JPS6114523B2 - - Google Patents

Description

[Detailed Description of the Invention] In a feedback control system where the controlled object moves at a certain speed and there is a certain distance between the operating section and the sensor that detects the controlled amount, the transfer time changes depending on the speed. When optimal adjustment is made to the control system at a certain speed, a hunting phenomenon occurs at lower speeds, and at higher speeds the control becomes slow in response, far from the optimal control state.

Conventionally, such control systems have adopted a control method that takes into account only the transfer time delay. This conventional method aims to perform optimal control in consideration of transfer time delays by detecting the speed of the controlled object and multiplying the difference between the target value, which is the deviation input of the control device, and the control amount. However, this method is successful only when the sensor detection delay etc. can be sufficiently ignored compared to the transfer time delay. In actual control systems, sensor detection delays and the like cannot often be ignored compared to transfer time delays, so optimal control has often not been achieved with conventional systems.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for controlling such a problem so that an optimum control state is always maintained no matter how the speed of the controlled object changes.

An example in which the present invention is applied to a plate thickness control system of a rolling mill shown in FIG. 1 will be described. FIG. 2 is a control block diagram in this case.

In Fig. 1, 1 is a rolling material to be controlled, 2 is a rolling mill which is an operation unit, 3 is a plate thickness detector which is a controlled variable, 4 is a rolling mill drive electric motor, and 5 is a rolling material to be controlled. 6 is a setter for plate thickness which is a target value, 7 is a plate thickness deviation calculator which is the difference between the target value and the control amount, 8 is a non-linear calculator which will be described later. 9 is a multiplier, 10 is an adjustment section of the control device, and 11 is a roll reduction control device of the rolling mill.

The transfer dead time T _L in Fig. 2 is calculated as follows, where L is the distance between the rolling mill 2 and the detector 3 in Fig. 1, and V is the speed of the rolled material 1, T _L =L/V... (1) becomes. Further, the series transfer function of the transfer dead time transfer function and the board thickness detector detection delay transfer function can be approximated as shown in equation (2).

The transfer function G _M of the reduction control device and the rolling mill is simplified here and is assumed to be G _M =1...(3), and the plate thickness adjuster makes the plate thickness deviation zero, so
If it has an integral characteristic, the closed loop transfer function G _c in FIG. 2 will be as shown in equation (4).

In the above equation, the optimal control conditions for this control system are S=
If the absolute value 1/1G _c 1 of the frequency transfer function obtained by setting jw is 1 in the widest possible frequency range, then 1/|G _c | ² must also be 1. Therefore, 1/|G _c | ² = 1+S ² {2T _I /K (T ₀ +L/V) - T _I ² /K ² }+S ⁴ T _I ² /K ² (T _p +L/V
) ² ...(5) Therefore, as many terms as possible in the polynomial in equation (5) must be zero.

2T _I /K (T _p +L/V) - T _I ² /K ² = O...
...(6) K=V・T _I /2(V・T _p +L) ...(7) Therefore, the value of the variable gain K in Fig. 2 is a function of the rolling material speed (V) (7) When given by the formula, this plate thickness control system performs optimal control in accordance with changes in the rolling material speed.

8 and 9 in Figure 1 are (7) for performing this optimal control.
These are a nonlinear arithmetic unit and a multiplier for calculating the variable gain K of the equation. The characteristics of this nonlinear arithmetic unit 8 are the third
The result will be as shown in the figure.

As described above, according to the present invention, the controlled object moves at a certain speed, such as the plate thickness control system or shape control system of rolling equipment, and there is a distance that cannot be ignored for control purposes between the operating section and the control amount detector. In a feedback control system, the variable gain is calculated along with the speed of the controlled object by taking into account the detection delay of the controlled variable detector in addition to the transfer time delay during which the controlled object moves the distance between the operating unit and the controlled variable detector. , this variable gain is
By multiplying by the difference between the target value and the control amount, which is the deviation input of the control system, it becomes possible to approach the optimal control state even more than the conventional method.

[Brief explanation of the drawing]

FIG. 1 is a conceptual diagram of an embodiment of the present invention, FIG. 2 is a block diagram thereof, and FIG. 3 is a characteristic diagram of a nonlinear arithmetic unit. In FIG. 1, 1 is a rolling material, 2 is a rolling machine,
3 is a plate thickness detector, 5 is a rolling speed generator, 6 is a plate thickness setter, 8 is a nonlinear arithmetic unit, 9 is a multiplier, 10 is an adjustment unit, and 11 is a roll reduction control device.

Claims (1)

[Scope of Claims] 1. A detector for detecting the thickness of a rolled material in a rolling mill is arranged at a distance L from an operating section of the rolling mill such that a non-negligible dead time occurs in control, and In a feedback control system in which a roll reduction control device is operated by a controller that integrates the deviation between a detected thickness value and a target thickness value from a setter over an integration time _T1 , the dead time and the thickness In order to perform optimal control considering the detector's post-detection time constant T ₀ ,
A rolling material speed V is detected, and the deviation is multiplied by a variable gain K corresponding to the relationship K=V・T ₁ /2 (V・T ₀ +L) according to the detected rolling material speed. Optimal control method for feedback control system.