Steel sheet temperature control device and temperature control method

A steel sheet temperature control device, comprising:

• a sheet temperature measurement unit that measures temperature of a steel sheet at an inlet side and an outlet side of a heating furnace including a plurality of heating zones disposed along a conveyance direction of the steel sheet;
• a furnace temperature measurement unit that measures furnace temperature of each of the heating zones;
• and
• a process computer configured to execute a process, the process including:
• calculating an influence coefficient representing temperature change of the steel sheet at the outlet side of the heating furnace in response to temperature change of the steel sheet at the inlet side of the heating furnace, and an influence coefficient representing temperature change of the steel sheet at the outlet side of the heating furnace in response to change in the furnace temperature of each of the heating zones, using a heating model equation capable of calculating the temperature of the steel sheet in the heating furnace, by inputting a set value of the temperature of the steel sheet at the inlet side of the heating furnace, and set values of the furnace temperature of each of the heating zones and sheet passing speed;
• setting a control model by inputting a furnace temperature change command value and outputting the furnace temperature of each of the heating zones and the temperature of the steel sheet at the outlet side of the heating furnace, by using the calculated influence coefficient, transfer time of the steel sheet until influence of furnace temperature change in each of the heating zones appears on the temperature of the steel sheet at the outlet side of the heating furnace, a time constant from when the furnace temperature change command value of each of the heating zones is output to when the furnace temperature is actually changed, and a variable representing unknown temperature disturbance to be applied to the temperature of the steel sheet at the outlet side of the heating furnace;
• estimating values of a state variable and a temperature disturbance variable of the control model at the same time, by inputting a deviation between an actual value of the temperature of the steel sheet at the inlet side of the heating furnace measured by the sheet temperature measurement unit and a set value, a deviation between an actual value of the temperature of the steel sheet at the outlet side of the heating furnace measured by the sheet temperature measurement unit and a set value, and a deviation between an actual value of the furnace temperature of each of the heating zones measured by the furnace temperature measurement unit and an initial set value;
• calculating a furnace temperature change amount of each of the heating zones under a constraint condition such that square sum of a deviation between a target value and the actual value of the temperature of the steel sheet at the outlet side of the heating furnace becomes minimum, by using the estimated values of the state variable and the temperature disturbance variable of the control model;
• and
• controlling a fuel flow rate used in each of the heating zones to achieve the calculated furnace temperature change amount.