JPS625684B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to coiling temperature control of a rolled steel plate after hot rolling, and relates to a coiling temperature control method that always performs feedback control with an optimal gain and improves the accuracy of the coiling temperature. .

Generally, in coiling temperature control, as shown in FIG. Feed forward control in which the calculation device 5 calculates the required water injection amount based on the sent finishing temperature signal 12 and outputs the valve control signal 14 to control the water injection valves of the first water injection equipment 6A, 6B, and the front of the coiler 9. Based on the winding temperature signal 13 sent from the winding thermometer 7 installed at
Feedback control is also used to control the water injection valves of the second water injection equipment 8A, 8B, which can finely adjust the amount of water using the fine water injection control signal 15 calculated in .

Although the feedforward control described above has no direct relation to the present invention, its outline will be described as follows. That is, a method not shown in FIG.
For example, the target winding temperature can be determined from various data related to the rolled material to be controlled, which are read by a data link from another computer to the arithmetic unit 5, or by a constant setting device, etc., and the speed, finishing temperature, etc. of the rolled material. Calculate the required amount of water to inject, decide which bank should be injected according to the result, turn on the valve,
The required cooling length is obtained by off-controlling.

The effectiveness of this feed-forward control is not only greatly affected by the control model used, but also by various disturbances such as fluctuations in finishing temperature, sudden changes in rolling speed, turning on and off water spray, and increases and decreases in water injection amount. It is very difficult to achieve the target winding temperature with sufficient accuracy because of the discontinuity of the winding temperature. For this reason, it is common to use feedback control in combination. However, in the past, it has been difficult to perform sufficient feedback control, especially for such objects with large dead times, because the feedback control method and/or the control gain value has been inappropriate.

The present invention improves the accuracy of coiling temperature control by changing the control gain of coiling temperature feedback control according to the thickness of the rolled material, rolling speed, etc., and always performing feedback control with the optimum gain. The purpose of the present invention is to provide a winding temperature control method.

The present invention will be described below based on an embodiment shown in the drawings. FIG. 2 is a block diagram related to feedback control in the winding temperature control system shown in FIG.
is the transfer delay from the cooling device to the winding thermometer, 25
indicates the winding thermometer, and 26 indicates the winding target temperature 101.
and the winding temperature detection value 104.
7 is a subtractor for obtaining the difference between the rolled material temperature 102 at the entrance of the second water injection equipment (for feedback control) and the temperature drop 105 due to the water injection equipment, 103 is the temperature at the winding thermometer, 106 is the required number of water injection valves, 107 represents the cooling length.

In the figure, the transfer function corresponding to each block has the following form. That is, the well-known proportionality -
When the integral control law is adopted, the control block 21 is...K ₁ (1+T ₁ S)/S...(0) The spray valve 22 is...K ₂ /1+T ₂ S・e ^-T ' ^2S ...(1) The cooling process 23 is...K ₃ /1+T ₃ S...(2) The transfer delay 24 is...K ₄ e ^-T4S ...(3) The winding thermometer 25 is...K ₅ /1+T ₅ S...( 4) Here, K ₁ is the control proportional gain, T ₁ is the integral gain K ₂ , T ₂ , T′ ₂ is the gain, time constant, and control delay of the spray valve operating section, and K ₃ , T ₃ is the gain of the cooling process. , time constant, K ₄ is the degree of attenuation of the winding temperature with respect to the water injection equipment outlet temperature, T ₄ is the transfer delay time,
K ₅ and T ₅ are the winding thermometer gain and time constant, and S is the Laplace operator.

Each of these parameters can be determined as follows. First, K ₂ is the cooling length per valve of the water injection cooling system, so K ₂ = l/
N, where l: cooling length (m), N: number of valves (pieces), _K3 is the amount of temperature drop per unit cooling length (corresponding to the amount of water injected), and can be derived as follows. The temperature of the rolled material at the entrance and exit of the water injection equipment (during water cooling) is T _E and T _O ; the cooling water temperature is T _W ;
The cooling section is l; the plate thickness is h; the running speed is V; the heat transfer coefficient of cooling water is α; the specific heat of the rolled material is c; the density is ρ
Then, equation (6) holds true.

