JPH0527122B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical Field of the Invention] The present invention relates to a running material temperature control device for a heat treatment furnace that improves the controllability of the exit side material temperature in response to changes in the material passing capacity of a continuous heat treatment furnace, for example. [Technical Background of the Invention] In a heat treatment furnace used in the metal industry field, it is essential to maintain a uniform temperature of the material at the exit side of the heating or cooling furnace in order to improve the quality of the product. By the way, in controlling the material temperature at the exit side of this type of continuous heat treatment furnace, the passing capacity determined by the passing speed of the material, the width and thickness of the material (in rare cases, the quality of the material is also involved) is constant. For example, it is possible to obtain a somewhat uniform outlet material temperature simply by using a feedback control system. However, in recent years, products in this field have become more diverse, and in continuous processing furnaces, materials of different widths and thicknesses are often connected and passed through the furnace continuously. There are many changes in the material speed to match the through-furnace capacity, and it is no longer possible to obtain a uniform outlet material temperature using only the feedback control system. FIG. 1 is a block diagram of a conventional conventional continuous heat treatment furnace exit side material temperature control device, and here specifically shows the case of a steel plate heating furnace.
That is, the steel plate 1 is continuously run through a plurality of rolls 3 arranged in a heating furnace 2, and after being heat-treated by a heating section 4 such as a burner during the run, it is heated from the furnace outlet side. Output. The temperature of the heat-treated steel sheet 1 is detected by a temperature detector 5 installed near the exit side of the furnace and sent to a temperature controller 6. This temperature controller 6 has a detection temperature and a set temperature.
After performing a comparison adjustment operation with SV to obtain a temperature adjustment output signal, it is supplied to the addition section 7. On the other hand, the width signal W and the thickness signal t of the steel plate 1 are supplied to this device in advance, and these two signals W,
After t is multiplied by the multiplier 8, the switching circuit 9
The data is sent to the memory section 10 via the. The switching circuit 9 is
When it receives a signal from the material change part detector 11 indicating that the change part A of the steel pipe 1 has passed, it turns on and stores the multiplication output from the multiplication part 8 in the memory part 10. The signal (W×t) stored in the memory unit 10 is inputted to the multiplication unit 13 together with the passing speed signal v from the passing speed detector 12 of the steel plate 1 and the coefficient K, where each signal W, t, Multiplication of v and K is performed. moreover,
The multiplied signal obtained by the multiplier 13 is extracted as a disturbance compensation signal via the feed forward model 14 and then supplied to the adder 7. This adder 7 adds the disturbance compensation signal and the temperature adjustment output signal from the temperature controller 6, uses this added value as a setting signal for the combustion control system, and uses the added value as a setting signal for the fuel flow controller 15 and the ratio setting unit 16. A ratio calculation is performed using the following formula, and each air is supplied to the air flow rate controller 17. These controllers 15 and 17 compare the setting signal with the fuel flow rate and air flow rate detected by each flow rate detector 18 and 19, and adjust the fuel flow rate control valve 20 and air flow rate so that each deviation becomes zero. By controlling the opening degree of the flow control valve 21, desired amounts of fuel and air are supplied to the heating section 4, and the temperature of the steel plate on the exit side of the furnace is controlled to a predetermined temperature. [Problems in the Background Art] By the way, fluctuations in the material passing capacity, which is determined by the material passing speed, material width, and material thickness, of a continuous heat treatment furnace appear as disturbances in the material temperature control on the exit side. This greatly affected the quality of the material because it caused the material temperature to fluctuate greatly. Moreover, as the line speed increases, the influence of temperature changes on quality becomes even greater. For this reason, when the furnace passing capacity of the material changes, it is necessary to suppress the fluctuation in the temperature of the material on the outlet side as small as possible. In other words,
reducing transient fluctuations to near the limit;
It is necessary to ensure control stability in each furnace capacity band (load band). However, in the conventional apparatus, the above two requirements are satisfied only in the case of the furnace passing capacity at one specific point, and the above requirements are not satisfied in the case of other furnace passing capacities. In other words, the conventional equipment does not perform any gain correction of the feedback control system while combining feedback, so although it is sufficient to adjust the specific point of the passing capacity obtained by adjustment, the passing capacity may increase or decrease. When this happens, it deviates from the optimum point by the amount of increase or decrease, and there is a fatal flaw in that the transient control characteristics and controllability in each load band also deteriorate. In the future, line speed will increase,
