Rolling control system and rolling control method

1. A rolling control system comprising:

a rolling stand; and

a rolling controller configured to execute speed control of which a control operation terminal is speed of a material to be rolled in an entry side of the rolling stand and roll gap control of which a control operation terminal is a roll gap of the rolling stand,

wherein the rolling controller includes:

a first plate thickness control part configured to execute roll gap and plate thickness control that is roll gap control to control a plate thickness of the material to be rolled in a delivery side of the rolling stand;

a second plate thickness control part configured to execute speed and plate thickness control that is speed control to control the plate thickness;

a first tension control part configured to execute speed and tension control to control a tension of the material to be rolled in the entry side of the rolling stand;

a second tension control part configured to execute roll gap and plate tension control to control the tension; and

a control selection part configured to select the speed and tension control and the roll gap and plate thickness control if rolling speed is less than a boundary value, while selecting the roll gap and plate tension control and the speed and plate thickness control if the rolling speed is greater than or equal to the boundary value,

wherein the control selection part is further configured to:

if the rolling speed rises across the boundary value at a startup of the rolling stand, set a speed correction amount to zero and then output it to the second tension control part such that the speed correction amount in the speed and tension control before a transboundary is not reflected to a calculation executed in the speed control amount of the rolling speed at the transboundary; and

if the rolling speed rises across the boundary value at the startup of the rolling stand, calculate a roll gap correction amount according to the speed correction amount and then output it to the second tension control part such that the speed correction amount is reflected to a calculation of a roll gap control amount executed in the roll gap and plate tension control at the transboundary,

wherein the control selection part includes:

a hold circuit configured to store the speed correction amount output in the speed and tension control from the first tension control part;

a trigger circuit configured to output a trigger signal when the rolling speed is equal to or greater than the boundary value; and

a ramp circuit configured to, when the trigger signal is output from the trigger circuit, calculate the roll gap correction amount according to the speed correction amount based on the speed correction amount output in the speed and tension control at which the trigger signal is output from the trigger circuit.

2. The rolling control system according to claim 1 , wherein

the roll gap control amount output from the first plate thickness control part is input to the roll gap control, before the trigger signal is output from the trigger circuit, and

the input of the roll gap control amount output from the first plate thickness control part is blocked by a switch, after the trigger signal is output from the trigger circuit.

3. The rolling control system according to claim 2 , wherein

the roll gap correction amount calculated by the ramp circuit is added to the roll gap control amount output from the second tension control part, and the combined amount of the roll gap correction amount calculated by the ramp circuit and the roll gap control amount output from the second tension control part is input to the roll gap control, after the trigger signal is output from the trigger circuit.

4. The rolling control system according to claim 1 , wherein the control selection part further includes another ramp circuit and a limiter,

a speed control amount output from the first tension control part and a speed correction amount that is used for calculation of the speed control amount is input to the other ramp circuit, and

the limiter is configured to input, to the speed control, the speed control amount output from the first tension control part, before the trigger signal is output from the trigger circuit.

5. The rolling control system according to claim 4 , wherein

the limiter inputs an upper restriction parameter to the speed control, under a condition that the speed control amount output from the first tension control part meets the upper restriction.

6. The rolling control system according to claim 4 , wherein

the limiter inputs, to the speed control, a speed control amount output from the second plate thickness control part, after the trigger signal is output from the trigger circuit.

7. The rolling control system according to claim 6 , wherein

the limiter inputs an upper restriction parameter to the speed control, under a condition that the speed control amount output from the second plate thickness control part meets the upper restriction.

8. The rolling control system according to claim 4 , wherein

the other ramp circuit is configured to reset the speed control amount output from the first tension control part and the speed correction amount that is used for calculation of the speed control amount, after the trigger signal is output from the trigger circuit.

9. A rolling control method comprising:

executing speed control of which a control operation terminal is rolling speed; and

executing roll gap control of which a control operation terminal is a roll gap of a rolling stand,

wherein the roll gap control includes:

roll gap and plate thickness control which is the roll gap control to control a plate thickness of a material to be rolled in a delivery side of the rolling stand; and

roll gap and plate tension control which is the roll gap control to control a tension of the material to be rolled in an entry side of the rolling stand,

wherein the speed control includes:

speed and tension control which is the speed control to control the tension; and

speed and plate thickness control which is the speed control to control the plate thickness,

wherein the rolling control method further comprising:

selecting, if rolling speed of the material to be rolled is less than a boundary value, the speed and tension control and the roll gap and plate thickness control;

selecting, if the rolling speed is greater than or equal to the boundary value, the roll gap and plate tension control and the speed and plate thickness control;

setting a speed correction amount to zero, if the rolling speed rises across the boundary value at the startup of the rolling stand, such that the speed correction amount in the speed and tension control before a transboundary is not reflected to a calculation executed in the speed control amount of the rolling speed at the transboundary; and

calculating, if the rolling speed rises across the boundary value at the startup of the rolling stand, a roll gap correction amount according to the speed correction amount such that the speed correction amount is reflected to a calculation of a roll gap control amount executed in the roll gap and plate tension control at the transboundary,

wherein the rolling control method further comprising:

storing the speed correction amount output in the speed and tension control; and

outputting a trigger signal when the rolling speed is equal to greater than the boundary value,

wherein, when calculating the roll gap correction amount according to the speed correction amount, the roll gap correction amount is calculated based on the speed correction amount output in the speed and tension control at which the trigger signal is output.