Reduce disturbances caused by the soft reduction of the mold level In continuous casting using a PID and fuzzy controller

In the steel companies, continuous casting is used to make slabs from molten steel for following progress. In order to increase the quality of the slabs and guarantee the safety, the variation of the molten steel level in the mold should be decreased as much as possible. However, the adjustment mold level control is very difficult because the mold level control system is nonlinear, time varying and various unpredictable disturbances. Under normal conditions, proportional integral derivative (PID) control works quite well, but unusual conditions require manual action. Indeed, when the flow of molten steel into the mold increases unexpectedly, the PID controller is not always able to avoid large level changes that can even lead to mold overflow. Besides an stoppage to the casting production, high maintenance costs will be resulted, So a PID - fuzzy controller has been proposed using the expert knowledge of the operators for controlling the process during level problems. This PID-FUZZY level controller has a great ability to solve these problems. In compare to other works, using three number of input parameters in this PID-FUZZY level controller that affect deviations of mold level are seen. In the simulation, the closing/opening of the first segment of strand(soft reduction) that affect variations is considered and is shown to be overcome by the PID-FUZZY mould level controller. The simulation results show that the proposed PID - fuzzy controller in compare to conventional PID Controller, has better progress in adjustment of mold level during soft reduction.