As plate widths and plate thicknesses tend to become more diverse, their transient control characteristics are becoming increasingly worse, and it has been difficult to find adequate countermeasures. [Object of the Invention] The present invention has been made with attention to the above-mentioned points, and it changes the control amount of the feed forward control system to an optimal value in response to changes in the furnace passing capacity of the material, and
Therefore, it is an object of the present invention to provide a running material temperature control device for a heat treatment furnace that improves transient control characteristics and corrects the gain of a feedback control system to an appropriate value. [Summary of the Invention] The present invention heat-treats a material running in a heat treatment furnace using a feedback control system, and controls the temperature of the material on the exit side of the furnace to a predetermined temperature. , the multiplication signal of the width and thickness of the material, which is set and input as the width and thickness of the material changes, is taken in by the material change part detection timing, and the furnace speed of the material is added to this taken signal. A disturbance compensation signal for gain correction of the feedback control system is obtained by multiplying by
Multiply the signal obtained by subtracting the furnace entry side material temperature from the set temperature, pass the obtained signal through a feed forward model to obtain a static/dynamic characteristic compensation signal, and use this to calculate the setting signal for the secondary controller of the feedback control system. This is a running material temperature control device for heat treatment furnaces used for [Embodiments of the Invention] FIG. 2 is a diagram showing the basic configuration of the present invention. This figure shows a specific example applied to a steel plate heating furnace, similar to Fig. 1, in which either one of the plate width and plate thickness is
A material, for example, a steel plate 31 having one or both of the different changed portions A, is shown approaching the vicinity of the furnace inlet of the heating furnace 32. The tip side of the steel plate 31, that is, the tip side of the steel plate having a small plate width and thickness, is run, for example, in a meandering manner via a plurality of rolls 33, etc. arranged inside a heating furnace 32 as shown in the figure. After being heat-treated in the heating section 34 during the process, it is outputted from the furnace outlet side. Reference numeral 35 denotes a change part detector for detecting the passing of a change part A in plate width, plate thickness, etc. of the steel plate 31 installed near the furnace inlet side, and 36 refers to a rotating body such as the roll 33 installed near the furnace inlet. A furnace passage speed detector 37 for the steel plate 31 is provided, and a temperature detector 37 detects the temperature of the steel plate 31 installed near the outlet in the furnace. When the changing portion detector 35 detects the changing portion A of the steel plate 31, the changing portion detector 35 inputs it to the switching circuit 38 as a control amount change timing signal for the feedforward control system and performs ON control. This feed forward control system includes a multiplier 39 that multiplies the width signal W of the steel plate 31 and the plate thickness signal t, which are set and input as the steel plate 31 changes, and a multiplier when the switching circuit 38 is turned on. 39
A memory section 40 stores the multiplication signal from the memory section 40, and the multiplication signal (W x t) of the memory section 40 is multiplied by the furnace speed and coefficient K from the speed detector 36 to perform disturbance compensation for gain correction of the feedback control system. It consists of a multiplier 41 that obtains a signal, and a feedforward model 42 that obtains a static characteristic and dynamic characteristic compensation signal from this disturbance compensation signal. The feedback control system includes a temperature controller 43 as a primary controller that obtains a temperature adjustment output signal by comparing the set temperature SV and the detected temperature from the furnace outlet temperature detector 37 and performing adjustment calculations; A gain correction calculation unit 44 multiplies the outputs of 43 in total by a disturbance compensation signal to obtain a temperature control output signal with gain correction, and a gain correction calculation unit 44 that multiplies the outputs of 43 in total and a disturbance compensation signal to extract a temperature control output signal with gain correction. a signal converter 45 that obtains a setting signal;
This setting signal is used to control the combustion of the heating section 34, and is comprised of a combustion control system 46. This combustion control system 46 connects each flow rate signal of a fuel flow rate detector 461 and an air flow rate detector 462 to a signal conversion section 45.
