Increasing Casting Speed without Mold Level Hunting Risk Using Switching Control

摘要

This paper is concerned with a new control approach for continuous casting intended to increase the production speed while avoiding dynamic bulging. In few words, the approach consists in using a set of simple PID controls, as those usually implemented in the standard continuous casting controls. The set may and actually does include settings such that their use for a specific steel grade or a high casting speed would lead the plant to dynamic bulging. An intelligent switching strategy is designed to prevent mold level hunting, this preserve smooth operation and yield a higher average casting speed than using only a "safe" PID setup. The method is based on the observation of the currents of the motors driving the rolls. However, differently from previous works, this information is not used to design an additional input signal, a feedforward, but to switch. It is also possible to adapt the casting speed not to use directly the motor current. Using a well tested simulator this method under realistic conditions yields an increase in production speed of about 20% (from slightly less 1.1m/min up to 1.3m/min). Due to its inherent simplicity, the method can easily take into account neglected dynamics or be adapted to other plants.