Synopsis : This paper describes walking control suppressing the lateral unstable movement of the strip in a hot strip finishing mill. The conventional method for controlling walking is well known as "load difference method", in which the measured load difference between the drive and operator sides of the rolling stand is fed back to the roll gap slant reference. However, analyzing the relationship between the feedback control gains of load difference and control effects, we found that the conventional method had a defect that the control effect extremely decreased, as the strip width became wide. Therefore, we developed a new control method that the manipulated value of the roll gap slant was determined based on the strip position measured by a newly developed measuring instrument. In this method, because the strip position sensor is equipped at the entry side of the controlled rolling stand with some distance, the measured strip position is not equal to that at the rolling stand, which is the controlled variable. We overcome the difficulty by applying the model predictive control having the function to predict a future value of the controlled variable and optimizing the manipulated value of the roll gap slant. The effectiveness of the new control method has been demonstrated in an actual plant.

Synopsis: To measure strip velocity accurately between the stands of the hot strip finishing mill is effective in keeping the stable production and improving the strip dimension control accuracy. Two laser doppler velocimeters has been installed at F4 stand exit and F5 stand exit for evaluating their durability and measurement accuracy. These velocimeters have achieved accurate and stable measurement in bad environment with water splash and high temperature at interstand of hot strip finishing mill by implementing the effective countermeasures to environment and improving the digital signal processing. F5 stand mass flow gage is calculated by using the F4 stand exit gage and the strip velocities measured by these velocimeters. The F4 stand exit gage is measured by existing interstand X-ray thickness gage. The evaluation results indicate that the mass flow thickness has been measured within 0.46% accuracy and will be able to apply to the mass flow AGC (Automatic Gage Control) at the hot strip finishing mill.

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In recent years, in order to reduce CO 2 emission and keep productivity in ironmaking process, high gas permeability and high reaction efficiency with maintaining stable operation are required in a blast furnace. To meet these requirements, it is important to control the burden material distribution and material mixed ratio accurately. A new tracking technique of burden materials in charging process by using RFID (Radio Frequency IDentification) tags that are characterized by non-contact ID code recognition has been developed. In this technique, the active RFID tags, built in the durable case imitating coke or ore particles, are putted on the charged materials and detected their ID code at several points on the way of charging route. Their tracking accuracy and detection success rate were evaluated at the actual blast furnaces. As a result, the nut coke imitated tag's detection ratio on the time series was good agreement with the nut coke mixed ratio measured by sampling at the nut coke mixed charging. By considering the RSSI (Received Signal Strength Indicator), the passing timing of the tag could be estimated accurately within 1.3 s (one sigma) on the belt-conveyor. In the top collection hopper, tags were detected at just passing and its detection success ratio was over 83% of all putted tags. These results indicated that the developed tracking technique of burden materials would be useful for controlling the burden material distribution accurately and improving the blast furnace operation.

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