The flow rate controllers 463 and 464 as secondary controllers perform comparison adjustment calculations with the setting signal from the controller to obtain a flow rate adjustment output signal, which is added to each control valve 465 and 466 to determine the amount of fuel to be supplied to the heating section 34. It also has the function of controlling the amount of air. 467 is a ratio setting section. Next, FIG. 3 is a detailed diagram of the feedforward model 42 and signal converter 45 of FIG. 2.
That is, these configurations include a difference calculation section 51 that obtains a static characteristic compensation signal by using the difference between the previous disturbance compensation signal and the current disturbance compensation signal, an addition section 52, a velocity type-position type signal conversion section 53, and a disturbance compensation signal. It consists of an incomplete differentiation section 54 that obtains a signal that is incompletely differentiated from the signal, a broken line section 55 that provides directionality, and an addition section 56. Therefore, in the configuration shown in FIG. 3, the disturbance compensation signal D _o from the multiplication section 41 is introduced into the difference calculation section 51, a static characteristic compensation signal is obtained from the difference between the previous time and this time, and this compensation signal is combined with the gain correction. The adder 52 adds the temperature control output signal and the adder 52 .
The velocity type signal from the subsequent position type signal converter 53
is converted into a velocity-position signal. Further, the disturbance compensation signal D _o is introduced into the incomplete differentiator 54,
Here, the imperfectly differentiated signal is extracted. An incompletely differentiated signal is a signal centered at zero,
Specifically, when the compensation signal D _o is constant, the incompletely differentiated output is zero, when the furnace capacity is at its upper limit, the incompletely differentiated output is greater than zero, and when it falls, it is less than zero. The incomplete differential output obtained in this way is input to the broken line section 55, where a signal with directionality is created by setting the broken line, and this signal and the output of the position signal conversion section 53 are added to the addition section. 56, the setting signal for the combustion control system 46 is obtained. Next, the operation of the apparatus having the configuration shown in FIGS. 2 and 3 will be explained. That is, if the steel plate 31 to be heat treated in the heating furnace 32 has a changed part A in either one or both of the width and thickness, the changed part detector 35 detects the changed part A of the steel plate 31 and switches. The circuit 38 is turned on. This switching circuit 38
When turned on, the plate width signal W that is set and input as the steel plate 31 changes and is multiplied by the multiplier 39
A multiplied signal of the thickness signal t and the plate thickness signal t is stored in the memory section 40 via the switching circuit 38. The signal (W×t) stored in the memory unit 40 is sent to the multiplier 41 along with the furnace passing speed and coefficient K from the speed detector 36.
multiplied by and extracted as the disturbance compensation signal D _o ,
This is given as a gain correction signal to the temperature control output signal of the temperature controller 43, which is the primary controller of the feedback control system. Therefore, the gain correction calculation section 44 outputs a temperature adjustment output signal with gain correction. Further, the disturbance compensation signal obtained by the multiplication section 41 is introduced into a feedforward model 42 and a signal conversion section 45, which will be specifically described in FIG.
Here, a static characteristic compensation signal and a dynamic characteristic compensation signal are obtained, and the speed type signal is further converted into a position type signal.
is determined as the setting signal. Therefore, each of the flow rate controllers 463 and 464 takes in the detected fuel flow rate and the detected air flow rate, and obtains a final flow rate adjustment output signal by comparing and adjusting the set signal with the detected flow rate, and based on this signal. Each valve 465,466
A desired amount of fuel and air is fed into the heating section 34 by adjusting the opening degree of the opening, and heat treatment is performed so that the temperature of the material on the exit side of the furnace reaches a predetermined temperature. Next, one embodiment of the present invention will be described with reference to FIG. Since the basic configuration of this device is the same as that shown in FIGS. 2 and 3, the same parts are given the same reference numerals and a detailed explanation thereof will be omitted, and the different parts will be described below. That is, in this device, a furnace entry side material temperature detector 61 is added to the device shown in FIG.
, a subtraction unit 62 that subtracts the temperature detected by the material temperature detector 61 from the set temperature of the temperature controller 43, and an input signal to the feed forward model 42 is obtained by multiplying this subtraction output by a disturbance compensation signal. Multiplication section 6
3 has been newly established. Next, the apparatuses according to the first and second inventions will be specifically explained using mathematical formulas. Now, the specifications of the material temperature control system of the continuous heat treatment furnace are determined as follows.

