JPH0332401B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention mainly relates to a method of controlling the angle of a looper in a hot rolling finishing mill or the like by adjusting the rotational speed of the rolls of the finishing mill.

Normally, the looper controls the strip tension between the stands and the loop amount to maintain the strip tension stably.The looper angle (specifically, the arm angle of the looper) is used to control the relative speed of the rolls on the mill stand. Control is performed by adjusting. Control of this looper angle is configured by a PID control system, and the first
The figure is a block diagram of a conventional looper angle control system, and FIG. 2 is a graph showing the characteristics of the open circuit transfer function of the entire control system. In Fig. 1, when the angle command value θref is set in the angle control system of the looper,
It is added to the currently set looper angle θ and proportional integral processing {transfer function: KP (1+1/sTL)
KP: proportional coefficient, TL: integration time, s: Laplace operator}, differential processing (transfer function: 1+sTD, TD:
Transfer function that can be expressed by the following equation (1)
Input to the speed controller of the rolling mill stand with Gn(s).

Gn(s)=Kn・ωn ² /s ² +2・ξ・sωn+ωn ² ...(1) However, Kn: gain constant ωn: natural frequency (rad/sec), ξ: damping coefficient Mill stand from speed control device A signal corresponding to the roll speed control amount v is output, and roll speed control is performed by adding together the strip speed influence amount as a disturbance, for example, the influence amount due to poor heat treatment, etc., and the influence amount due to a change in the backward movement rate. As a result, the looper moves at an angular velocity P(=dθ/
dt), and the looper angle becomes θ after passing through the integral element.
is set to θref and added to θref again, and the above process is repeated until the two match.

Characteristics of the speed control device and looper as described above,
That is, the phase and gain are approximated by a second-order lag system, and each natural frequency (rad/second) is ωn = 10 to 20 for a speed control device, and ωL = 20 for a looper.
5 to about 30, the characteristics of the open circuit transfer function G ₀ (s) of the entire control system, that is, its gain curve, are set as shown in FIG. The graph in Figure 2 shows the angular frequency ω (rad/sec) on the horizontal axis and the gain (dB) on the vertical axis.
It is shown below. Since the gain conditions for the corner frequency 1/TL and ωn for maintaining stability of such a control system are determined by equations (2) and (3), respectively, G ₀ (1/TL) ≧ 10 dB...( 2) G ₀ (ωn)≦−10dB (3) The crossing angular frequency ωc satisfies ωc≒ωn·1/3, and is set to a value as shown in equation (4).

ωc≦3～6……(4) Automatic thickness control (AGC) is performed in finishing mills, and when the roll opening changes rapidly, the stripping speed changes sharply, and for example, the stripping speed changes rapidly. If there is variation in thickness or variation in deformation resistance due to skid marks, etc., the advancing rate and backward rate change, and similarly, the strip speeds at the entrance and exit sides of the rolling mill in the finishing mill change sharply. When such a change in strip speed occurs, the amount of loop between the rolling mills changes. For example, if the tension is constant, the looper moves up and down, and the looper angle changes. However, as mentioned above, the response of the looper angle control cannot follow the crossing angular frequency ωc, which is about 3 to 6 rad/sec, and there is a gap between the change in the strip speed and the change in the looper angle. Since an integral element is involved, this causes a time delay. Conventional feedback control, which simply detects the looper angle and controls the roll speed to suppress this, inevitably results in a response delay, causing the strip tension and looper angle to become large. Change. Fluctuations in strip tension will change the thickness and width of the strip, making it impossible for the thickness control function to fully demonstrate its effectiveness. On the other hand, large fluctuations in the looper amount will cause operational problems such as triple bite and narrowing due to sideways slipping of the strip. Problems such as troubles may occur.

Conventionally, as described in Japanese Patent Publication No. 54-32629, the feedback gain for the looper motor and rolling roll motor is changed according to the value of the detected looper angle, and as the looper angle increases, the control gain is changed. Devices have been proposed that increase responsiveness.

However, this conventional device merely performs feedback control in which the control gain is changed according to the detected looper angle, and it is not possible to avoid problems such as the presence of skid marks in the rolled material or sudden roll opening in AGC. There was a problem in that it was not possible to eliminate the delay in control due to the involvement of an integral element between the rolling material speed and the looper angle.