α/cρl/hv=ln, T _E −T _W /T _O −T _W ……
(6) ln is a symbol representing natural logarithm (loge). (6)
If we transform the right side of the equation, we get equation (6)′.

α/cρl/hv=ln(1+T _E −T _O /T _O −T _W )
≒T _E −T _O /T _O −T _W ……(6)′ 〓T _E −T _O ≪T _O −T _W Therefore, T _E −T _O ≒α/cρl/hv (T _O −T _W ) ...(7) If the winding target temperature T _c is approximately T _O ≒ T _c /
K ₄ and K ₃ is as shown in equation (8).

Also, strictly speaking, K ₄ is influenced by h and v,
Although the relationship is not as simple as above, it is sufficient as an approximation. T ₃ is also approximately a constant. _T4
T ₄ =L/V from the average distance L between the cooling device and the winding thermometer. Furthermore, it can be easily seen that K ₄ is approximately 1.0, and K ₅ =1.0 with sufficient precision.

As an example, consider a system with the following constants. K ₂ = 1.0m/number of valves, L = 25m, T ₂ =
0.5sec, T' ₂ = 1.5sec, T ₃ = 2.0sec, K ₄ = 1.0, K ₅
= 1.0, T ₅ = 0.3sec, c = 0.2Kcal/Kg・deg, α
= 1000 Kcal/m ² hrdeg, ρ = 7800 Kg/m ³ , and if the integral gain T ₁ of the control block is taken equal to T ₃ , the open loop transfer function GH of the system is GH = _Ke ^{- (T4 + 1.5 ) S} / S(1+0.3S)(
1+0.5S)...(9) It is stable if this loop gain K is selected appropriately. For example, set K so that the phase margin is 45°.
can be chosen, but in this case K is a function of T ₄ . Curve 30 in FIG. 3 illustrates the relationship between K and T ₄ calculated from the gain and phase angle of the open-loop frequency transfer relationship under the condition of a phase margin of 45° for the above example. If this curve is regarded as a part of a hyperbola, K can be approximated as a function of T ₄ using equation (10).

K=A/T ₄ +B+C...(10) Here, A, B, and C are constants. To find this, select three points on this curve, read the coordinates of these three points, and substitute them for T ₄ and K in equation (10), respectively, and create three simultaneous equations regarding A, B, and C. You can easily find it by solving. The curves shown in Figure 3 may differ slightly depending on the conditions of the water injection equipment and rolling material, but the shapes are the same and can all be expressed by equation (10) using the above method. In this example, A=
0.82, B=1.50, and C=0.02.

On the other hand, from Figure 2, loop gain K = K ₁・K ₂・
K ₃・K ₄・K ₅ , and by substituting the above K ₁ to K ₅ , K=K ₁ l/Nα/cρT _c −T _W /hV... (11) (10), (11) and the above Control gain K ₁ from the definition of T ₄
is K ₁ = KDV ... (12) where D = CρhN/α (T _c - T _W )l (N: number of valves of water injection equipment), and for one rolled material, plate thickness h, winding Since the target temperature T _c and the cooling water temperature T _W can be considered constant, D can be treated as a constant.
Therefore, in this example, the control gain K ₁ is The transfer function of the control block is equation (0), and if this is inversely transformed by Laplace, the winding temperature deviation △T _c
(°C) as an input, the number n of valves as an output is given by n=K ₁ (T ₁ △T _c +∫ ^t ₀ △T _c dt) (13).

As mentioned above, when proportional/integral control is performed in the coiling temperature feedback control in the above example system, the thickness of the rolled material hmm, the running speed V
m/min From the winding target temperature T _c ℃ and the cooling water temperature T _W ℃, using K ₁ calculated according to equation (12)′, n=K ₁ (2.0△T _c +∫ ^t ₀ △T _cdt ) ...(14) Here, △T _c : Winding temperature deviation (℃), t : Current time (sec), (however, the number n of vernier valves (based on the tip of the target coil) is made positive or negative. By turning on and off accordingly, stable and responsive control can be achieved.