[Table] Therefore, in order to maintain the furnace outlet side temperature T ₀ at a predetermined value, the process requirement, that is, the temperature control output signal
MV can basically be expressed using equation (1). MV∝D×W×V×(T _s −T _i +T _c ) =K・d・w・v・(t _s −t _i +t _c )……(1) However, T _c (℃), t _c (%) is the temperature control output signal of the material on the exit side of the furnace, and K is the proportionality constant. Note that equation (1) expresses only static relationships, so if we include dynamic relationships as well, we get MV=d・w・v・G _f・(t _s −t _i +t _c )... (2) = d・w・v・G _f・(t _s −t _i ) +d・w・v・G _f・t _c ……(3). G _f indicates the feed forward model 42. Therefore, the transfer function block diagram of the material temperature control system based on equation (3) can be expressed as shown in FIG. In this block diagram, (t _s − t _i )=
Certain cases correspond to the first invention, and the effects related to the invention will be explained below using mathematical formulas. Now, the temperature of the material on the exit side of the furnace t _p , the fuel flow rate f _f and the temperature control output signal t _c of the material on the exit side of the furnace are as follows: t _p = -d・w・v・(t _s −t _i )・G _d +f _f・G _p ...(4) f _f =d・w・v・{(t _s −t _i )・G _f +t _c・G _f }
...(5) t _c = (t _s − t _p )・G _c1 ...(6) It can be expressed as. In the above equation, G _p is the transfer function between the combustion control system setting signal of the furnace process and the temperature of the material on the exit side of the furnace, G _d is the transfer function between the material width w, thickness d, and furnace passing speed v, and G _c1 is the temperature controller 43 transfer function. In Fig. 5, G _c2 is the fuel flow controller 463
G _c3 is the transfer function of the air flow controller 464. Therefore, from equations (4) to (6), the temperature of the material on the exit side of the furnace t _p
is, t _p = 1/1 + G _f・G _p・d・w・v・G _c1 {G _f・G _p・d・w・v・G _c1・t _s +(t _s −t _i )・d・w・
v・(G _f・G _p −G _d )} ... can be derived by the equation (7). From this formula, set temperature
t _s , temperature of the material on the furnace entry side t _i , width w and thickness d of the material,
In order to keep the furnace exit side material temperature t _p at a constant value even if any of the furnace passage speeds v changes, (t _s −t _i )・d・w・v・(G _f・G _p −G _d )=0...(8) should hold true. Therefore, G _f = G _d / G _p (9) can be found. Here, G _f , G _p , and G _d can be determined experimentally. In general, it can be expressed as a composite of dead time and a first-order delay with a time constant, so G _p = K _p /1 + T _p・se ^-Lp

Claims (1)

[Scope of Claims] 1. By performing heat treatment on the material traveling in the heat treatment furnace using a feedback control system consisting of a temperature controller as a primary controller and a combustion control system as a secondary controller, In a running material temperature control device for a heat treatment furnace that controls the temperature of the material on the exit side of the heat treatment furnace to a predetermined temperature, upon receiving a detection signal for passing the material through a changing portion generated from a changing portion detector installed on the furnace entry side, Width signal w and thickness input corresponding to changes in the width and thickness of the material among the furnace passing capacity determined by at least the furnace passing speed v of the material, the width w and the thickness d of the material Disturbance compensation signal acquisition means for obtaining a gain correction disturbance compensation signal which is a signal w, d, v proportional to the weight flow rate by multiplying the signal multiplied by the signal d by the furnace passing speed v of the material; Signals w, d, v proportional to the weight flow rate obtained by the acquisition means are multiplied by the temperature adjustment output signal output from the primary controller based on the difference between the detected temperature on the furnace exit side and the set temperature. a gain correction calculation means for obtaining a feedback control output with a change in calorific value; and signals w, d, v proportional to the weight flow rate obtained by the disturbance compensation signal acquisition means, _and A signal proportional to the amount of heat is obtained by multiplying the signal t _s − t _i of the difference in the detected temperature t _i of the side materials {w, d, v, t _s −
t _i } and enters this into a feedforward model to obtain a feedforward characteristic compensation signal; and a feedforward characteristic compensation signal obtained by this means and the feedback control. A running material temperature control device for a heat treatment furnace, comprising means for obtaining a setting signal for the secondary controller using the output.