The present invention has been developed in view of the above circumstances, and includes estimating the strip speed change based on the roll speed command value, the looper angle, or the looper angular velocity using a simulator when the strip speed changes due to disturbance. A speed command value corresponding to this estimated value is input to the roll speed control device, and the roll speed is controlled to stabilize the looper angle, thereby quickly responding to changes in strip speed caused by disturbances. Looper angle control The purpose is to provide a method.

The looper angle control method according to the present invention is a method of controlling the angle of the looper by adjusting the roll speed of a rolling mill stand with a speed control device. Alternatively, a simulator that detects the angular velocity and simulates the dynamic characteristics of the roll speed control device based on the angle or angular velocity of the looper and a speed command value for the speed control device and a simulator that simulates the dynamic characteristics of the looper are used to control the rolling material. The present invention is characterized in that a speed change amount is estimated, a speed command value corresponding to the estimated value is input to the speed control device, and the roll speed is controlled to correct a looper angle change due to disturbance.

The present invention will be specifically explained below based on the drawings.
FIG. 3 is a schematic diagram showing the implementation state of the method of the present invention, in which 1 and 2 indicate two adjacent stands in a finishing mill, 3 indicates a looper, and 4 indicates a strip. The looper 3 is located between the stands 1 and 2, and presses the strip 4 passed through from the direction of the white arrow upward from the bottom side of the strip 4, applying appropriate tension to the strip 4, and also attaches the strip 4 to the stands 1, 2. It is designed to ensure an appropriate amount of strip loop between the two. The looper 3 is constructed by having a roll 3c pivoted on the upper end of an arm 3b whose lower end is pivotally supported on a support base 3a, and an operating rod of a hydraulic cylinder 3d connected to the middle part of the arm 3b. The arm 3b is set at a required angle by operation.

5 is a speed control device of the finishing mill, and looper 3
The arm angle (hereinafter referred to as the looper angle) θ is detected based on the angle data input from the arm angle detector provided at the lower end of the arm 3b, and this detected looper angle or the looper angular velocity obtained from this is combined with a preset command value θref. Based on simulators 6 and 7
Estimate the disturbance, that is, the fluctuation of the strip speed,
A signal corresponding to the control amount is output to each motor control section 11, 12 of the mill stand.
6 is a simulator that simulates the dynamic characteristics of the speed control device 5, and 7 is a simulator that simulates the dynamic characteristics of the looper.These simulators 6 and 7 are designed to prevent strip distortion caused by disturbances in maintaining the looper angle stably. The responsiveness of the looper is improved by estimating the speed fluctuation and inputting a signal corresponding to this estimated value to the speed control device 5 as a speed command value. It is designed to stabilize the looper angle and strip tension.

These control processes will be explained in detail below based on the block diagram shown in FIG. FIG. 4 is a block diagram showing the angle control system of the looper. In FIG. 4, Gn(s) is the mill motor speed control device,
GL(s) indicates the dynamic characteristics of each looper. Now, if there is a disturbance ω, the looper angle θ changes due to GL(s) and the integral element 1/s.

This θ is fed back, the difference with θref is found, and the output x(s) is passed through each control element of Kp (1+1/sTL) and 1 ⁺ sTD to Gn(s), (s) simulator 6), GL ^* (s) (GL(s) simulator 7), and an integral element 1/s to calculate and output the estimated value θ ^* of the looper angle.

Incidentally, the disturbance ω is not input to either of the simulators 6 and 7, and instead, Δθ, which is the difference between θ and θ ^* , is passed through g ₁ and −g ₂ and 1/s to obtain the estimated disturbance value ω ^* is added to the input of GL ^* (s).

By feeding back Δθ to GL ^* (s) in this way, it is possible to converge the estimated disturbance value ω ^* to be equal to the disturbance ω to the rolling mill stand.

As described above, according to the present application, since the disturbance (ω) can be quickly estimated as the estimated value ω ^* , by directly compensating this to the speed control devices Gn (s), (Gn ^* (s)), it is possible to Disturbances can be corrected with quick response.

By using the simulators 6 and 7, strip speed fluctuations caused by disturbances can be calculated accurately and quickly, and this calculated value is sent to the roll speed control device 5.
As a result, the response of the roll speed control system, in other words, the looper angle control system, becomes faster, and excessive loop amount and tension fluctuations can be quickly dealt with.