Next, other embodiments of the present invention will be described. That is, the same effect can be obtained even if sampling control is adopted instead of the continuous control. In this case, the number of control valves is Here, △t is the sampling period (sec), △T
_ci is the winding temperature deviation ΔTc at time i.

Even if a differential element is added in this embodiment and the previous embodiment, the same control as described above is possible. Of course, in this case, the shapes of K ₁ and n may change somewhat, but this does not depart from the scope of the present invention. Furthermore, to show another embodiment of the present invention, from the above formula (12), K ₁ is (T _c
−T _W ), but T _c is approximately
Since T _{W is 500 to 600°C, and T W} is 20 to 40°C, there is no problem in setting this to a constant value, for example, T _c −T _W ≈550°C. At this time, K ₁ becomes a function only of h and V.

As is clear from the above explanation, if the control block and its control gain are determined according to the present invention and applied to coiling temperature feedback control, the deviation from the target coiling temperature can be minimized over the entire length of the rolled material. It is possible to obtain a small hot-rolled coil, that is, an excellent product with less variation in mechanical properties and workability. It goes without saying that it is desirable to apply normal feedback control in combination with the feedback control according to the present invention.

In this way, according to the present invention, the control gain of the coiling temperature feedback control is changed according to the rolled plate thickness, rolling speed, etc., and the feedback control is always performed with the optimum gain, thereby improving the accuracy of the coiling temperature. In particular, since the control gain is determined by actively considering the transfer delay time, a remarkable effect on high-speed rolling control can be expected.

[Brief explanation of the drawing]

Figure 1 is a configuration diagram of the winding temperature control system, Figure 2
3 is a diagram showing a winding temperature feedback control block diagram, and FIG. 3 is a diagram showing the relationship between the rolling material transfer delay time _T4 and the loop gain K shown in FIG. 2 in one embodiment of the present invention. 1... Final stand of finishing rolling mill, 2... Rolled material, 3... Speed detector, 4... Finishing thermometer, 5...
... Arithmetic device, 6... First water injection equipment, 7... Winding thermometer, 8... Second water injection equipment (fine adjustment possible), 11
...Rolling speed signal, 12 ... Finishing temperature signal, 13
... Winding temperature signal, 21 ... Arithmetic control device, 22
... spray valve, 23 ... cooling process, 2
4... Transfer delay, 25... Winding thermometer, 26,2
7...Subtractor, 101...Target winding temperature signal, 1
02...Rolled material temperature at the entrance of the second water injection equipment, 103
... Coiling temperature signal, 104 ... Coiling temperature signal detection value, 105 ... Rolled material temperature drop signal by second water injection equipment, 106 ... Number of second water injection equipment control valves,
107...Cooling length signal, 30...Transfer delay time
A curve showing the relationship between _T4 and loop gain K.

Claims (1)

[Scope of Claims] 1. The water injection operation of the water injection equipment is controlled according to the difference between the actual value of the coiling temperature of the hot rolling mill and the target coiling temperature value, so that the coiling temperature of the rolled material is adjusted to the target coiling temperature. In a feedback control system that performs control to match the temperature, the transfer delay time of the rolled material between the water injection equipment and the temperature detector that detects the coiling temperature is T (seconds).
Then, the loop gain K at which the feedback control system is stable is determined from the following formula: K=A/T+B+C However, A, B, and C are determined depending on the conditions of the water injection equipment and the rolled material. The control gain K _{1 is obtained by multiplying the above loop gain K by the rolling speed V (m/min) and the constant D obtained by the following formula. K 1 =} KDV where D = cρhN/α (T _c - T _w ) l c: Specific heat of rolled material (kcal/Kg℃) ρ: Density of rolled material (Kg/m ³ ) h: Plate thickness (m) N: Number of valves in water injection equipment α: Heat transfer coefficient between rolled material and water (kcal/m ² hr°C) _Tc : Target winding temperature (°C) _Tw : Cooling water temperature (°C) l: Cooling length of water injection equipment (m) Feedback control of the water injection operation of the water injection equipment is performed based on the following: Coiling temperature control method in a rolling mill.