating device. Estimating the output value of the heating device (hereinafter referred to as “model calculation value”) by heat balance model calculation in
The temperature after heating of the steel sheet by the heating device is measured by a radiation thermometer, and the output value of the heating device (hereinafter referred to as “temperature feedback control”) by temperature feedback control from the deviation between the measurement result and the temperature target value of the steel plate. Output value ”),
The temperature feedback control output value is limited by a limiter in which a limit value is set from a model error range confirmed by investigating using a contact thermometer in advance .
A temperature control method including correcting the model calculation value with the temperature feedback control output value when outputting the model calculation value to the heating device. A temperature control device for the steel plate that continuously heats the steel plate through a heating device,
When performing the heat treatment by continuously passing the steel plate through the heating device, the inside of the heating device is calculated from the required temperature rise of the steel plate obtained from the temperature target value of the steel plate and the inlet side temperature of the heating device. A required power calculation model for estimating the output value of the heating device (hereinafter referred to as “model calculation value”) by heat balance model calculation in
The temperature after heating of the steel sheet by the heating device is measured by a radiation thermometer, and the output value of the heating device (hereinafter referred to as “temperature feedback control”) by temperature feedback control from the deviation between the measurement result and the temperature target value of the steel plate. A temperature feedback control means for calculating the output value,
A limiter for limiting the temperature feedback control output value by a limit value set from a model error range confirmed by investigating in advance using a contact thermometer ;
A temperature control device comprising: correction means for correcting the model calculation value by the temperature feedback control output value when the model calculation value is output to the heating device.

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