FIG. 5 is a block diagram showing another embodiment of the present invention, except that in this embodiment, the looper angular velocity P is used instead of the looper angle θ shown in FIG. 4. This is substantially the same as the embodiment, and the same symbols are used for corresponding parts, and the explanation will be omitted.

In such control, the angular velocity of the looper is used instead of the looper angle θ, and the same looper angle control as shown in FIG. 4 using the looper angle θ can be performed.

The looper angle estimate θ ^* obtained using the simulators 6 and 7 in the angle control process shown in FIGS. 4 and 5,
The estimated angle value P ^* and the estimated disturbance value ω ^* are each given as follows. Now the transfer function of the speed control device 5
Gn(s), looper dynamics transfer function GL
(s) and simulators 6 and 7 corresponding to these
Assuming that the transfer functions Gn ^* (s) and GL ^* (s) are equal, the looper angle θ (s), the disturbance ω (s), the roll speed setting value x (s), the estimated value by the simulator θ ^* (s),
In the control method shown in FIG. 4, the relationship between ω ^* (s) can be expressed as in the following equations (5), (6), and (7).

θ(s)=1/s・GL(s) {x(s)・Gn(s)−ω(s)} ...(5) θ ^* (s)=1/s・GL(s)[x (s)・Gn(s)−ω＊(s)＋g ₁
{θ(s)−θ ^* (s)}]……(6) ω ^* (s)=−g ₂ {θ(s)−θ ^* (s)} ・1/s……(7) Looper angle The deviation Δθ=θ ^* −θ is given by the following equation (8) from equations (5) and (6).

Δθ(s)=1/s・GL(s) {−ω ^* (s) −g ₁ Δθ+ω(s)} ...(8) Substitute equation (7) for ω ^* (s) in equation (8) Then, Δθ(s)=1/s・GL(s) {−g ₂ /s ・Δθ(s) −g ₁・Δθ+ω(s)} ……(9) ∴Δθ(s) =S・ω( s)・GL(s)/s ² +g ₁ GL(s)・s+
g ₂・GL(s) ……(10) Also, from equations (7) and (10), ω ^* (s) = g ₂・ω(s)/s ² +g ₁ GL(s)・s+g ₂・GL (s
)...(11) On the other hand, in the control method shown in Fig. 5, the looper angle change rate P(s), disturbance ω(s), roll speed setting value x(s), and these estimated values by the simulator are The relationship between P ^* (s) and ω (s) is as follows (12),
It is given by equations (13) and (14).

P(s)=GL(s) {x(s)Gn(s)−ω(s)} ...(12) P ^* (s)=GL(s)[x(s)Gn(s)−ω ^* (s)+g
₁ {P(s) −P ^* (s)}] ...(13) ω ^* (s)=g ₂ {P(s)−P ^* (s)}・1/S ...(14) Looper's Angular velocity deviation ΔP (s) = P ^* (s) − P
(s) and ω ^* (s) are determined from equations (12) to (14) in the same manner as described above, as shown in equations (15) and (16) below.

ΔP(s)=GL(s){−ω ^* (s)−g ₁ ΔP(s)+
ω(s) = s・ω(s)・GL(s)/{1+g ₁・GL(s)}
s+g ₂・GL(s)……(15) ω ^* (s) =g ₂ ω(s)GL(s)/{1+g ₁ GL(s)}s+g ₂
GL (s) ... (16) If the gains g ₁ and g ₂ are appropriately selected from the above formulas (10) and (11) or (15) and (16), Δθ at t→∽
→ becomes 0, θ ^* (s) → θ (s), ω ^* (s) → ω
(s). g ₁ and g ₂ are obtained as follows.

For example, GL (s) = KL / (1 + sT ₀ ) (KL:
Assuming that the gain constant, T ₀ (time constant) = 1/ωL, substituting this into equations (10) and (11) yields equations (17) and (18).

Δθ(s) = s・ω(s)/TL・s ³ +s ² +KL・g ₁・s+g ₂・KL ……(17) ω ^* (s) = ω(s)/TL・s ³ +s ² +KL・g ₁・s＋g ₂・KL ……(18) Similarly, substituting into equations (15) and (16), (19),
It becomes as shown in equation (20).

ΔP=s・ω(s)/TL・s ² +(KLg ₁ +1)・s+g ₂ K
L ... (19) ω ^* (S) = g ₂ ω (s) / TL・s ² + (KLg ₁ +1)・s+g ² KL ... (20) Therefore, ω ^* ( In order to make the response of s) faster than the response of the control system, assuming that TL≪g ₂ KL (take g ₂ sufficiently large), equation (18) becomes a second-order lag element, as shown in Figure 4. In the control method, ω ₀ ≒√ ₂ or ζ≒KLg ₁ /2ω ₀ , and ζ
= 0.7, ω ₀ ≫ In order to satisfy TL, g ₂ = (10 ³ ~ 10 ⁴ )KL ... (21) g ₁ = 1.4ω ₀ /KL = 1.4√ ₂ ... (22) It turns out.

In addition, in the control method shown in Fig. 5, ω ₀ ≒√ _{2 0} and ζ≒(KLg ₁ +1)/2ωn, so g ₁ and g ₂ can be expressed as follows (23) in the same way as above:
It is sufficient to do it as shown in equation (24).

g ₂ = (10 ³ ~ 10 ⁴ ) T ₀ /KL ... (23) g ₁ = 1.4√ ₂ ... (24) As described above, in the method of the present invention, the looper angle is controlled as described above. The response frequency ωc of the simulator is normally about 3 to 6 (rad/sec), but when using the method of the present invention, the response frequency ω ₀ of the simulator is determined by the following equation (25) from equations (21) and (23). Thus, ω ₀ ≒√10 ³ to 10 ⁴ =31 to 100 rad/sec (25) The response frequency can be improved by about 10 times.

Therefore, if the speed command is directly compensated with the estimated disturbance value ω ^* obtained by the simulators 6 and 7, a faster response will naturally be obtained compared to the response in the conventional control method.

FIG. 6 is a graph showing the results of a comparative test between the method of the present invention and the conventional method described in Japanese Patent Publication No. 54-32629. Further, FIG. 6b shows the change in the looper angle, and FIG. 6c shows the amount of change in the rolling mill speed command. As is clear from this, in contrast to the step-like rolling mill speed change shown in Figure 6a, in the conventional method, the rolling mill speed command changes in a ramp-like manner, resulting in a large looper angle change, as shown in Figure 6b. It takes approximately 2 seconds to complete the correction.

On the other hand, in the method of the present invention, when a rolling mill speed change occurs, it is immediately estimated and the rolling mill speed command is compensated for by feed forward, so that the amount of change in the rolling mill speed command is The step-like output is almost the same as the rolling mill speed change shown in Figure 6a, and as a result, the looper angle change is suppressed to an extremely small level as shown in Figure 6b, and the time it takes to regain stability is approximately 0.3 seconds. I know it will be done.

When the strip speed is changed due to a disturbance, a simulator is used to estimate the amount of change in the strip speed due to the disturbance based on the looper angle or looper angular velocity and the speed command value for the roll speed control device of the mill stand, and this estimated value is used as the speed. Since it is input to the control device, the looper can quickly respond to changes in strip speed caused by skid marks or variations in entry side plate thickness, and changes in reverse rate, suppressing excessive loop amount and tension fluctuations. As a result, the present invention is of great benefit in preventing operational troubles and improving product quality.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a general looper angle control system, Fig. 2 is a graph showing the characteristics of the open circuit transfer function of the entire control system, Fig. 3 is a schematic diagram showing the implementation state of the method of the present invention, FIG. 4 is a block diagram showing a control mode in the method of the present invention, FIG. 5 is a block diagram showing another control mode in the method of the present invention, and FIG. 6 shows the results of a comparative test between the method of the present invention and the conventional method. It is a graph. 1, 2...mil stand, 3...roopa, 4...
...Hydraulic cylinder, 5...Speed control device, 6,7...
...Simulator.

Claims (1)

[Claims] 1 In a method of controlling the looper angle by adjusting the roll speed of a rolling mill stand with a speed control device, when the looper angle changes due to a change in the rolling material speed due to a disturbance, the looper angle or angular velocity is detected and the looper The amount of speed change of the rolled material is estimated using a simulator that simulates the dynamic characteristics of the roll speed control device and a simulator that simulates the dynamic characteristics of the looper based on the angle or angular velocity of the roll speed control device and the speed command value for the speed control device. A method for controlling a looper angle, comprising inputting a speed command value corresponding to an estimated value to the speed control device and controlling the roll speed to correct changes in the looper angle due to disturbances.